From 3d168c28f61565856f5d4726bf42235346848d5b Mon Sep 17 00:00:00 2001
From: Tamme Dittrich <tamme@tweedegolf.com>
Date: Mon, 23 Sep 2024 15:20:23 +0200
Subject: [PATCH 01/14] Improve assembly test for CMSE ABIs

This ensures the code-gen for these ABIs does not change silently.

Co-authored-by: Folkert <folkert@folkertdev.nl>
---
 tests/assembly/cmse.rs | 86 +++++++++++++++++++++++++++++++++++++++---
 1 file changed, 81 insertions(+), 5 deletions(-)

diff --git a/tests/assembly/cmse.rs b/tests/assembly/cmse.rs
index acad77b251357..e0ada8dc2f15c 100644
--- a/tests/assembly/cmse.rs
+++ b/tests/assembly/cmse.rs
@@ -1,6 +1,9 @@
+//@ revisions: hard soft
 //@ assembly-output: emit-asm
-//@ compile-flags: --target thumbv8m.main-none-eabi --crate-type lib -Copt-level=1
-//@ needs-llvm-components: arm
+//@ [hard] compile-flags: --target thumbv8m.main-none-eabihf --crate-type lib -Copt-level=1
+//@ [soft] compile-flags: --target thumbv8m.main-none-eabi --crate-type lib -Copt-level=1
+//@ [hard] needs-llvm-components: arm
+//@ [soft] needs-llvm-components: arm
 #![crate_type = "lib"]
 #![feature(abi_c_cmse_nonsecure_call, cmse_nonsecure_entry, no_core, lang_items)]
 #![no_core]
@@ -9,15 +12,88 @@ pub trait Sized {}
 #[lang = "copy"]
 pub trait Copy {}
 
-// CHECK-LABEL: __acle_se_entry_point
-// CHECK: bxns
+// CHECK-LABEL: __acle_se_entry_point:
+// CHECK-NEXT: entry_point:
+//
+// Write return argument (two registers since 64bit integer)
+// CHECK: movs r0, #0
+// CHECK: movs r1, #0
+//
+// If we are using hard-float:
+// * Check if the float registers were touched (bit 3 in CONTROL)
+// hard: mrs     [[REG:r[0-9]+]], control
+// hard: tst.w   [[REG]], #8
+// hard: beq     [[LABEL:[\.a-zA-Z0-9_]+]]
+//
+// * If touched clear all float registers (d0..=d7)
+// hard: vmov    d0,
+// hard: vmov    d1,
+// hard: vmov    d2,
+// hard: vmov    d3,
+// hard: vmov    d4,
+// hard: vmov    d5,
+// hard: vmov    d6,
+// hard: vmov    d7,
+//
+// * If touched clear FPU status register
+// hard: vmrs    [[REG:r[0-9]+]], fpscr
+// hard: bic     [[REG]], [[REG]], #159
+// hard: bic     [[REG]], [[REG]], #4026531840
+// hard: vmsr    fpscr, [[REG]]
+// hard: [[LABEL]]:
+//
+// Clear all other registers that might have been used
+// CHECK: mov r2,
+// CHECK: mov r3,
+// CHECK: mov r12,
+//
+// Clear the flags
+// CHECK: msr apsr_nzcvq,
+//
+// Branch back to non-secure side
+// CHECK: bxns lr
 #[no_mangle]
 pub extern "C-cmse-nonsecure-entry" fn entry_point() -> i64 {
     0
 }
 
+// NOTE for future codegen changes:
+// The specific register assignment is not important, however:
+// * all registers must be cleared before `blxns` is executed
+//     (either by writing arguments or any other value)
+// * the lowest bit on the address of the callee must be cleared
+// * the flags need to be overwritten
+// * `blxns` needs to be called with the callee address
+//     (with the lowest bit cleared)
+//
 // CHECK-LABEL: call_nonsecure
-// CHECK: blxns
+// Save callee pointer
+// CHECK: mov r12, r0
+//
+// All arguments are written to (writes r0..=r3)
+// CHECK: movs r0, #0
+// CHECK: movs r1, #1
+// CHECK: movs r2, #2
+// CHECK: movs r3, #3
+//
+// Lowest bit gets cleared on callee address
+// CHECK: bic r12, r12, #1
+//
+// Ununsed registers get cleared (r4..=r11)
+// CHECK: mov r4,
+// CHECK: mov r5,
+// CHECK: mov r6,
+// CHECK: mov r7,
+// CHECK: mov r8,
+// CHECK: mov r9,
+// CHECK: mov r10,
+// CHECK: mov r11,
+//
+// Flags get cleared
+// CHECK: msr apsr_nzcvq,
+//
+// Call to non-secure
+// CHECK: blxns r12
 #[no_mangle]
 pub fn call_nonsecure(
     f: unsafe extern "C-cmse-nonsecure-call" fn(u32, u32, u32, u32) -> u64,

From cfb8419900c1511b09320d70105128ce13de6e71 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Mon, 23 Sep 2024 18:07:42 -0400
Subject: [PATCH 02/14] Separate collection of crate-local inherent impls from
 error reporting

---
 .../src/coherence/inherent_impls.rs           | 34 ++++----
 .../src/coherence/inherent_impls_overlap.rs   |  3 +-
 .../rustc_hir_analysis/src/coherence/mod.rs   |  6 +-
 .../src/hir_ty_lowering/errors.rs             |  2 +-
 .../src/hir_ty_lowering/mod.rs                |  2 +-
 compiler/rustc_hir_analysis/src/lib.rs        |  2 +-
 compiler/rustc_hir_typeck/src/expr.rs         |  1 -
 compiler/rustc_hir_typeck/src/method/probe.rs |  4 +-
 .../rustc_hir_typeck/src/method/suggest.rs    | 11 +--
 .../src/rmeta/decoder/cstore_impl.rs          |  4 +-
 compiler/rustc_metadata/src/rmeta/encoder.rs  |  4 +-
 compiler/rustc_middle/src/query/erase.rs      |  6 ++
 compiler/rustc_middle/src/query/mod.rs        | 14 ++-
 compiler/rustc_middle/src/ty/trait_def.rs     | 20 +----
 compiler/rustc_monomorphize/src/collector.rs  |  2 +-
 .../rustc_resolve/src/late/diagnostics.rs     |  6 +-
 .../ui/const-generics/wrong-normalization.rs  |  1 -
 .../const-generics/wrong-normalization.stderr | 16 +---
 tests/ui/impl-trait/where-allowed.rs          |  3 +-
 tests/ui/impl-trait/where-allowed.stderr      | 86 ++++++++-----------
 tests/ui/traits/incoherent-impl-ambiguity.rs  | 14 +++
 .../traits/incoherent-impl-ambiguity.stderr   | 11 +++
 22 files changed, 127 insertions(+), 125 deletions(-)
 create mode 100644 tests/ui/traits/incoherent-impl-ambiguity.rs
 create mode 100644 tests/ui/traits/incoherent-impl-ambiguity.stderr

diff --git a/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs b/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
index c07d8009aa56c..dfb3c088afb0c 100644
--- a/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
@@ -22,36 +22,38 @@ use crate::errors;
 pub(crate) fn crate_inherent_impls(
     tcx: TyCtxt<'_>,
     (): (),
-) -> Result<&'_ CrateInherentImpls, ErrorGuaranteed> {
+) -> (&'_ CrateInherentImpls, Result<(), ErrorGuaranteed>) {
     let mut collect = InherentCollect { tcx, impls_map: Default::default() };
+
     let mut res = Ok(());
     for id in tcx.hir().items() {
         res = res.and(collect.check_item(id));
     }
-    res?;
-    Ok(tcx.arena.alloc(collect.impls_map))
+
+    (tcx.arena.alloc(collect.impls_map), res)
 }
 
-pub(crate) fn crate_incoherent_impls(
+pub(crate) fn crate_inherent_impls_validity_check(
     tcx: TyCtxt<'_>,
-    simp: SimplifiedType,
-) -> Result<&[DefId], ErrorGuaranteed> {
-    let crate_map = tcx.crate_inherent_impls(())?;
-    Ok(tcx.arena.alloc_from_iter(
+    (): (),
+) -> Result<(), ErrorGuaranteed> {
+    tcx.crate_inherent_impls(()).1
+}
+
+pub(crate) fn crate_incoherent_impls(tcx: TyCtxt<'_>, simp: SimplifiedType) -> &[DefId] {
+    let (crate_map, _) = tcx.crate_inherent_impls(());
+    tcx.arena.alloc_from_iter(
         crate_map.incoherent_impls.get(&simp).unwrap_or(&Vec::new()).iter().map(|d| d.to_def_id()),
-    ))
+    )
 }
 
 /// On-demand query: yields a vector of the inherent impls for a specific type.
-pub(crate) fn inherent_impls(
-    tcx: TyCtxt<'_>,
-    ty_def_id: LocalDefId,
-) -> Result<&[DefId], ErrorGuaranteed> {
-    let crate_map = tcx.crate_inherent_impls(())?;
-    Ok(match crate_map.inherent_impls.get(&ty_def_id) {
+pub(crate) fn inherent_impls(tcx: TyCtxt<'_>, ty_def_id: LocalDefId) -> &[DefId] {
+    let (crate_map, _) = tcx.crate_inherent_impls(());
+    match crate_map.inherent_impls.get(&ty_def_id) {
         Some(v) => &v[..],
         None => &[],
-    })
+    }
 }
 
 struct InherentCollect<'tcx> {
diff --git a/compiler/rustc_hir_analysis/src/coherence/inherent_impls_overlap.rs b/compiler/rustc_hir_analysis/src/coherence/inherent_impls_overlap.rs
index 43b9093ecac82..b8066b4b47d90 100644
--- a/compiler/rustc_hir_analysis/src/coherence/inherent_impls_overlap.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/inherent_impls_overlap.rs
@@ -177,8 +177,7 @@ impl<'tcx> InherentOverlapChecker<'tcx> {
             return Ok(());
         }
 
-        let impls = self.tcx.inherent_impls(id.owner_id)?;
-
+        let impls = self.tcx.inherent_impls(id.owner_id);
         let overlap_mode = OverlapMode::get(self.tcx, id.owner_id.to_def_id());
 
         let impls_items = impls
diff --git a/compiler/rustc_hir_analysis/src/coherence/mod.rs b/compiler/rustc_hir_analysis/src/coherence/mod.rs
index 185f3176f0789..b25406583f6c4 100644
--- a/compiler/rustc_hir_analysis/src/coherence/mod.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/mod.rs
@@ -124,7 +124,10 @@ fn enforce_empty_impls_for_marker_traits(
 
 pub(crate) fn provide(providers: &mut Providers) {
     use self::builtin::coerce_unsized_info;
-    use self::inherent_impls::{crate_incoherent_impls, crate_inherent_impls, inherent_impls};
+    use self::inherent_impls::{
+        crate_incoherent_impls, crate_inherent_impls, crate_inherent_impls_validity_check,
+        inherent_impls,
+    };
     use self::inherent_impls_overlap::crate_inherent_impls_overlap_check;
     use self::orphan::orphan_check_impl;
 
@@ -133,6 +136,7 @@ pub(crate) fn provide(providers: &mut Providers) {
         crate_inherent_impls,
         crate_incoherent_impls,
         inherent_impls,
+        crate_inherent_impls_validity_check,
         crate_inherent_impls_overlap_check,
         coerce_unsized_info,
         orphan_check_impl,
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
index 5e3203e847368..5775a8867b16a 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
@@ -1028,7 +1028,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 ..
             }) = node
             && let Some(ty_def_id) = qself_ty.ty_def_id()
-            && let Ok([inherent_impl]) = tcx.inherent_impls(ty_def_id)
+            && let [inherent_impl] = tcx.inherent_impls(ty_def_id)
             && let name = format!("{ident2}_{ident3}")
             && let Some(ty::AssocItem { kind: ty::AssocKind::Fn, .. }) = tcx
                 .associated_items(inherent_impl)
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
index e95b5142559f4..d7d4a98e63fe6 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -1272,7 +1272,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         }
 
         let candidates: Vec<_> = tcx
-            .inherent_impls(adt_did)?
+            .inherent_impls(adt_did)
             .iter()
             .filter_map(|&impl_| {
                 let (item, scope) =
diff --git a/compiler/rustc_hir_analysis/src/lib.rs b/compiler/rustc_hir_analysis/src/lib.rs
index 1dc85c4903e37..92d85d48a42c0 100644
--- a/compiler/rustc_hir_analysis/src/lib.rs
+++ b/compiler/rustc_hir_analysis/src/lib.rs
@@ -170,7 +170,7 @@ pub fn check_crate(tcx: TyCtxt<'_>) {
             let _ = tcx.ensure().coherent_trait(trait_def_id);
         }
         // these queries are executed for side-effects (error reporting):
-        let _ = tcx.ensure().crate_inherent_impls(());
+        let _ = tcx.ensure().crate_inherent_impls_validity_check(());
         let _ = tcx.ensure().crate_inherent_impls_overlap_check(());
     });
 
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index 015a728325094..b34ed4640db12 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -2126,7 +2126,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 .tcx
                 .inherent_impls(def_id)
                 .into_iter()
-                .flatten()
                 .flat_map(|i| self.tcx.associated_items(i).in_definition_order())
                 // Only assoc fn with no receivers.
                 .filter(|item| {
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 3828b40b88570..1a8afcf003d20 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -728,13 +728,13 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         let Some(simp) = simplify_type(self.tcx, self_ty, TreatParams::InstantiateWithInfer) else {
             bug!("unexpected incoherent type: {:?}", self_ty)
         };
-        for &impl_def_id in self.tcx.incoherent_impls(simp).into_iter().flatten() {
+        for &impl_def_id in self.tcx.incoherent_impls(simp).into_iter() {
             self.assemble_inherent_impl_probe(impl_def_id);
         }
     }
 
     fn assemble_inherent_impl_candidates_for_type(&mut self, def_id: DefId) {
-        let impl_def_ids = self.tcx.at(self.span).inherent_impls(def_id).into_iter().flatten();
+        let impl_def_ids = self.tcx.at(self.span).inherent_impls(def_id).into_iter();
         for &impl_def_id in impl_def_ids {
             self.assemble_inherent_impl_probe(impl_def_id);
         }
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index feb47209f5e7b..e03be4f43f73d 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -680,7 +680,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         self.tcx
                             .inherent_impls(adt_def.did())
                             .into_iter()
-                            .flatten()
                             .any(|def_id| self.associated_value(*def_id, item_name).is_some())
                     } else {
                         false
@@ -1438,7 +1437,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         .tcx
                         .inherent_impls(adt.did())
                         .into_iter()
-                        .flatten()
                         .copied()
                         .filter(|def_id| {
                             if let Some(assoc) = self.associated_value(*def_id, item_name) {
@@ -1900,7 +1898,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         call_args: Option<Vec<Ty<'tcx>>>,
     ) -> Option<Symbol> {
         if let ty::Adt(adt, adt_args) = rcvr_ty.kind() {
-            for inherent_impl_did in self.tcx.inherent_impls(adt.did()).into_iter().flatten() {
+            for inherent_impl_did in self.tcx.inherent_impls(adt.did()).into_iter() {
                 for inherent_method in
                     self.tcx.associated_items(inherent_impl_did).in_definition_order()
                 {
@@ -2114,9 +2112,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let ty::Adt(adt_def, _) = rcvr_ty.kind() else {
             return;
         };
-        // FIXME(oli-obk): try out bubbling this error up one level and cancelling the other error in that case.
-        let Ok(impls) = self.tcx.inherent_impls(adt_def.did()) else { return };
-        let mut items = impls
+        let mut items = self
+            .tcx
+            .inherent_impls(adt_def.did())
             .iter()
             .flat_map(|i| self.tcx.associated_items(i).in_definition_order())
             // Only assoc fn with no receivers and only if
@@ -2495,7 +2493,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 .and_then(|simp| {
                     tcx.incoherent_impls(simp)
                         .into_iter()
-                        .flatten()
                         .find_map(|&id| self.associated_value(id, item_name))
                 })
                 .is_some()
diff --git a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
index 53d2089296d94..69707fdbe8fa1 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
@@ -347,7 +347,7 @@ provide! { tcx, def_id, other, cdata,
         tcx.arena.alloc_from_iter(cdata.get_associated_item_or_field_def_ids(def_id.index))
     }
     associated_item => { cdata.get_associated_item(def_id.index, tcx.sess) }
-    inherent_impls => { Ok(cdata.get_inherent_implementations_for_type(tcx, def_id.index)) }
+    inherent_impls => { cdata.get_inherent_implementations_for_type(tcx, def_id.index) }
     item_attrs => { tcx.arena.alloc_from_iter(cdata.get_item_attrs(def_id.index, tcx.sess)) }
     is_mir_available => { cdata.is_item_mir_available(def_id.index) }
     is_ctfe_mir_available => { cdata.is_ctfe_mir_available(def_id.index) }
@@ -393,7 +393,7 @@ provide! { tcx, def_id, other, cdata,
     traits => { tcx.arena.alloc_from_iter(cdata.get_traits()) }
     trait_impls_in_crate => { tcx.arena.alloc_from_iter(cdata.get_trait_impls()) }
     implementations_of_trait => { cdata.get_implementations_of_trait(tcx, other) }
-    crate_incoherent_impls => { Ok(cdata.get_incoherent_impls(tcx, other)) }
+    crate_incoherent_impls => { cdata.get_incoherent_impls(tcx, other) }
 
     dep_kind => { cdata.dep_kind }
     module_children => {
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index 891f179344181..5f756672b049e 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1540,7 +1540,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             }
         }
 
-        for (def_id, impls) in &tcx.crate_inherent_impls(()).unwrap().inherent_impls {
+        for (def_id, impls) in &tcx.crate_inherent_impls(()).0.inherent_impls {
             record_defaulted_array!(self.tables.inherent_impls[def_id.to_def_id()] <- impls.iter().map(|def_id| {
                 assert!(def_id.is_local());
                 def_id.index
@@ -2089,7 +2089,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
 
         let all_impls: Vec<_> = tcx
             .crate_inherent_impls(())
-            .unwrap()
+            .0
             .incoherent_impls
             .iter()
             .map(|(&simp, impls)| IncoherentImpls {
diff --git a/compiler/rustc_middle/src/query/erase.rs b/compiler/rustc_middle/src/query/erase.rs
index bd20e6aa00537..48bf4ffced0ce 100644
--- a/compiler/rustc_middle/src/query/erase.rs
+++ b/compiler/rustc_middle/src/query/erase.rs
@@ -1,6 +1,8 @@
 use std::intrinsics::transmute_unchecked;
 use std::mem::MaybeUninit;
 
+use rustc_span::ErrorGuaranteed;
+
 use crate::query::CyclePlaceholder;
 use crate::ty::adjustment::CoerceUnsizedInfo;
 use crate::ty::{self, Ty};
@@ -216,6 +218,10 @@ impl<T0, T1> EraseType for (&'_ T0, &'_ [T1]) {
     type Result = [u8; size_of::<(&'static (), &'static [()])>()];
 }
 
+impl<T0> EraseType for (&'_ T0, Result<(), ErrorGuaranteed>) {
+    type Result = [u8; size_of::<(&'static (), Result<(), ErrorGuaranteed>)>()];
+}
+
 macro_rules! trivial {
     ($($ty:ty),+ $(,)?) => {
         $(
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 00036097ef50e..9609ef46d5c31 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -881,13 +881,13 @@ rustc_queries! {
     /// Maps a `DefId` of a type to a list of its inherent impls.
     /// Contains implementations of methods that are inherent to a type.
     /// Methods in these implementations don't need to be exported.
-    query inherent_impls(key: DefId) -> Result<&'tcx [DefId], ErrorGuaranteed> {
+    query inherent_impls(key: DefId) -> &'tcx [DefId] {
         desc { |tcx| "collecting inherent impls for `{}`", tcx.def_path_str(key) }
         cache_on_disk_if { key.is_local() }
         separate_provide_extern
     }
 
-    query incoherent_impls(key: SimplifiedType) -> Result<&'tcx [DefId], ErrorGuaranteed> {
+    query incoherent_impls(key: SimplifiedType) -> &'tcx [DefId] {
         desc { |tcx| "collecting all inherent impls for `{:?}`", key }
     }
 
@@ -1017,8 +1017,14 @@ rustc_queries! {
 
     /// Gets a complete map from all types to their inherent impls.
     /// Not meant to be used directly outside of coherence.
-    query crate_inherent_impls(k: ()) -> Result<&'tcx CrateInherentImpls, ErrorGuaranteed> {
+    query crate_inherent_impls(k: ()) -> (&'tcx CrateInherentImpls, Result<(), ErrorGuaranteed>) {
         desc { "finding all inherent impls defined in crate" }
+    }
+
+    /// Checks all types in the crate for overlap in their inherent impls. Reports errors.
+    /// Not meant to be used directly outside of coherence.
+    query crate_inherent_impls_validity_check(_: ()) -> Result<(), ErrorGuaranteed> {
+        desc { "check for inherent impls that should not be defined in crate" }
         ensure_forwards_result_if_red
     }
 
@@ -1715,7 +1721,7 @@ rustc_queries! {
     ///
     /// Do not call this directly, but instead use the `incoherent_impls` query.
     /// This query is only used to get the data necessary for that query.
-    query crate_incoherent_impls(key: (CrateNum, SimplifiedType)) -> Result<&'tcx [DefId], ErrorGuaranteed> {
+    query crate_incoherent_impls(key: (CrateNum, SimplifiedType)) -> &'tcx [DefId] {
         desc { |tcx| "collecting all impls for a type in a crate" }
         separate_provide_extern
     }
diff --git a/compiler/rustc_middle/src/ty/trait_def.rs b/compiler/rustc_middle/src/ty/trait_def.rs
index 82690f70e5f18..188107e5d5498 100644
--- a/compiler/rustc_middle/src/ty/trait_def.rs
+++ b/compiler/rustc_middle/src/ty/trait_def.rs
@@ -253,30 +253,16 @@ pub(super) fn trait_impls_of_provider(tcx: TyCtxt<'_>, trait_id: DefId) -> Trait
 }
 
 /// Query provider for `incoherent_impls`.
-pub(super) fn incoherent_impls_provider(
-    tcx: TyCtxt<'_>,
-    simp: SimplifiedType,
-) -> Result<&[DefId], ErrorGuaranteed> {
+pub(super) fn incoherent_impls_provider(tcx: TyCtxt<'_>, simp: SimplifiedType) -> &[DefId] {
     let mut impls = Vec::new();
-
-    let mut res = Ok(());
     for cnum in iter::once(LOCAL_CRATE).chain(tcx.crates(()).iter().copied()) {
-        let incoherent_impls = match tcx.crate_incoherent_impls((cnum, simp)) {
-            Ok(impls) => impls,
-            Err(e) => {
-                res = Err(e);
-                continue;
-            }
-        };
-        for &impl_def_id in incoherent_impls {
+        for &impl_def_id in tcx.crate_incoherent_impls((cnum, simp)) {
             impls.push(impl_def_id)
         }
     }
-
     debug!(?impls);
-    res?;
 
-    Ok(tcx.arena.alloc_slice(&impls))
+    tcx.arena.alloc_slice(&impls)
 }
 
 pub(super) fn traits_provider(tcx: TyCtxt<'_>, _: LocalCrate) -> &[DefId] {
diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs
index 8d137b8d8f9f1..ee6b56ca753d5 100644
--- a/compiler/rustc_monomorphize/src/collector.rs
+++ b/compiler/rustc_monomorphize/src/collector.rs
@@ -1183,7 +1183,7 @@ fn collect_alloc<'tcx>(tcx: TyCtxt<'tcx>, alloc_id: AllocId, output: &mut MonoIt
 }
 
 fn assoc_fn_of_type<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, fn_ident: Ident) -> Option<DefId> {
-    for impl_def_id in tcx.inherent_impls(def_id).ok()? {
+    for impl_def_id in tcx.inherent_impls(def_id) {
         if let Some(new) = tcx.associated_items(impl_def_id).find_by_name_and_kind(
             tcx,
             fn_ident,
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index 7ea057c7b4bcb..35d166e8b4ab3 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -1825,10 +1825,12 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
             // Doing analysis on local `DefId`s would cause infinite recursion.
             return;
         }
-        let Ok(impls) = self.r.tcx.inherent_impls(def_id) else { return };
         // Look at all the associated functions without receivers in the type's
         // inherent impls to look for builders that return `Self`
-        let mut items = impls
+        let mut items = self
+            .r
+            .tcx
+            .inherent_impls(def_id)
             .iter()
             .flat_map(|i| self.r.tcx.associated_items(i).in_definition_order())
             // Only assoc fn with no receivers.
diff --git a/tests/ui/const-generics/wrong-normalization.rs b/tests/ui/const-generics/wrong-normalization.rs
index 8b2323e3d479c..f1ce317b3f78b 100644
--- a/tests/ui/const-generics/wrong-normalization.rs
+++ b/tests/ui/const-generics/wrong-normalization.rs
@@ -15,6 +15,5 @@ pub struct I8<const F: i8>;
 
 impl <I8<{i8::MIN}> as Identity>::Identity {
 //~^ ERROR no nominal type found for inherent implementation
-//~| ERROR no associated item named `MIN` found for type `i8`
     pub fn foo(&self) {}
 }
diff --git a/tests/ui/const-generics/wrong-normalization.stderr b/tests/ui/const-generics/wrong-normalization.stderr
index 379a5593dd640..2f8dfc895b279 100644
--- a/tests/ui/const-generics/wrong-normalization.stderr
+++ b/tests/ui/const-generics/wrong-normalization.stderr
@@ -6,18 +6,6 @@ LL | impl <I8<{i8::MIN}> as Identity>::Identity {
    |
    = note: either implement a trait on it or create a newtype to wrap it instead
 
-error[E0599]: no associated item named `MIN` found for type `i8` in the current scope
-  --> $DIR/wrong-normalization.rs:16:15
-   |
-LL | impl <I8<{i8::MIN}> as Identity>::Identity {
-   |               ^^^ associated item not found in `i8`
-   |
-help: you are looking for the module in `std`, not the primitive type
-   |
-LL | impl <I8<{std::i8::MIN}> as Identity>::Identity {
-   |           +++++
-
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
-Some errors have detailed explanations: E0118, E0599.
-For more information about an error, try `rustc --explain E0118`.
+For more information about this error, try `rustc --explain E0118`.
diff --git a/tests/ui/impl-trait/where-allowed.rs b/tests/ui/impl-trait/where-allowed.rs
index 72ce617693e40..3f435f0f443b4 100644
--- a/tests/ui/impl-trait/where-allowed.rs
+++ b/tests/ui/impl-trait/where-allowed.rs
@@ -42,7 +42,7 @@ fn in_dyn_Fn_return_in_parameters(_: &dyn Fn() -> impl Debug) { panic!() }
 fn in_dyn_Fn_parameter_in_return() -> &'static dyn Fn(impl Debug) { panic!() }
 //~^ ERROR `impl Trait` is not allowed in the parameters of `Fn` trait bounds
 
-// Allowed
+// Allowed (but it's still ambiguous; nothing constrains the RPIT in this body).
 fn in_dyn_Fn_return_in_return() -> &'static dyn Fn() -> impl Debug { panic!() }
 //~^ ERROR: type annotations needed
 
@@ -79,7 +79,6 @@ fn in_impl_Trait_in_parameters(_: impl Iterator<Item = impl Iterator>) { panic!(
 // Allowed
 fn in_impl_Trait_in_return() -> impl IntoIterator<Item = impl IntoIterator> {
     vec![vec![0; 10], vec![12; 7], vec![8; 3]]
-    //~^ ERROR: no function or associated item named `into_vec` found for slice `[_]`
 }
 
 // Disallowed
diff --git a/tests/ui/impl-trait/where-allowed.stderr b/tests/ui/impl-trait/where-allowed.stderr
index 1fb69db98c162..2770a6cc40e59 100644
--- a/tests/ui/impl-trait/where-allowed.stderr
+++ b/tests/ui/impl-trait/where-allowed.stderr
@@ -17,7 +17,7 @@ LL | fn in_impl_Fn_parameter_in_return() -> &'static impl Fn(impl Debug) { panic
    |                                                 outer `impl Trait`
 
 error[E0658]: `impl Trait` in associated types is unstable
-  --> $DIR/where-allowed.rs:122:16
+  --> $DIR/where-allowed.rs:121:16
    |
 LL |     type Out = impl Debug;
    |                ^^^^^^^^^^
@@ -27,7 +27,7 @@ LL |     type Out = impl Debug;
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0658]: `impl Trait` in type aliases is unstable
-  --> $DIR/where-allowed.rs:159:23
+  --> $DIR/where-allowed.rs:158:23
    |
 LL | type InTypeAlias<R> = impl Debug;
    |                       ^^^^^^^^^^
@@ -37,7 +37,7 @@ LL | type InTypeAlias<R> = impl Debug;
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0658]: `impl Trait` in type aliases is unstable
-  --> $DIR/where-allowed.rs:162:39
+  --> $DIR/where-allowed.rs:161:39
    |
 LL | type InReturnInTypeAlias<R> = fn() -> impl Debug;
    |                                       ^^^^^^^^^^
@@ -143,7 +143,7 @@ LL | fn in_Fn_return_in_generics<F: Fn() -> impl Debug> (_: F) { panic!() }
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in field types
-  --> $DIR/where-allowed.rs:86:32
+  --> $DIR/where-allowed.rs:85:32
    |
 LL | struct InBraceStructField { x: impl Debug }
    |                                ^^^^^^^^^^
@@ -151,7 +151,7 @@ LL | struct InBraceStructField { x: impl Debug }
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in field types
-  --> $DIR/where-allowed.rs:90:41
+  --> $DIR/where-allowed.rs:89:41
    |
 LL | struct InAdtInBraceStructField { x: Vec<impl Debug> }
    |                                         ^^^^^^^^^^
@@ -159,7 +159,7 @@ LL | struct InAdtInBraceStructField { x: Vec<impl Debug> }
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in field types
-  --> $DIR/where-allowed.rs:94:27
+  --> $DIR/where-allowed.rs:93:27
    |
 LL | struct InTupleStructField(impl Debug);
    |                           ^^^^^^^^^^
@@ -167,7 +167,7 @@ LL | struct InTupleStructField(impl Debug);
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in field types
-  --> $DIR/where-allowed.rs:99:25
+  --> $DIR/where-allowed.rs:98:25
    |
 LL |     InBraceVariant { x: impl Debug },
    |                         ^^^^^^^^^^
@@ -175,7 +175,7 @@ LL |     InBraceVariant { x: impl Debug },
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in field types
-  --> $DIR/where-allowed.rs:101:20
+  --> $DIR/where-allowed.rs:100:20
    |
 LL |     InTupleVariant(impl Debug),
    |                    ^^^^^^^^^^
@@ -183,7 +183,7 @@ LL |     InTupleVariant(impl Debug),
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in `extern fn` parameters
-  --> $DIR/where-allowed.rs:143:33
+  --> $DIR/where-allowed.rs:142:33
    |
 LL |     fn in_foreign_parameters(_: impl Debug);
    |                                 ^^^^^^^^^^
@@ -191,7 +191,7 @@ LL |     fn in_foreign_parameters(_: impl Debug);
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in `extern fn` return types
-  --> $DIR/where-allowed.rs:146:31
+  --> $DIR/where-allowed.rs:145:31
    |
 LL |     fn in_foreign_return() -> impl Debug;
    |                               ^^^^^^^^^^
@@ -199,7 +199,7 @@ LL |     fn in_foreign_return() -> impl Debug;
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in `fn` pointer return types
-  --> $DIR/where-allowed.rs:162:39
+  --> $DIR/where-allowed.rs:161:39
    |
 LL | type InReturnInTypeAlias<R> = fn() -> impl Debug;
    |                                       ^^^^^^^^^^
@@ -207,7 +207,7 @@ LL | type InReturnInTypeAlias<R> = fn() -> impl Debug;
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in traits
-  --> $DIR/where-allowed.rs:167:16
+  --> $DIR/where-allowed.rs:166:16
    |
 LL | impl PartialEq<impl Debug> for () {
    |                ^^^^^^^^^^
@@ -215,7 +215,7 @@ LL | impl PartialEq<impl Debug> for () {
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in impl headers
-  --> $DIR/where-allowed.rs:172:24
+  --> $DIR/where-allowed.rs:171:24
    |
 LL | impl PartialEq<()> for impl Debug {
    |                        ^^^^^^^^^^
@@ -223,7 +223,7 @@ LL | impl PartialEq<()> for impl Debug {
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in impl headers
-  --> $DIR/where-allowed.rs:177:6
+  --> $DIR/where-allowed.rs:176:6
    |
 LL | impl impl Debug {
    |      ^^^^^^^^^^
@@ -231,7 +231,7 @@ LL | impl impl Debug {
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in impl headers
-  --> $DIR/where-allowed.rs:183:24
+  --> $DIR/where-allowed.rs:182:24
    |
 LL | impl InInherentImplAdt<impl Debug> {
    |                        ^^^^^^^^^^
@@ -239,7 +239,7 @@ LL | impl InInherentImplAdt<impl Debug> {
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in bounds
-  --> $DIR/where-allowed.rs:189:11
+  --> $DIR/where-allowed.rs:188:11
    |
 LL |     where impl Debug: Debug
    |           ^^^^^^^^^^
@@ -247,7 +247,7 @@ LL |     where impl Debug: Debug
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in bounds
-  --> $DIR/where-allowed.rs:196:15
+  --> $DIR/where-allowed.rs:195:15
    |
 LL |     where Vec<impl Debug>: Debug
    |               ^^^^^^^^^^
@@ -255,7 +255,7 @@ LL |     where Vec<impl Debug>: Debug
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in bounds
-  --> $DIR/where-allowed.rs:203:24
+  --> $DIR/where-allowed.rs:202:24
    |
 LL |     where T: PartialEq<impl Debug>
    |                        ^^^^^^^^^^
@@ -263,7 +263,7 @@ LL |     where T: PartialEq<impl Debug>
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in the parameters of `Fn` trait bounds
-  --> $DIR/where-allowed.rs:210:17
+  --> $DIR/where-allowed.rs:209:17
    |
 LL |     where T: Fn(impl Debug)
    |                 ^^^^^^^^^^
@@ -271,7 +271,7 @@ LL |     where T: Fn(impl Debug)
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in the return type of `Fn` trait bounds
-  --> $DIR/where-allowed.rs:217:22
+  --> $DIR/where-allowed.rs:216:22
    |
 LL |     where T: Fn() -> impl Debug
    |                      ^^^^^^^^^^
@@ -279,7 +279,7 @@ LL |     where T: Fn() -> impl Debug
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in generic parameter defaults
-  --> $DIR/where-allowed.rs:223:40
+  --> $DIR/where-allowed.rs:222:40
    |
 LL | struct InStructGenericParamDefault<T = impl Debug>(T);
    |                                        ^^^^^^^^^^
@@ -287,7 +287,7 @@ LL | struct InStructGenericParamDefault<T = impl Debug>(T);
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in generic parameter defaults
-  --> $DIR/where-allowed.rs:227:36
+  --> $DIR/where-allowed.rs:226:36
    |
 LL | enum InEnumGenericParamDefault<T = impl Debug> { Variant(T) }
    |                                    ^^^^^^^^^^
@@ -295,7 +295,7 @@ LL | enum InEnumGenericParamDefault<T = impl Debug> { Variant(T) }
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in generic parameter defaults
-  --> $DIR/where-allowed.rs:231:38
+  --> $DIR/where-allowed.rs:230:38
    |
 LL | trait InTraitGenericParamDefault<T = impl Debug> {}
    |                                      ^^^^^^^^^^
@@ -303,7 +303,7 @@ LL | trait InTraitGenericParamDefault<T = impl Debug> {}
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in generic parameter defaults
-  --> $DIR/where-allowed.rs:235:41
+  --> $DIR/where-allowed.rs:234:41
    |
 LL | type InTypeAliasGenericParamDefault<T = impl Debug> = T;
    |                                         ^^^^^^^^^^
@@ -311,7 +311,7 @@ LL | type InTypeAliasGenericParamDefault<T = impl Debug> = T;
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in generic parameter defaults
-  --> $DIR/where-allowed.rs:239:11
+  --> $DIR/where-allowed.rs:238:11
    |
 LL | impl <T = impl Debug> T {}
    |           ^^^^^^^^^^
@@ -319,7 +319,7 @@ LL | impl <T = impl Debug> T {}
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in generic parameter defaults
-  --> $DIR/where-allowed.rs:246:40
+  --> $DIR/where-allowed.rs:245:40
    |
 LL | fn in_method_generic_param_default<T = impl Debug>(_: T) {}
    |                                        ^^^^^^^^^^
@@ -327,7 +327,7 @@ LL | fn in_method_generic_param_default<T = impl Debug>(_: T) {}
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in the type of variable bindings
-  --> $DIR/where-allowed.rs:252:29
+  --> $DIR/where-allowed.rs:251:29
    |
 LL |     let _in_local_variable: impl Fn() = || {};
    |                             ^^^^^^^^^
@@ -335,7 +335,7 @@ LL |     let _in_local_variable: impl Fn() = || {};
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0562]: `impl Trait` is not allowed in closure return types
-  --> $DIR/where-allowed.rs:254:46
+  --> $DIR/where-allowed.rs:253:46
    |
 LL |     let _in_return_in_local_variable = || -> impl Fn() { || {} };
    |                                              ^^^^^^^^^
@@ -363,7 +363,7 @@ LL | fn in_impl_Fn_return_in_return() -> &'static impl Fn() -> impl Debug { pani
              where Args: Tuple, F: Fn<Args>, A: Allocator, F: ?Sized;
 
 error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
-  --> $DIR/where-allowed.rs:239:7
+  --> $DIR/where-allowed.rs:238:7
    |
 LL | impl <T = impl Debug> T {}
    |       ^^^^^^^^^^^^^^
@@ -373,25 +373,15 @@ LL | impl <T = impl Debug> T {}
    = note: `#[deny(invalid_type_param_default)]` on by default
 
 error[E0118]: no nominal type found for inherent implementation
-  --> $DIR/where-allowed.rs:239:1
+  --> $DIR/where-allowed.rs:238:1
    |
 LL | impl <T = impl Debug> T {}
    | ^^^^^^^^^^^^^^^^^^^^^^^ impl requires a nominal type
    |
    = note: either implement a trait on it or create a newtype to wrap it instead
 
-error[E0599]: no function or associated item named `into_vec` found for slice `[_]` in the current scope
-  --> $DIR/where-allowed.rs:81:5
-   |
-LL |     vec![vec![0; 10], vec![12; 7], vec![8; 3]]
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ function or associated item not found in `[_]`
-   |
-help: there is an associated function `to_vec` with a similar name
-  --> $SRC_DIR/alloc/src/slice.rs:LL:COL
-   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
-
 error[E0053]: method `in_trait_impl_return` has an incompatible type for trait
-  --> $DIR/where-allowed.rs:129:34
+  --> $DIR/where-allowed.rs:128:34
    |
 LL |     type Out = impl Debug;
    |                ---------- the expected opaque type
@@ -400,7 +390,7 @@ LL |     fn in_trait_impl_return() -> impl Debug { () }
    |                                  ^^^^^^^^^^ expected opaque type, found a different opaque type
    |
 note: type in trait
-  --> $DIR/where-allowed.rs:119:34
+  --> $DIR/where-allowed.rs:118:34
    |
 LL |     fn in_trait_impl_return() -> Self::Out;
    |                                  ^^^^^^^^^
@@ -413,7 +403,7 @@ LL |     fn in_trait_impl_return() -> <() as DummyTrait>::Out { () }
    |                                  ~~~~~~~~~~~~~~~~~~~~~~~
 
 error: unconstrained opaque type
-  --> $DIR/where-allowed.rs:122:16
+  --> $DIR/where-allowed.rs:121:16
    |
 LL |     type Out = impl Debug;
    |                ^^^^^^^^^^
@@ -421,7 +411,7 @@ LL |     type Out = impl Debug;
    = note: `Out` must be used in combination with a concrete type within the same impl
 
 error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
-  --> $DIR/where-allowed.rs:246:36
+  --> $DIR/where-allowed.rs:245:36
    |
 LL | fn in_method_generic_param_default<T = impl Debug>(_: T) {}
    |                                    ^^^^^^^^^^^^^^
@@ -429,13 +419,13 @@ LL | fn in_method_generic_param_default<T = impl Debug>(_: T) {}
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
 
-error: aborting due to 50 previous errors
+error: aborting due to 49 previous errors
 
-Some errors have detailed explanations: E0053, E0118, E0283, E0562, E0599, E0658, E0666.
+Some errors have detailed explanations: E0053, E0118, E0283, E0562, E0658, E0666.
 For more information about an error, try `rustc --explain E0053`.
 Future incompatibility report: Future breakage diagnostic:
 error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
-  --> $DIR/where-allowed.rs:239:7
+  --> $DIR/where-allowed.rs:238:7
    |
 LL | impl <T = impl Debug> T {}
    |       ^^^^^^^^^^^^^^
@@ -446,7 +436,7 @@ LL | impl <T = impl Debug> T {}
 
 Future breakage diagnostic:
 error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
-  --> $DIR/where-allowed.rs:246:36
+  --> $DIR/where-allowed.rs:245:36
    |
 LL | fn in_method_generic_param_default<T = impl Debug>(_: T) {}
    |                                    ^^^^^^^^^^^^^^
diff --git a/tests/ui/traits/incoherent-impl-ambiguity.rs b/tests/ui/traits/incoherent-impl-ambiguity.rs
new file mode 100644
index 0000000000000..b5fed95e11c44
--- /dev/null
+++ b/tests/ui/traits/incoherent-impl-ambiguity.rs
@@ -0,0 +1,14 @@
+// Make sure that an invalid inherent impl doesn't totally clobber all of the
+// other inherent impls, which lead to mysterious method/assoc-item probing errors.
+
+impl () {}
+//~^ ERROR cannot define inherent `impl` for primitive types
+
+struct W;
+impl W {
+    const CONST: u32 = 0;
+}
+
+fn main() {
+    let _ = W::CONST;
+}
diff --git a/tests/ui/traits/incoherent-impl-ambiguity.stderr b/tests/ui/traits/incoherent-impl-ambiguity.stderr
new file mode 100644
index 0000000000000..9c050a7295581
--- /dev/null
+++ b/tests/ui/traits/incoherent-impl-ambiguity.stderr
@@ -0,0 +1,11 @@
+error[E0390]: cannot define inherent `impl` for primitive types
+  --> $DIR/incoherent-impl-ambiguity.rs:4:1
+   |
+LL | impl () {}
+   | ^^^^^^^
+   |
+   = help: consider using an extension trait instead
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0390`.

From 28f69805de661551d3bba35bd2c6df96777e2df2 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Tue, 24 Sep 2024 10:11:23 -0400
Subject: [PATCH 03/14] Fix tools

---
 src/librustdoc/clean/inline.rs                           | 4 ++--
 src/librustdoc/clean/types.rs                            | 4 ++--
 src/librustdoc/passes/collect_intra_doc_links.rs         | 1 -
 src/tools/clippy/clippy_lints/src/derive.rs              | 1 -
 src/tools/clippy/clippy_lints/src/inherent_impl.rs       | 4 +---
 src/tools/clippy/clippy_lints/src/len_zero.rs            | 3 +--
 src/tools/clippy/clippy_lints/src/methods/or_fun_call.rs | 1 -
 src/tools/clippy/clippy_utils/src/lib.rs                 | 8 ++------
 src/tools/clippy/clippy_utils/src/ty.rs                  | 2 +-
 9 files changed, 9 insertions(+), 19 deletions(-)

diff --git a/src/librustdoc/clean/inline.rs b/src/librustdoc/clean/inline.rs
index 701bf61809673..b7d6b3dda72b4 100644
--- a/src/librustdoc/clean/inline.rs
+++ b/src/librustdoc/clean/inline.rs
@@ -373,7 +373,7 @@ pub(crate) fn build_impls(
     let tcx = cx.tcx;
 
     // for each implementation of an item represented by `did`, build the clean::Item for that impl
-    for &did in tcx.inherent_impls(did).into_iter().flatten() {
+    for &did in tcx.inherent_impls(did).into_iter() {
         cx.with_param_env(did, |cx| {
             build_impl(cx, did, attrs, ret);
         });
@@ -388,7 +388,7 @@ pub(crate) fn build_impls(
     if tcx.has_attr(did, sym::rustc_has_incoherent_inherent_impls) {
         let type_ =
             if tcx.is_trait(did) { SimplifiedType::Trait(did) } else { SimplifiedType::Adt(did) };
-        for &did in tcx.incoherent_impls(type_).into_iter().flatten() {
+        for &did in tcx.incoherent_impls(type_).into_iter() {
             cx.with_param_env(did, |cx| {
                 build_impl(cx, did, attrs, ret);
             });
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index 31710bc014af4..986406c1e403a 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -1863,7 +1863,7 @@ impl PrimitiveType {
             .get(self)
             .into_iter()
             .flatten()
-            .flat_map(move |&simp| tcx.incoherent_impls(simp).into_iter().flatten())
+            .flat_map(move |&simp| tcx.incoherent_impls(simp).into_iter())
             .copied()
     }
 
@@ -1871,7 +1871,7 @@ impl PrimitiveType {
         Self::simplified_types()
             .values()
             .flatten()
-            .flat_map(move |&simp| tcx.incoherent_impls(simp).into_iter().flatten())
+            .flat_map(move |&simp| tcx.incoherent_impls(simp).into_iter())
             .copied()
     }
 
diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
index ddc80ea7cb128..29342dcac592b 100644
--- a/src/librustdoc/passes/collect_intra_doc_links.rs
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -608,7 +608,6 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
                 let mut assoc_items: Vec<_> = tcx
                     .inherent_impls(did)
                     .into_iter()
-                    .flatten()
                     .flat_map(|&imp| {
                         filter_assoc_items_by_name_and_namespace(
                             tcx,
diff --git a/src/tools/clippy/clippy_lints/src/derive.rs b/src/tools/clippy/clippy_lints/src/derive.rs
index 636698e96f6d1..649c480fb92a1 100644
--- a/src/tools/clippy/clippy_lints/src/derive.rs
+++ b/src/tools/clippy/clippy_lints/src/derive.rs
@@ -386,7 +386,6 @@ fn check_unsafe_derive_deserialize<'tcx>(
             .tcx
             .inherent_impls(def.did())
             .into_iter()
-            .flatten()
             .map(|imp_did| cx.tcx.hir().expect_item(imp_did.expect_local()))
             .any(|imp| has_unsafe(cx, imp))
     {
diff --git a/src/tools/clippy/clippy_lints/src/inherent_impl.rs b/src/tools/clippy/clippy_lints/src/inherent_impl.rs
index d39f910f9936d..309d2dfb28b87 100644
--- a/src/tools/clippy/clippy_lints/src/inherent_impl.rs
+++ b/src/tools/clippy/clippy_lints/src/inherent_impl.rs
@@ -51,9 +51,7 @@ impl<'tcx> LateLintPass<'tcx> for MultipleInherentImpl {
         // List of spans to lint. (lint_span, first_span)
         let mut lint_spans = Vec::new();
 
-        let Ok(impls) = cx.tcx.crate_inherent_impls(()) else {
-            return;
-        };
+        let (impls, _) = cx.tcx.crate_inherent_impls(());
 
         for (&id, impl_ids) in &impls.inherent_impls {
             if impl_ids.len() < 2
diff --git a/src/tools/clippy/clippy_lints/src/len_zero.rs b/src/tools/clippy/clippy_lints/src/len_zero.rs
index 0bc7fc2dd9d1e..16f86b18e2e55 100644
--- a/src/tools/clippy/clippy_lints/src/len_zero.rs
+++ b/src/tools/clippy/clippy_lints/src/len_zero.rs
@@ -448,7 +448,6 @@ fn check_for_is_empty(
         .tcx
         .inherent_impls(impl_ty)
         .into_iter()
-        .flatten()
         .flat_map(|&id| cx.tcx.associated_items(id).filter_by_name_unhygienic(is_empty))
         .find(|item| item.kind == AssocKind::Fn);
 
@@ -616,7 +615,7 @@ fn has_is_empty(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
     /// Checks the inherent impl's items for an `is_empty(self)` method.
     fn has_is_empty_impl(cx: &LateContext<'_>, id: DefId) -> bool {
         let is_empty = sym!(is_empty);
-        cx.tcx.inherent_impls(id).into_iter().flatten().any(|imp| {
+        cx.tcx.inherent_impls(id).into_iter().any(|imp| {
             cx.tcx
                 .associated_items(*imp)
                 .filter_by_name_unhygienic(is_empty)
diff --git a/src/tools/clippy/clippy_lints/src/methods/or_fun_call.rs b/src/tools/clippy/clippy_lints/src/methods/or_fun_call.rs
index e4326cb958e5f..af71799f0a731 100644
--- a/src/tools/clippy/clippy_lints/src/methods/or_fun_call.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/or_fun_call.rs
@@ -78,7 +78,6 @@ pub(super) fn check<'tcx>(
             cx.tcx
                 .inherent_impls(adt_def.did())
                 .into_iter()
-                .flatten()
                 .flat_map(|impl_id| cx.tcx.associated_items(impl_id).filter_by_name_unhygienic(sugg))
                 .find_map(|assoc| {
                     if assoc.fn_has_self_parameter
diff --git a/src/tools/clippy/clippy_utils/src/lib.rs b/src/tools/clippy/clippy_utils/src/lib.rs
index 0d0d6219c5e05..aed0bc565d8e9 100644
--- a/src/tools/clippy/clippy_utils/src/lib.rs
+++ b/src/tools/clippy/clippy_utils/src/lib.rs
@@ -589,14 +589,11 @@ fn find_primitive_impls<'tcx>(tcx: TyCtxt<'tcx>, name: &str) -> impl Iterator<It
         "f32" => SimplifiedType::Float(FloatTy::F32),
         "f64" => SimplifiedType::Float(FloatTy::F64),
         _ => {
-            return Result::<&[_], rustc_errors::ErrorGuaranteed>::Ok(&[])
-                .into_iter()
-                .flatten()
-                .copied();
+            return [].iter().copied();
         },
     };
 
-    tcx.incoherent_impls(ty).into_iter().flatten().copied()
+    tcx.incoherent_impls(ty).into_iter().copied()
 }
 
 fn non_local_item_children_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: Symbol) -> Vec<Res> {
@@ -721,7 +718,6 @@ pub fn def_path_res(tcx: TyCtxt<'_>, path: &[&str]) -> Vec<Res> {
                 let inherent_impl_children = tcx
                     .inherent_impls(def_id)
                     .into_iter()
-                    .flatten()
                     .flat_map(|&impl_def_id| item_children_by_name(tcx, impl_def_id, segment));
 
                 let direct_children = item_children_by_name(tcx, def_id, segment);
diff --git a/src/tools/clippy/clippy_utils/src/ty.rs b/src/tools/clippy/clippy_utils/src/ty.rs
index 585134209ca3a..22aaaa1b73419 100644
--- a/src/tools/clippy/clippy_utils/src/ty.rs
+++ b/src/tools/clippy/clippy_utils/src/ty.rs
@@ -1316,7 +1316,7 @@ pub fn deref_chain<'cx, 'tcx>(cx: &'cx LateContext<'tcx>, ty: Ty<'tcx>) -> impl
 /// If you need this, you should wrap this call in `clippy_utils::ty::deref_chain().any(...)`.
 pub fn get_adt_inherent_method<'a>(cx: &'a LateContext<'_>, ty: Ty<'_>, method_name: Symbol) -> Option<&'a AssocItem> {
     if let Some(ty_did) = ty.ty_adt_def().map(AdtDef::did) {
-        cx.tcx.inherent_impls(ty_did).into_iter().flatten().find_map(|&did| {
+        cx.tcx.inherent_impls(ty_did).into_iter().find_map(|&did| {
             cx.tcx
                 .associated_items(did)
                 .filter_by_name_unhygienic(method_name)

From e95d15a11519f0fe3d83f39feb71625a81be4249 Mon Sep 17 00:00:00 2001
From: Trevor Gross <tmgross@umich.edu>
Date: Mon, 26 Aug 2024 14:56:18 -0400
Subject: [PATCH 04/14] Pin memchr to 2.5.0 in the library rather than
 rustc_ast

The latest versions of `memchr` experience LTO-related issues when
compiling for windows-gnu [1], so needs to be pinned. The issue is
present in the standard library.

`memchr` has been pinned in `rustc_ast`, but since the workspace was
recently split, this pin no longer has any effect on library crates.

Resolve this by adding `memchr` as an _unused_ dependency in `std`,
pinned to 2.5. Additionally, remove the pin in `rustc_ast` to allow
non-library crates to upgrade to the latest version.

Link: https://github.com/rust-lang/rust/issues/127890 [1]
---
 Cargo.lock                    | 4 ++--
 compiler/rustc_ast/Cargo.toml | 3 +--
 library/Cargo.lock            | 1 +
 library/std/Cargo.toml        | 4 ++++
 4 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index e973d7f9a2ae0..47ad7ab3e9814 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2177,9 +2177,9 @@ dependencies = [
 
 [[package]]
 name = "memchr"
-version = "2.5.0"
+version = "2.7.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
+checksum = "78ca9ab1a0babb1e7d5695e3530886289c18cf2f87ec19a575a0abdce112e3a3"
 
 [[package]]
 name = "memmap2"
diff --git a/compiler/rustc_ast/Cargo.toml b/compiler/rustc_ast/Cargo.toml
index d33f9666b484c..34c612dac692b 100644
--- a/compiler/rustc_ast/Cargo.toml
+++ b/compiler/rustc_ast/Cargo.toml
@@ -4,10 +4,9 @@ version = "0.0.0"
 edition = "2021"
 
 [dependencies]
-# FIXME: bumping memchr to 2.7.1 causes linker errors in MSVC thin-lto
 # tidy-alphabetical-start
 bitflags = "2.4.1"
-memchr = "=2.5.0"
+memchr = "2.7.4"
 rustc_ast_ir = { path = "../rustc_ast_ir" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_index = { path = "../rustc_index" }
diff --git a/library/Cargo.lock b/library/Cargo.lock
index ded30dd82f7b4..2343b2baf8347 100644
--- a/library/Cargo.lock
+++ b/library/Cargo.lock
@@ -326,6 +326,7 @@ dependencies = [
  "hashbrown",
  "hermit-abi",
  "libc",
+ "memchr",
  "miniz_oxide",
  "object",
  "panic_abort",
diff --git a/library/std/Cargo.toml b/library/std/Cargo.toml
index 9a31fd21dc71a..ea11586f9a519 100644
--- a/library/std/Cargo.toml
+++ b/library/std/Cargo.toml
@@ -23,6 +23,10 @@ unwind = { path = "../unwind" }
 hashbrown = { version = "0.14", default-features = false, features = [
     'rustc-dep-of-std',
 ] }
+# FIXME(#127890): `object` depends on `memchr`, but `memchr` > v2.5 causes
+# issues with LTO. This dependency is not used directly, but pin it here so
+# it resolves to 2.5. To be removed once rust-lang/rust#127890 is fixed.
+memchr = { version = "=2.5.0", default-features = false, features = ["rustc-dep-of-std"] }
 std_detect = { path = "../stdarch/crates/std_detect", default-features = false, features = [
     'rustc-dep-of-std',
 ] }

From 50729fe6ca20721c81bea279512124507256ee89 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E8=AE=B8=E6=9D=B0=E5=8F=8B=20Jieyou=20Xu=20=28Joe=29?=
 <jieyouxu@outlook.com>
Date: Tue, 24 Sep 2024 17:02:47 +0000
Subject: [PATCH 05/14] Mention `COMPILETEST_VERBOSE_CRASHES` on crash test
 failure

---
 src/tools/compiletest/src/runtest/crash.rs | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/tools/compiletest/src/runtest/crash.rs b/src/tools/compiletest/src/runtest/crash.rs
index 7f2bec4949be7..885ed3b08faca 100644
--- a/src/tools/compiletest/src/runtest/crash.rs
+++ b/src/tools/compiletest/src/runtest/crash.rs
@@ -15,10 +15,11 @@ impl TestCx<'_> {
         // if a test does not crash, consider it an error
         if proc_res.status.success() || matches!(proc_res.status.code(), Some(1 | 0)) {
             self.fatal(&format!(
-                "crashtest no longer crashes/triggers ICE, horray! Please give it a meaningful name, \
-            add a doc-comment to the start of the test explaining why it exists and \
-            move it to tests/ui or wherever you see fit. Adding 'Fixes #<issueNr>' to your PR description \
-            ensures that the corresponding ticket is auto-closed upon merge."
+                "crashtest no longer crashes/triggers ICE, horray! Please give it a meaningful \
+                name, add a doc-comment to the start of the test explaining why it exists and \
+                move it to tests/ui or wherever you see fit. Adding 'Fixes #<issueNr>' to your PR \
+                description ensures that the corresponding ticket is auto-closed upon merge. \
+                If you want to see verbose output, set `COMPILETEST_VERBOSE_CRASHES=1`."
             ));
         }
     }

From 46fd76e9a5687dc7ac6bfad1c715ceaef9e8cf29 Mon Sep 17 00:00:00 2001
From: Aviram Hassan <aviramyhassan@gmail.com>
Date: Tue, 24 Sep 2024 18:52:54 +0300
Subject: [PATCH 06/14] add InProgress ErrorKind gated behind
 io_error_inprogress feature

Co-authored-by: David Tolnay <dtolnay@gmail.com>
Co-authored-by: nora <48135649+Noratrieb@users.noreply.github.com>
---
 library/std/src/io/error.rs                | 6 ++++++
 library/std/src/io/error/repr_bitpacked.rs | 1 +
 library/std/src/sys/pal/unix/mod.rs        | 1 +
 3 files changed, 8 insertions(+)

diff --git a/library/std/src/io/error.rs b/library/std/src/io/error.rs
index 6ecd9469c1740..795cc64e957da 100644
--- a/library/std/src/io/error.rs
+++ b/library/std/src/io/error.rs
@@ -400,6 +400,11 @@ pub enum ErrorKind {
     #[stable(feature = "out_of_memory_error", since = "1.54.0")]
     OutOfMemory,
 
+    /// The operation was partially successful and needs to be checked
+    /// later on due to not blocking.
+    #[unstable(feature = "io_error_inprogress", issue = "none")]
+    InProgress,
+
     // "Unusual" error kinds which do not correspond simply to (sets
     // of) OS error codes, should be added just above this comment.
     // `Other` and `Uncategorized` should remain at the end:
@@ -449,6 +454,7 @@ impl ErrorKind {
             FilesystemQuotaExceeded => "filesystem quota exceeded",
             HostUnreachable => "host unreachable",
             Interrupted => "operation interrupted",
+            InProgress => "in progress",
             InvalidData => "invalid data",
             InvalidFilename => "invalid filename",
             InvalidInput => "invalid input parameter",
diff --git a/library/std/src/io/error/repr_bitpacked.rs b/library/std/src/io/error/repr_bitpacked.rs
index 9d3ade46bd929..80ba8455df347 100644
--- a/library/std/src/io/error/repr_bitpacked.rs
+++ b/library/std/src/io/error/repr_bitpacked.rs
@@ -348,6 +348,7 @@ fn kind_from_prim(ek: u32) -> Option<ErrorKind> {
         UnexpectedEof,
         Unsupported,
         OutOfMemory,
+        InProgress,
         Uncategorized,
     })
 }
diff --git a/library/std/src/sys/pal/unix/mod.rs b/library/std/src/sys/pal/unix/mod.rs
index 1c9159e5fba86..0d63b1119d59a 100644
--- a/library/std/src/sys/pal/unix/mod.rs
+++ b/library/std/src/sys/pal/unix/mod.rs
@@ -279,6 +279,7 @@ pub fn decode_error_kind(errno: i32) -> ErrorKind {
         libc::ETIMEDOUT => TimedOut,
         libc::ETXTBSY => ExecutableFileBusy,
         libc::EXDEV => CrossesDevices,
+        libc::EINPROGRESS => InProgress,
 
         libc::EACCES | libc::EPERM => PermissionDenied,
 

From 2fdeb3b8f4cb91eb545880cc0b5db003ef4869b7 Mon Sep 17 00:00:00 2001
From: Lukas Markeffsky <@>
Date: Tue, 24 Sep 2024 20:17:52 +0200
Subject: [PATCH 07/14] rustdoc: inherit parent's stability where applicable

---
 compiler/rustc_attr/src/builtin.rs |  2 +-
 src/librustdoc/clean/types.rs      | 40 +++++++++++++++++++++++++++++-
 tests/rustdoc/const-display.rs     | 18 +++++++++-----
 tests/rustdoc/stability.rs         | 31 ++++++++++++++++++++++-
 4 files changed, 82 insertions(+), 9 deletions(-)

diff --git a/compiler/rustc_attr/src/builtin.rs b/compiler/rustc_attr/src/builtin.rs
index dcc4cf2478f33..762ebc47ca9d0 100644
--- a/compiler/rustc_attr/src/builtin.rs
+++ b/compiler/rustc_attr/src/builtin.rs
@@ -153,7 +153,7 @@ pub enum StabilityLevel {
 }
 
 /// Rust release in which a feature is stabilized.
-#[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
+#[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, PartialOrd, Ord, Hash)]
 #[derive(HashStable_Generic)]
 pub enum StableSince {
     Version(RustcVersion),
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index 31710bc014af4..a0f44d152b246 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -384,7 +384,45 @@ fn is_field_vis_inherited(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
 
 impl Item {
     pub(crate) fn stability(&self, tcx: TyCtxt<'_>) -> Option<Stability> {
-        self.def_id().and_then(|did| tcx.lookup_stability(did))
+        let (mut def_id, mut stability) = if let Some(inlined) = self.inline_stmt_id {
+            let inlined_def_id = inlined.to_def_id();
+            if let Some(stability) = tcx.lookup_stability(inlined_def_id) {
+                (inlined_def_id, stability)
+            } else {
+                // For re-exports into crates without `staged_api`, reuse the original stability.
+                // This is necessary, because we always want to mark unstable items.
+                let def_id = self.def_id()?;
+                return tcx.lookup_stability(def_id);
+            }
+        } else {
+            let def_id = self.def_id()?;
+            let stability = tcx.lookup_stability(def_id)?;
+            (def_id, stability)
+        };
+
+        let StabilityLevel::Stable { mut since, allowed_through_unstable_modules: false } =
+            stability.level
+        else {
+            return Some(stability);
+        };
+
+        // If any of the item's ancestors was stabilized later or is still unstable,
+        // then report the ancestor's stability instead.
+        while let Some(parent_def_id) = tcx.opt_parent(def_id) {
+            if let Some(parent_stability) = tcx.lookup_stability(parent_def_id) {
+                match parent_stability.level {
+                    StabilityLevel::Unstable { .. } => return Some(parent_stability),
+                    StabilityLevel::Stable { since: parent_since, .. } => {
+                        if parent_since > since {
+                            stability = parent_stability;
+                            since = parent_since;
+                        }
+                    }
+                }
+            }
+            def_id = parent_def_id;
+        }
+        Some(stability)
     }
 
     pub(crate) fn const_stability(&self, tcx: TyCtxt<'_>) -> Option<ConstStability> {
diff --git a/tests/rustdoc/const-display.rs b/tests/rustdoc/const-display.rs
index ac55a6302f785..a71825d883d6a 100644
--- a/tests/rustdoc/const-display.rs
+++ b/tests/rustdoc/const-display.rs
@@ -1,8 +1,6 @@
 #![crate_name = "foo"]
 
-#![unstable(feature = "humans",
-            reason = "who ever let humans program computers, we're apparently really bad at it",
-            issue = "none")]
+#![stable(feature = "rust1", since = "1.0.0")]
 
 #![feature(foo, foo2)]
 #![feature(staged_api)]
@@ -48,10 +46,18 @@ pub const unsafe fn foo2_gated() -> u32 { 42 }
 #[rustc_const_stable(feature = "rust1", since = "1.0.0")]
 pub const unsafe fn bar2_gated() -> u32 { 42 }
 
-//@ has 'foo/fn.bar_not_gated.html' '//pre' 'pub const unsafe fn bar_not_gated() -> u32'
-//@ !hasraw - '//span[@class="since"]'
-pub const unsafe fn bar_not_gated() -> u32 { 42 }
+#[unstable(
+    feature = "humans",
+    reason = "who ever let humans program computers, we're apparently really bad at it",
+    issue = "none",
+)]
+pub mod unstable {
+    //@ has 'foo/unstable/fn.bar_not_gated.html' '//pre' 'pub const unsafe fn bar_not_gated() -> u32'
+    //@ !hasraw - '//span[@class="since"]'
+    pub const unsafe fn bar_not_gated() -> u32 { 42 }
+}
 
+#[stable(feature = "rust1", since = "1.0.0")]
 pub struct Foo;
 
 impl Foo {
diff --git a/tests/rustdoc/stability.rs b/tests/rustdoc/stability.rs
index 270da822c009b..de855b43ba538 100644
--- a/tests/rustdoc/stability.rs
+++ b/tests/rustdoc/stability.rs
@@ -1,6 +1,6 @@
 #![feature(staged_api)]
 
-#![unstable(feature = "test", issue = "none")]
+#![stable(feature = "rust1", since = "1.0.0")]
 
 //@ has stability/index.html
 //@ has - '//ul[@class="item-table"]/li[1]//a' AaStable
@@ -10,6 +10,7 @@
 #[stable(feature = "rust2", since = "2.2.2")]
 pub struct AaStable;
 
+#[unstable(feature = "test", issue = "none")]
 pub struct Unstable {
     //@ has stability/struct.Unstable.html \
     //      '//span[@class="item-info"]//div[@class="stab unstable"]' \
@@ -21,3 +22,31 @@ pub struct Unstable {
 
 #[stable(feature = "rust2", since = "2.2.2")]
 pub struct ZzStable;
+
+#[unstable(feature = "unstable", issue = "none")]
+pub mod unstable {
+    //@ !hasraw stability/unstable/struct.Foo.html '//span[@class="since"]'
+    //@ has - '//div[@class="stab unstable"]' 'experimental'
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub struct Foo;
+}
+
+#[stable(feature = "rust2", since = "2.2.2")]
+pub mod stable_later {
+    //@ has stability/stable_later/struct.Bar.html '//span[@class="since"]' '2.2.2'
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub struct Bar;
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub mod stable_earlier {
+    //@ has stability/stable_earlier/struct.Foo.html '//span[@class="since"]' '1.0.0'
+    #[doc(inline)]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub use crate::unstable::Foo;
+
+    //@ has stability/stable_earlier/struct.Bar.html '//span[@class="since"]' '1.0.0'
+    #[doc(inline)]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub use crate::stable_later::Bar;
+}

From 46ecb23198fa83136a266cb5a18675d2d342ab18 Mon Sep 17 00:00:00 2001
From: Lukas Markeffsky <@>
Date: Sun, 15 Sep 2024 16:47:42 +0200
Subject: [PATCH 08/14] unify dyn* coercions with other pointer coercions

---
 compiler/rustc_borrowck/src/type_check/mod.rs |  2 +-
 compiler/rustc_codegen_cranelift/src/base.rs  |  6 ++++-
 compiler/rustc_codegen_ssa/src/mir/rvalue.rs  |  2 +-
 .../src/check_consts/check.rs                 | 12 +++++-----
 .../rustc_const_eval/src/interpret/cast.rs    |  2 +-
 compiler/rustc_hir_typeck/src/cast.rs         | 22 +++++++++----------
 compiler/rustc_hir_typeck/src/coercion.rs     |  5 ++++-
 .../rustc_hir_typeck/src/expr_use_visitor.rs  |  7 ++----
 compiler/rustc_middle/src/mir/statement.rs    |  1 -
 compiler/rustc_middle/src/mir/syntax.rs       |  2 --
 compiler/rustc_middle/src/ty/adjustment.rs    |  6 ++---
 compiler/rustc_middle/src/ty/cast.rs          |  6 -----
 compiler/rustc_mir_build/src/thir/cx/expr.rs  |  1 -
 .../src/mentioned_items.rs                    |  6 ++---
 compiler/rustc_mir_transform/src/validate.rs  |  6 ++---
 compiler/rustc_monomorphize/src/collector.rs  |  6 ++---
 .../rustc_smir/src/rustc_smir/convert/mir.rs  |  3 ++-
 .../rustc_smir/src/rustc_smir/convert/ty.rs   |  1 +
 compiler/stable_mir/src/mir/body.rs           |  1 +
 .../clippy_utils/src/qualify_min_const_fn.rs  |  2 +-
 tests/ui/dyn-star/dyn-to-rigid.rs             |  2 +-
 tests/ui/dyn-star/dyn-to-rigid.stderr         |  6 ++---
 tests/ui/dyn-star/enum-cast.rs                | 18 +++++++++++++++
 23 files changed, 70 insertions(+), 55 deletions(-)
 create mode 100644 tests/ui/dyn-star/enum-cast.rs

diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 4056b42354898..29a0c5bdf572f 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -2139,7 +2139,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         );
                     }
 
-                    CastKind::DynStar => {
+                    CastKind::PointerCoercion(PointerCoercion::DynStar) => {
                         // get the constraints from the target type (`dyn* Clone`)
                         //
                         // apply them to prove that the source type `Foo` implements `Clone` etc
diff --git a/compiler/rustc_codegen_cranelift/src/base.rs b/compiler/rustc_codegen_cranelift/src/base.rs
index dc342e151f33c..876466e79bc07 100644
--- a/compiler/rustc_codegen_cranelift/src/base.rs
+++ b/compiler/rustc_codegen_cranelift/src/base.rs
@@ -770,7 +770,11 @@ fn codegen_stmt<'tcx>(
                     let operand = codegen_operand(fx, operand);
                     crate::unsize::coerce_unsized_into(fx, operand, lval);
                 }
-                Rvalue::Cast(CastKind::DynStar, ref operand, _) => {
+                Rvalue::Cast(
+                    CastKind::PointerCoercion(PointerCoercion::DynStar),
+                    ref operand,
+                    _,
+                ) => {
                     let operand = codegen_operand(fx, operand);
                     crate::unsize::coerce_dyn_star(fx, operand, lval);
                 }
diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
index ad0e03fc2630d..dc5377bf9d457 100644
--- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
@@ -526,7 +526,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             bug!("unexpected non-pair operand");
                         }
                     }
-                    mir::CastKind::DynStar => {
+                    mir::CastKind::PointerCoercion(PointerCoercion::DynStar) => {
                         let (lldata, llextra) = operand.val.pointer_parts();
                         let (lldata, llextra) =
                             base::cast_to_dyn_star(bx, lldata, operand.layout, cast.ty, llextra);
diff --git a/compiler/rustc_const_eval/src/check_consts/check.rs b/compiler/rustc_const_eval/src/check_consts/check.rs
index 2c33ff9d219f3..dc7cdee00b2be 100644
--- a/compiler/rustc_const_eval/src/check_consts/check.rs
+++ b/compiler/rustc_const_eval/src/check_consts/check.rs
@@ -447,8 +447,12 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                 // These are all okay; they only change the type, not the data.
             }
 
-            Rvalue::Cast(CastKind::PointerCoercion(PointerCoercion::Unsize), _, _) => {
-                // Unsizing is implemented for CTFE.
+            Rvalue::Cast(
+                CastKind::PointerCoercion(PointerCoercion::Unsize | PointerCoercion::DynStar),
+                _,
+                _,
+            ) => {
+                // Unsizing and `dyn*` coercions are implemented for CTFE.
             }
 
             Rvalue::Cast(CastKind::PointerExposeProvenance, _, _) => {
@@ -458,10 +462,6 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                 // Since no pointer can ever get exposed (rejected above), this is easy to support.
             }
 
-            Rvalue::Cast(CastKind::DynStar, _, _) => {
-                // `dyn*` coercion is implemented for CTFE.
-            }
-
             Rvalue::Cast(_, _, _) => {}
 
             Rvalue::NullaryOp(
diff --git a/compiler/rustc_const_eval/src/interpret/cast.rs b/compiler/rustc_const_eval/src/interpret/cast.rs
index 70d074cfdc59c..25fb5f12d61a6 100644
--- a/compiler/rustc_const_eval/src/interpret/cast.rs
+++ b/compiler/rustc_const_eval/src/interpret/cast.rs
@@ -125,7 +125,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 }
             }
 
-            CastKind::DynStar => {
+            CastKind::PointerCoercion(PointerCoercion::DynStar) => {
                 if let ty::Dynamic(data, _, ty::DynStar) = cast_ty.kind() {
                     // Initial cast from sized to dyn trait
                     let vtable = self.get_vtable_ptr(src.layout.ty, data)?;
diff --git a/compiler/rustc_hir_typeck/src/cast.rs b/compiler/rustc_hir_typeck/src/cast.rs
index aab0c4c116afe..9e20e1d9745a7 100644
--- a/compiler/rustc_hir_typeck/src/cast.rs
+++ b/compiler/rustc_hir_typeck/src/cast.rs
@@ -33,12 +33,12 @@ use rustc_errors::codes::*;
 use rustc_errors::{Applicability, Diag, ErrorGuaranteed};
 use rustc_hir::{self as hir, ExprKind};
 use rustc_macros::{TypeFoldable, TypeVisitable};
-use rustc_middle::bug;
 use rustc_middle::mir::Mutability;
 use rustc_middle::ty::adjustment::AllowTwoPhase;
 use rustc_middle::ty::cast::{CastKind, CastTy};
 use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeAndMut, TypeVisitableExt, VariantDef};
+use rustc_middle::{bug, span_bug};
 use rustc_session::lint;
 use rustc_span::def_id::LOCAL_CRATE;
 use rustc_span::symbol::sym;
@@ -674,6 +674,16 @@ impl<'a, 'tcx> CastCheck<'tcx> {
         use rustc_middle::ty::cast::CastTy::*;
         use rustc_middle::ty::cast::IntTy::*;
 
+        if self.cast_ty.is_dyn_star() {
+            if fcx.tcx.features().dyn_star {
+                span_bug!(self.span, "should be handled by `coerce`");
+            } else {
+                // Report "casting is invalid" rather than "non-primitive cast"
+                // if the feature is not enabled.
+                return Err(CastError::IllegalCast);
+            }
+        }
+
         let (t_from, t_cast) = match (CastTy::from_ty(self.expr_ty), CastTy::from_ty(self.cast_ty))
         {
             (Some(t_from), Some(t_cast)) => (t_from, t_cast),
@@ -780,16 +790,6 @@ impl<'a, 'tcx> CastCheck<'tcx> {
             (Int(Char) | Int(Bool), Int(_)) => Ok(CastKind::PrimIntCast),
 
             (Int(_) | Float, Int(_) | Float) => Ok(CastKind::NumericCast),
-
-            (_, DynStar) => {
-                if fcx.tcx.features().dyn_star {
-                    bug!("should be handled by `coerce`")
-                } else {
-                    Err(CastError::IllegalCast)
-                }
-            }
-
-            (DynStar, _) => Err(CastError::IllegalCast),
         }
     }
 
diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs
index 7be91d78e19f6..b08c5bc6d9a36 100644
--- a/compiler/rustc_hir_typeck/src/coercion.rs
+++ b/compiler/rustc_hir_typeck/src/coercion.rs
@@ -769,7 +769,10 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
         ));
 
         Ok(InferOk {
-            value: (vec![Adjustment { kind: Adjust::DynStar, target: b }], b),
+            value: (
+                vec![Adjustment { kind: Adjust::Pointer(PointerCoercion::DynStar), target: b }],
+                b,
+            ),
             obligations,
         })
     }
diff --git a/compiler/rustc_hir_typeck/src/expr_use_visitor.rs b/compiler/rustc_hir_typeck/src/expr_use_visitor.rs
index 29feed56290b8..bb5f351137305 100644
--- a/compiler/rustc_hir_typeck/src/expr_use_visitor.rs
+++ b/compiler/rustc_hir_typeck/src/expr_use_visitor.rs
@@ -759,9 +759,7 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
         for adjustment in adjustments {
             debug!("walk_adjustment expr={:?} adj={:?}", expr, adjustment);
             match adjustment.kind {
-                adjustment::Adjust::NeverToAny
-                | adjustment::Adjust::Pointer(_)
-                | adjustment::Adjust::DynStar => {
+                adjustment::Adjust::NeverToAny | adjustment::Adjust::Pointer(_) => {
                     // Creating a closure/fn-pointer or unsizing consumes
                     // the input and stores it into the resulting rvalue.
                     self.consume_or_copy(&place_with_id, place_with_id.hir_id);
@@ -1296,8 +1294,7 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
             adjustment::Adjust::NeverToAny
             | adjustment::Adjust::Pointer(_)
             | adjustment::Adjust::Borrow(_)
-            | adjustment::Adjust::ReborrowPin(..)
-            | adjustment::Adjust::DynStar => {
+            | adjustment::Adjust::ReborrowPin(..) => {
                 // Result is an rvalue.
                 Ok(self.cat_rvalue(expr.hir_id, target))
             }
diff --git a/compiler/rustc_middle/src/mir/statement.rs b/compiler/rustc_middle/src/mir/statement.rs
index bc7dfa6205e71..c3891e70e9358 100644
--- a/compiler/rustc_middle/src/mir/statement.rs
+++ b/compiler/rustc_middle/src/mir/statement.rs
@@ -434,7 +434,6 @@ impl<'tcx> Rvalue<'tcx> {
                 | CastKind::PtrToPtr
                 | CastKind::PointerCoercion(_)
                 | CastKind::PointerWithExposedProvenance
-                | CastKind::DynStar
                 | CastKind::Transmute,
                 _,
                 _,
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index 231eb1989834c..ff7360f06ed19 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -1404,8 +1404,6 @@ pub enum CastKind {
     ///
     /// Both are runtime nops, so should be [`CastKind::PtrToPtr`] instead in runtime MIR.
     PointerCoercion(PointerCoercion),
-    /// Cast into a dyn* object.
-    DynStar,
     IntToInt,
     FloatToInt,
     FloatToFloat,
diff --git a/compiler/rustc_middle/src/ty/adjustment.rs b/compiler/rustc_middle/src/ty/adjustment.rs
index 5a32078760e5b..41a20e89cbf78 100644
--- a/compiler/rustc_middle/src/ty/adjustment.rs
+++ b/compiler/rustc_middle/src/ty/adjustment.rs
@@ -35,6 +35,9 @@ pub enum PointerCoercion {
     /// type. Codegen backends and miri figure out what has to be done
     /// based on the precise source/target type at hand.
     Unsize,
+
+    /// Go from a pointer-like type to a `dyn*` object.
+    DynStar,
 }
 
 /// Represents coercing a value to a different type of value.
@@ -102,9 +105,6 @@ pub enum Adjust<'tcx> {
 
     Pointer(PointerCoercion),
 
-    /// Cast into a dyn* object.
-    DynStar,
-
     /// Take a pinned reference and reborrow as a `Pin<&mut T>` or `Pin<&T>`.
     ReborrowPin(ty::Region<'tcx>, hir::Mutability),
 }
diff --git a/compiler/rustc_middle/src/ty/cast.rs b/compiler/rustc_middle/src/ty/cast.rs
index 46f3765953678..b1316ceef5ac7 100644
--- a/compiler/rustc_middle/src/ty/cast.rs
+++ b/compiler/rustc_middle/src/ty/cast.rs
@@ -34,15 +34,12 @@ pub enum CastTy<'tcx> {
     FnPtr,
     /// Raw pointers.
     Ptr(ty::TypeAndMut<'tcx>),
-    /// Casting into a `dyn*` value.
-    DynStar,
 }
 
 /// Cast Kind. See [RFC 401](https://rust-lang.github.io/rfcs/0401-coercions.html)
 /// (or rustc_hir_analysis/check/cast.rs).
 #[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
 pub enum CastKind {
-    CoercionCast,
     PtrPtrCast,
     PtrAddrCast,
     AddrPtrCast,
@@ -53,7 +50,6 @@ pub enum CastKind {
     ArrayPtrCast,
     FnPtrPtrCast,
     FnPtrAddrCast,
-    DynStarCast,
 }
 
 impl<'tcx> CastTy<'tcx> {
@@ -71,7 +67,6 @@ impl<'tcx> CastTy<'tcx> {
             ty::Adt(d, _) if d.is_enum() && d.is_payloadfree() => Some(CastTy::Int(IntTy::CEnum)),
             ty::RawPtr(ty, mutbl) => Some(CastTy::Ptr(ty::TypeAndMut { ty, mutbl })),
             ty::FnPtr(..) => Some(CastTy::FnPtr),
-            ty::Dynamic(_, _, ty::DynStar) => Some(CastTy::DynStar),
             _ => None,
         }
     }
@@ -86,7 +81,6 @@ pub fn mir_cast_kind<'tcx>(from_ty: Ty<'tcx>, cast_ty: Ty<'tcx>) -> mir::CastKin
             mir::CastKind::PointerExposeProvenance
         }
         (Some(CastTy::Int(_)), Some(CastTy::Ptr(_))) => mir::CastKind::PointerWithExposedProvenance,
-        (_, Some(CastTy::DynStar)) => mir::CastKind::DynStar,
         (Some(CastTy::Int(_)), Some(CastTy::Int(_))) => mir::CastKind::IntToInt,
         (Some(CastTy::FnPtr), Some(CastTy::Ptr(_))) => mir::CastKind::FnPtrToPtr,
 
diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index 55236933922ff..a3764b5d312aa 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -146,7 +146,6 @@ impl<'tcx> Cx<'tcx> {
             Adjust::Borrow(AutoBorrow::RawPtr(mutability)) => {
                 ExprKind::RawBorrow { mutability, arg: self.thir.exprs.push(expr) }
             }
-            Adjust::DynStar => ExprKind::Cast { source: self.thir.exprs.push(expr) },
             Adjust::ReborrowPin(region, mutbl) => {
                 debug!("apply ReborrowPin adjustment");
                 // Rewrite `$expr` as `Pin { __pointer: &(mut)? *($expr).__pointer }`
diff --git a/compiler/rustc_mir_transform/src/mentioned_items.rs b/compiler/rustc_mir_transform/src/mentioned_items.rs
index f24de609e6b29..9f9b39b02d39e 100644
--- a/compiler/rustc_mir_transform/src/mentioned_items.rs
+++ b/compiler/rustc_mir_transform/src/mentioned_items.rs
@@ -70,11 +70,11 @@ impl<'tcx> Visitor<'tcx> for MentionedItemsVisitor<'_, 'tcx> {
         match *rvalue {
             // We need to detect unsizing casts that required vtables.
             mir::Rvalue::Cast(
-                mir::CastKind::PointerCoercion(PointerCoercion::Unsize),
+                mir::CastKind::PointerCoercion(PointerCoercion::Unsize)
+                | mir::CastKind::PointerCoercion(PointerCoercion::DynStar),
                 ref operand,
                 target_ty,
-            )
-            | mir::Rvalue::Cast(mir::CastKind::DynStar, ref operand, target_ty) => {
+            ) => {
                 // This isn't monomorphized yet so we can't tell what the actual types are -- just
                 // add everything that may involve a vtable.
                 let source_ty = operand.ty(self.body, self.tcx);
diff --git a/compiler/rustc_mir_transform/src/validate.rs b/compiler/rustc_mir_transform/src/validate.rs
index 914dddc1a56ea..2b6498409d046 100644
--- a/compiler/rustc_mir_transform/src/validate.rs
+++ b/compiler/rustc_mir_transform/src/validate.rs
@@ -1128,9 +1128,6 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
             Rvalue::Cast(kind, operand, target_type) => {
                 let op_ty = operand.ty(self.body, self.tcx);
                 match kind {
-                    CastKind::DynStar => {
-                        // FIXME(dyn-star): make sure nothing needs to be done here.
-                    }
                     // FIXME: Add Checks for these
                     CastKind::PointerWithExposedProvenance | CastKind::PointerExposeProvenance => {}
                     CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer) => {
@@ -1208,6 +1205,9 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                         // This is used for all `CoerceUnsized` types,
                         // not just pointers/references, so is hard to check.
                     }
+                    CastKind::PointerCoercion(PointerCoercion::DynStar) => {
+                        // FIXME(dyn-star): make sure nothing needs to be done here.
+                    }
                     CastKind::IntToInt | CastKind::IntToFloat => {
                         let input_valid = op_ty.is_integral() || op_ty.is_char() || op_ty.is_bool();
                         let target_valid = target_type.is_numeric() || target_type.is_char();
diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs
index 8d137b8d8f9f1..986d0030a2406 100644
--- a/compiler/rustc_monomorphize/src/collector.rs
+++ b/compiler/rustc_monomorphize/src/collector.rs
@@ -665,11 +665,11 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirUsedCollector<'a, 'tcx> {
             // have to instantiate all methods of the trait being cast to, so we
             // can build the appropriate vtable.
             mir::Rvalue::Cast(
-                mir::CastKind::PointerCoercion(PointerCoercion::Unsize),
+                mir::CastKind::PointerCoercion(PointerCoercion::Unsize)
+                | mir::CastKind::PointerCoercion(PointerCoercion::DynStar),
                 ref operand,
                 target_ty,
-            )
-            | mir::Rvalue::Cast(mir::CastKind::DynStar, ref operand, target_ty) => {
+            ) => {
                 let source_ty = operand.ty(self.body, self.tcx);
                 // *Before* monomorphizing, record that we already handled this mention.
                 self.used_mentioned_items
diff --git a/compiler/rustc_smir/src/rustc_smir/convert/mir.rs b/compiler/rustc_smir/src/rustc_smir/convert/mir.rs
index f4c7fd7c90066..e702503724240 100644
--- a/compiler/rustc_smir/src/rustc_smir/convert/mir.rs
+++ b/compiler/rustc_smir/src/rustc_smir/convert/mir.rs
@@ -282,11 +282,12 @@ impl<'tcx> Stable<'tcx> for mir::CastKind {
     type T = stable_mir::mir::CastKind;
     fn stable(&self, tables: &mut Tables<'_>) -> Self::T {
         use rustc_middle::mir::CastKind::*;
+        use rustc_middle::ty::adjustment::PointerCoercion;
         match self {
             PointerExposeProvenance => stable_mir::mir::CastKind::PointerExposeAddress,
             PointerWithExposedProvenance => stable_mir::mir::CastKind::PointerWithExposedProvenance,
+            PointerCoercion(PointerCoercion::DynStar) => stable_mir::mir::CastKind::DynStar,
             PointerCoercion(c) => stable_mir::mir::CastKind::PointerCoercion(c.stable(tables)),
-            DynStar => stable_mir::mir::CastKind::DynStar,
             IntToInt => stable_mir::mir::CastKind::IntToInt,
             FloatToInt => stable_mir::mir::CastKind::FloatToInt,
             FloatToFloat => stable_mir::mir::CastKind::FloatToFloat,
diff --git a/compiler/rustc_smir/src/rustc_smir/convert/ty.rs b/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
index e54ab1f7e24c3..ac9a023576261 100644
--- a/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
+++ b/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
@@ -119,6 +119,7 @@ impl<'tcx> Stable<'tcx> for ty::adjustment::PointerCoercion {
             }
             PointerCoercion::ArrayToPointer => stable_mir::mir::PointerCoercion::ArrayToPointer,
             PointerCoercion::Unsize => stable_mir::mir::PointerCoercion::Unsize,
+            PointerCoercion::DynStar => unreachable!("represented as `CastKind::DynStar` in smir"),
         }
     }
 }
diff --git a/compiler/stable_mir/src/mir/body.rs b/compiler/stable_mir/src/mir/body.rs
index 7c09fe1a08541..ab9fc218d19fb 100644
--- a/compiler/stable_mir/src/mir/body.rs
+++ b/compiler/stable_mir/src/mir/body.rs
@@ -960,6 +960,7 @@ pub enum CastKind {
     PointerExposeAddress,
     PointerWithExposedProvenance,
     PointerCoercion(PointerCoercion),
+    // FIXME(smir-rename): change this to PointerCoercion(DynStar)
     DynStar,
     IntToInt,
     FloatToInt,
diff --git a/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs b/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
index d9befb3c157a3..6434c2f42cfb9 100644
--- a/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
+++ b/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
@@ -154,7 +154,7 @@ fn check_rvalue<'tcx>(
         Rvalue::Cast(CastKind::PointerExposeProvenance, _, _) => {
             Err((span, "casting pointers to ints is unstable in const fn".into()))
         },
-        Rvalue::Cast(CastKind::DynStar, _, _) => {
+        Rvalue::Cast(CastKind::PointerCoercion(PointerCoercion::DynStar), _, _) => {
             // FIXME(dyn-star)
             unimplemented!()
         },
diff --git a/tests/ui/dyn-star/dyn-to-rigid.rs b/tests/ui/dyn-star/dyn-to-rigid.rs
index e80ee15902eef..dc33e288f24e6 100644
--- a/tests/ui/dyn-star/dyn-to-rigid.rs
+++ b/tests/ui/dyn-star/dyn-to-rigid.rs
@@ -5,7 +5,7 @@ trait Tr {}
 
 fn f(x: dyn* Tr) -> usize {
     x as usize
-    //~^ ERROR casting `(dyn* Tr + 'static)` as `usize` is invalid
+    //~^ ERROR non-primitive cast: `(dyn* Tr + 'static)` as `usize`
 }
 
 fn main() {}
diff --git a/tests/ui/dyn-star/dyn-to-rigid.stderr b/tests/ui/dyn-star/dyn-to-rigid.stderr
index b198c5245dea0..49b8f268aa4e9 100644
--- a/tests/ui/dyn-star/dyn-to-rigid.stderr
+++ b/tests/ui/dyn-star/dyn-to-rigid.stderr
@@ -1,9 +1,9 @@
-error[E0606]: casting `(dyn* Tr + 'static)` as `usize` is invalid
+error[E0605]: non-primitive cast: `(dyn* Tr + 'static)` as `usize`
   --> $DIR/dyn-to-rigid.rs:7:5
    |
 LL |     x as usize
-   |     ^^^^^^^^^^
+   |     ^^^^^^^^^^ an `as` expression can only be used to convert between primitive types or to coerce to a specific trait object
 
 error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0606`.
+For more information about this error, try `rustc --explain E0605`.
diff --git a/tests/ui/dyn-star/enum-cast.rs b/tests/ui/dyn-star/enum-cast.rs
new file mode 100644
index 0000000000000..6e895e9527aba
--- /dev/null
+++ b/tests/ui/dyn-star/enum-cast.rs
@@ -0,0 +1,18 @@
+//@ check-pass
+
+// This used to ICE, because the compiler confused a pointer-like to dyn* coercion
+// with a c-like enum to integer cast.
+
+#![feature(dyn_star)]
+#![expect(incomplete_features)]
+
+enum E {
+    Num(usize),
+}
+
+trait Trait {}
+impl Trait for E {}
+
+fn main() {
+    let _ = E::Num(42) as dyn* Trait;
+}

From b52dea823090223ee2e6faaf08210d085bbc52f2 Mon Sep 17 00:00:00 2001
From: Lukas Markeffsky <@>
Date: Tue, 10 Sep 2024 21:41:50 +0200
Subject: [PATCH 09/14] add another test

---
 .../ui/cast/ptr-to-trait-obj-different-regions-misc.rs |  5 +++++
 .../ptr-to-trait-obj-different-regions-misc.stderr     | 10 +++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/tests/ui/cast/ptr-to-trait-obj-different-regions-misc.rs b/tests/ui/cast/ptr-to-trait-obj-different-regions-misc.rs
index 01c347bfae5a0..d7c6c50d8bebc 100644
--- a/tests/ui/cast/ptr-to-trait-obj-different-regions-misc.rs
+++ b/tests/ui/cast/ptr-to-trait-obj-different-regions-misc.rs
@@ -33,5 +33,10 @@ fn change_assoc_1<'a, 'b>(
            //~| error: lifetime may not live long enough
 }
 
+// This tests the default borrow check error, without the special casing for return values.
+fn require_static(_: *const dyn Trait<'static>) {}
+fn extend_to_static<'a>(ptr: *const dyn Trait<'a>) {
+    require_static(ptr as _) //~ error: lifetime may not live long enough
+}
 
 fn main() {}
diff --git a/tests/ui/cast/ptr-to-trait-obj-different-regions-misc.stderr b/tests/ui/cast/ptr-to-trait-obj-different-regions-misc.stderr
index 7044e4dec1fe5..4a699780c647f 100644
--- a/tests/ui/cast/ptr-to-trait-obj-different-regions-misc.stderr
+++ b/tests/ui/cast/ptr-to-trait-obj-different-regions-misc.stderr
@@ -132,5 +132,13 @@ help: `'b` and `'a` must be the same: replace one with the other
    |
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error: aborting due to 8 previous errors
+error: lifetime may not live long enough
+  --> $DIR/ptr-to-trait-obj-different-regions-misc.rs:39:20
+   |
+LL | fn extend_to_static<'a>(ptr: *const dyn Trait<'a>) {
+   |                     -- lifetime `'a` defined here
+LL |     require_static(ptr as _)
+   |                    ^^^ cast requires that `'a` must outlive `'static`
+
+error: aborting due to 9 previous errors
 

From d1e82d438f9f3d2ce59be210a2710c560e93e688 Mon Sep 17 00:00:00 2001
From: Lukas Markeffsky <@>
Date: Tue, 10 Sep 2024 18:47:10 +0200
Subject: [PATCH 10/14] use more accurate spans for user type ascriptions

---
 compiler/rustc_middle/src/thir.rs                  |  4 +++-
 compiler/rustc_middle/src/thir/visit.rs            |  3 ++-
 .../rustc_mir_build/src/build/expr/as_place.rs     | 14 ++++++++------
 compiler/rustc_mir_build/src/thir/cx/expr.rs       | 13 +++++++++++--
 compiler/rustc_mir_build/src/thir/print.rs         |  6 ++++--
 ...dress_of_reborrow.SimplifyCfg-initial.after.mir | 12 ++++++------
 ...t-obj-different-regions-id-trait.current.stderr |  4 ++--
 ...rait-obj-different-regions-id-trait.next.stderr |  4 ++--
 tests/ui/kindck/kindck-impl-type-params.stderr     |  4 ++--
 .../user-annotations/cast_static_lifetime.stderr   |  3 +--
 .../type_ascription_static_lifetime.stderr         |  7 +++----
 .../trait-upcasting/type-checking-test-3.stderr    |  8 ++++----
 .../trait-upcasting/type-checking-test-4.stderr    |  8 ++++----
 13 files changed, 52 insertions(+), 38 deletions(-)

diff --git a/compiler/rustc_middle/src/thir.rs b/compiler/rustc_middle/src/thir.rs
index 32234d6b55d66..5b4f10e52adbf 100644
--- a/compiler/rustc_middle/src/thir.rs
+++ b/compiler/rustc_middle/src/thir.rs
@@ -453,12 +453,14 @@ pub enum ExprKind<'tcx> {
         source: ExprId,
         /// Type that the user gave to this expression
         user_ty: UserTy<'tcx>,
+        user_ty_span: Span,
     },
-    /// A type ascription on a value, e.g. `42: i32`.
+    /// A type ascription on a value, e.g. `type_ascribe!(42, i32)` or `42 as i32`.
     ValueTypeAscription {
         source: ExprId,
         /// Type that the user gave to this expression
         user_ty: UserTy<'tcx>,
+        user_ty_span: Span,
     },
     /// A closure definition.
     Closure(Box<ClosureExpr<'tcx>>),
diff --git a/compiler/rustc_middle/src/thir/visit.rs b/compiler/rustc_middle/src/thir/visit.rs
index e246ecebbec0b..af2e914cbf1a0 100644
--- a/compiler/rustc_middle/src/thir/visit.rs
+++ b/compiler/rustc_middle/src/thir/visit.rs
@@ -129,7 +129,8 @@ pub fn walk_expr<'thir, 'tcx: 'thir, V: Visitor<'thir, 'tcx>>(
                 visitor.visit_expr(&visitor.thir()[base.base]);
             }
         }
-        PlaceTypeAscription { source, user_ty: _ } | ValueTypeAscription { source, user_ty: _ } => {
+        PlaceTypeAscription { source, user_ty: _, user_ty_span: _ }
+        | ValueTypeAscription { source, user_ty: _, user_ty_span: _ } => {
             visitor.visit_expr(&visitor.thir()[source])
         }
         Closure(box ClosureExpr {
diff --git a/compiler/rustc_mir_build/src/build/expr/as_place.rs b/compiler/rustc_mir_build/src/build/expr/as_place.rs
index 2084bcae7b79e..c7298e3ddfa90 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_place.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_place.rs
@@ -470,21 +470,22 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 block.and(place_builder)
             }
 
-            ExprKind::PlaceTypeAscription { source, ref user_ty } => {
+            ExprKind::PlaceTypeAscription { source, ref user_ty, user_ty_span } => {
                 let place_builder = unpack!(
                     block = this.expr_as_place(block, source, mutability, fake_borrow_temps,)
                 );
                 if let Some(user_ty) = user_ty {
+                    let ty_source_info = this.source_info(user_ty_span);
                     let annotation_index =
                         this.canonical_user_type_annotations.push(CanonicalUserTypeAnnotation {
-                            span: source_info.span,
+                            span: user_ty_span,
                             user_ty: user_ty.clone(),
                             inferred_ty: expr.ty,
                         });
 
                     let place = place_builder.to_place(this);
                     this.cfg.push(block, Statement {
-                        source_info,
+                        source_info: ty_source_info,
                         kind: StatementKind::AscribeUserType(
                             Box::new((place, UserTypeProjection {
                                 base: annotation_index,
@@ -496,20 +497,21 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 }
                 block.and(place_builder)
             }
-            ExprKind::ValueTypeAscription { source, ref user_ty } => {
+            ExprKind::ValueTypeAscription { source, ref user_ty, user_ty_span } => {
                 let source_expr = &this.thir[source];
                 let temp = unpack!(
                     block = this.as_temp(block, source_expr.temp_lifetime, source, mutability)
                 );
                 if let Some(user_ty) = user_ty {
+                    let ty_source_info = this.source_info(user_ty_span);
                     let annotation_index =
                         this.canonical_user_type_annotations.push(CanonicalUserTypeAnnotation {
-                            span: source_info.span,
+                            span: user_ty_span,
                             user_ty: user_ty.clone(),
                             inferred_ty: expr.ty,
                         });
                     this.cfg.push(block, Statement {
-                        source_info,
+                        source_info: ty_source_info,
                         kind: StatementKind::AscribeUserType(
                             Box::new((Place::from(temp), UserTypeProjection {
                                 base: annotation_index,
diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index a3764b5d312aa..00c6a1a4b49fa 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -840,6 +840,7 @@ impl<'tcx> Cx<'tcx> {
                     ExprKind::ValueTypeAscription {
                         source: cast_expr,
                         user_ty: Some(Box::new(*user_ty)),
+                        user_ty_span: cast_ty.span,
                     }
                 } else {
                     cast
@@ -851,9 +852,17 @@ impl<'tcx> Cx<'tcx> {
                 debug!("make_mirror_unadjusted: (type) user_ty={:?}", user_ty);
                 let mirrored = self.mirror_expr(source);
                 if source.is_syntactic_place_expr() {
-                    ExprKind::PlaceTypeAscription { source: mirrored, user_ty }
+                    ExprKind::PlaceTypeAscription {
+                        source: mirrored,
+                        user_ty,
+                        user_ty_span: ty.span,
+                    }
                 } else {
-                    ExprKind::ValueTypeAscription { source: mirrored, user_ty }
+                    ExprKind::ValueTypeAscription {
+                        source: mirrored,
+                        user_ty,
+                        user_ty_span: ty.span,
+                    }
                 }
             }
             hir::ExprKind::DropTemps(source) => ExprKind::Use { source: self.mirror_expr(source) },
diff --git a/compiler/rustc_mir_build/src/thir/print.rs b/compiler/rustc_mir_build/src/thir/print.rs
index ce7774f594882..a507aeb76acd9 100644
--- a/compiler/rustc_mir_build/src/thir/print.rs
+++ b/compiler/rustc_mir_build/src/thir/print.rs
@@ -454,16 +454,18 @@ impl<'a, 'tcx> ThirPrinter<'a, 'tcx> {
                 self.print_adt_expr(&**adt_expr, depth_lvl + 1);
                 print_indented!(self, "}", depth_lvl);
             }
-            PlaceTypeAscription { source, user_ty } => {
+            PlaceTypeAscription { source, user_ty, user_ty_span } => {
                 print_indented!(self, "PlaceTypeAscription {", depth_lvl);
                 print_indented!(self, format!("user_ty: {:?}", user_ty), depth_lvl + 1);
+                print_indented!(self, format!("user_ty_span: {:?}", user_ty_span), depth_lvl + 1);
                 print_indented!(self, "source:", depth_lvl + 1);
                 self.print_expr(*source, depth_lvl + 2);
                 print_indented!(self, "}", depth_lvl);
             }
-            ValueTypeAscription { source, user_ty } => {
+            ValueTypeAscription { source, user_ty, user_ty_span } => {
                 print_indented!(self, "ValueTypeAscription {", depth_lvl);
                 print_indented!(self, format!("user_ty: {:?}", user_ty), depth_lvl + 1);
+                print_indented!(self, format!("user_ty_span: {:?}", user_ty_span), depth_lvl + 1);
                 print_indented!(self, "source:", depth_lvl + 1);
                 self.print_expr(*source, depth_lvl + 2);
                 print_indented!(self, "}", depth_lvl);
diff --git a/tests/mir-opt/address_of.address_of_reborrow.SimplifyCfg-initial.after.mir b/tests/mir-opt/address_of.address_of_reborrow.SimplifyCfg-initial.after.mir
index be636da4517ca..edf62a1e17398 100644
--- a/tests/mir-opt/address_of.address_of_reborrow.SimplifyCfg-initial.after.mir
+++ b/tests/mir-opt/address_of.address_of_reborrow.SimplifyCfg-initial.after.mir
@@ -1,8 +1,8 @@
 // MIR for `address_of_reborrow` after SimplifyCfg-initial
 
 | User Type Annotations
-| 0: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [CanonicalVarInfo { kind: Ty(General(U0)) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:8:5: 8:18, inferred_ty: *const [i32; 10]
-| 1: user_ty: Canonical { value: Ty(*const dyn std::marker::Send), max_universe: U0, variables: [CanonicalVarInfo { kind: Region(U0) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:10:5: 10:25, inferred_ty: *const dyn std::marker::Send
+| 0: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [CanonicalVarInfo { kind: Ty(General(U0)) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:8:10: 8:18, inferred_ty: *const [i32; 10]
+| 1: user_ty: Canonical { value: Ty(*const dyn std::marker::Send), max_universe: U0, variables: [CanonicalVarInfo { kind: Region(U0) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:10:10: 10:25, inferred_ty: *const dyn std::marker::Send
 | 2: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [CanonicalVarInfo { kind: Ty(General(U0)) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:14:12: 14:20, inferred_ty: *const [i32; 10]
 | 3: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [CanonicalVarInfo { kind: Ty(General(U0)) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:14:12: 14:20, inferred_ty: *const [i32; 10]
 | 4: user_ty: Canonical { value: Ty(*const [i32; 10]), max_universe: U0, variables: [], defining_opaque_types: [] }, span: $DIR/address_of.rs:15:12: 15:28, inferred_ty: *const [i32; 10]
@@ -11,8 +11,8 @@
 | 7: user_ty: Canonical { value: Ty(*const dyn std::marker::Send), max_universe: U0, variables: [CanonicalVarInfo { kind: Region(U0) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:16:12: 16:27, inferred_ty: *const dyn std::marker::Send
 | 8: user_ty: Canonical { value: Ty(*const [i32]), max_universe: U0, variables: [], defining_opaque_types: [] }, span: $DIR/address_of.rs:17:12: 17:24, inferred_ty: *const [i32]
 | 9: user_ty: Canonical { value: Ty(*const [i32]), max_universe: U0, variables: [], defining_opaque_types: [] }, span: $DIR/address_of.rs:17:12: 17:24, inferred_ty: *const [i32]
-| 10: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [CanonicalVarInfo { kind: Ty(General(U0)) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:19:5: 19:18, inferred_ty: *const [i32; 10]
-| 11: user_ty: Canonical { value: Ty(*const dyn std::marker::Send), max_universe: U0, variables: [CanonicalVarInfo { kind: Region(U0) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:21:5: 21:25, inferred_ty: *const dyn std::marker::Send
+| 10: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [CanonicalVarInfo { kind: Ty(General(U0)) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:19:10: 19:18, inferred_ty: *const [i32; 10]
+| 11: user_ty: Canonical { value: Ty(*const dyn std::marker::Send), max_universe: U0, variables: [CanonicalVarInfo { kind: Region(U0) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:21:10: 21:25, inferred_ty: *const dyn std::marker::Send
 | 12: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [CanonicalVarInfo { kind: Ty(General(U0)) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:24:12: 24:20, inferred_ty: *const [i32; 10]
 | 13: user_ty: Canonical { value: Ty(*const ^0), max_universe: U0, variables: [CanonicalVarInfo { kind: Ty(General(U0)) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:24:12: 24:20, inferred_ty: *const [i32; 10]
 | 14: user_ty: Canonical { value: Ty(*const [i32; 10]), max_universe: U0, variables: [], defining_opaque_types: [] }, span: $DIR/address_of.rs:25:12: 25:28, inferred_ty: *const [i32; 10]
@@ -21,8 +21,8 @@
 | 17: user_ty: Canonical { value: Ty(*const dyn std::marker::Send), max_universe: U0, variables: [CanonicalVarInfo { kind: Region(U0) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:26:12: 26:27, inferred_ty: *const dyn std::marker::Send
 | 18: user_ty: Canonical { value: Ty(*const [i32]), max_universe: U0, variables: [], defining_opaque_types: [] }, span: $DIR/address_of.rs:27:12: 27:24, inferred_ty: *const [i32]
 | 19: user_ty: Canonical { value: Ty(*const [i32]), max_universe: U0, variables: [], defining_opaque_types: [] }, span: $DIR/address_of.rs:27:12: 27:24, inferred_ty: *const [i32]
-| 20: user_ty: Canonical { value: Ty(*mut ^0), max_universe: U0, variables: [CanonicalVarInfo { kind: Ty(General(U0)) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:29:5: 29:16, inferred_ty: *mut [i32; 10]
-| 21: user_ty: Canonical { value: Ty(*mut dyn std::marker::Send), max_universe: U0, variables: [CanonicalVarInfo { kind: Region(U0) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:31:5: 31:23, inferred_ty: *mut dyn std::marker::Send
+| 20: user_ty: Canonical { value: Ty(*mut ^0), max_universe: U0, variables: [CanonicalVarInfo { kind: Ty(General(U0)) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:29:10: 29:16, inferred_ty: *mut [i32; 10]
+| 21: user_ty: Canonical { value: Ty(*mut dyn std::marker::Send), max_universe: U0, variables: [CanonicalVarInfo { kind: Region(U0) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:31:10: 31:23, inferred_ty: *mut dyn std::marker::Send
 | 22: user_ty: Canonical { value: Ty(*mut ^0), max_universe: U0, variables: [CanonicalVarInfo { kind: Ty(General(U0)) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:34:12: 34:18, inferred_ty: *mut [i32; 10]
 | 23: user_ty: Canonical { value: Ty(*mut ^0), max_universe: U0, variables: [CanonicalVarInfo { kind: Ty(General(U0)) }], defining_opaque_types: [] }, span: $DIR/address_of.rs:34:12: 34:18, inferred_ty: *mut [i32; 10]
 | 24: user_ty: Canonical { value: Ty(*mut [i32; 10]), max_universe: U0, variables: [], defining_opaque_types: [] }, span: $DIR/address_of.rs:35:12: 35:26, inferred_ty: *mut [i32; 10]
diff --git a/tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.current.stderr b/tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.current.stderr
index 5a5b4bfcacf43..4e43d3b93fa35 100644
--- a/tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.current.stderr
+++ b/tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.current.stderr
@@ -1,11 +1,11 @@
 error: lifetime may not live long enough
-  --> $DIR/ptr-to-trait-obj-different-regions-id-trait.rs:24:17
+  --> $DIR/ptr-to-trait-obj-different-regions-id-trait.rs:24:27
    |
 LL | fn m<'a>() {
    |      -- lifetime `'a` defined here
 LL |     let unsend: *const dyn Cat<'a> = &();
 LL |     let _send = unsend as *const S<dyn Cat<'static>>;
-   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
+   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
    |
    = note: requirement occurs because of the type `S<dyn Cat<'_>>`, which makes the generic argument `dyn Cat<'_>` invariant
    = note: the struct `S<T>` is invariant over the parameter `T`
diff --git a/tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.next.stderr b/tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.next.stderr
index 5a5b4bfcacf43..4e43d3b93fa35 100644
--- a/tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.next.stderr
+++ b/tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.next.stderr
@@ -1,11 +1,11 @@
 error: lifetime may not live long enough
-  --> $DIR/ptr-to-trait-obj-different-regions-id-trait.rs:24:17
+  --> $DIR/ptr-to-trait-obj-different-regions-id-trait.rs:24:27
    |
 LL | fn m<'a>() {
    |      -- lifetime `'a` defined here
 LL |     let unsend: *const dyn Cat<'a> = &();
 LL |     let _send = unsend as *const S<dyn Cat<'static>>;
-   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
+   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
    |
    = note: requirement occurs because of the type `S<dyn Cat<'_>>`, which makes the generic argument `dyn Cat<'_>` invariant
    = note: the struct `S<T>` is invariant over the parameter `T`
diff --git a/tests/ui/kindck/kindck-impl-type-params.stderr b/tests/ui/kindck/kindck-impl-type-params.stderr
index aad020e4ec97a..5892596dc6adc 100644
--- a/tests/ui/kindck/kindck-impl-type-params.stderr
+++ b/tests/ui/kindck/kindck-impl-type-params.stderr
@@ -112,13 +112,13 @@ LL |     struct Foo; // does not impl Copy
    |
 
 error: lifetime may not live long enough
-  --> $DIR/kindck-impl-type-params.rs:30:13
+  --> $DIR/kindck-impl-type-params.rs:30:19
    |
 LL | fn foo<'a>() {
    |        -- lifetime `'a` defined here
 LL |     let t: S<&'a isize> = S(marker::PhantomData);
 LL |     let a = &t as &dyn Gettable<&'a isize>;
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
 
 error: aborting due to 7 previous errors
 
diff --git a/tests/ui/nll/user-annotations/cast_static_lifetime.stderr b/tests/ui/nll/user-annotations/cast_static_lifetime.stderr
index 35eec233ed5c0..efd14fe875dbe 100644
--- a/tests/ui/nll/user-annotations/cast_static_lifetime.stderr
+++ b/tests/ui/nll/user-annotations/cast_static_lifetime.stderr
@@ -4,10 +4,9 @@ error[E0597]: `x` does not live long enough
 LL |     let x = 22_u32;
    |         - binding `x` declared here
 LL |     let y: &u32 = (&x) as &'static u32;
-   |                   ^^^^----------------
+   |                   ^^^^    ------------ type annotation requires that `x` is borrowed for `'static`
    |                   |
    |                   borrowed value does not live long enough
-   |                   type annotation requires that `x` is borrowed for `'static`
 LL | }
    | - `x` dropped here while still borrowed
 
diff --git a/tests/ui/nll/user-annotations/type_ascription_static_lifetime.stderr b/tests/ui/nll/user-annotations/type_ascription_static_lifetime.stderr
index 3e2706309b342..2ed0fadc06557 100644
--- a/tests/ui/nll/user-annotations/type_ascription_static_lifetime.stderr
+++ b/tests/ui/nll/user-annotations/type_ascription_static_lifetime.stderr
@@ -4,10 +4,9 @@ error[E0597]: `x` does not live long enough
 LL |     let x = 22_u32;
    |         - binding `x` declared here
 LL |     let y: &u32 = type_ascribe!(&x, &'static u32);
-   |                   --------------^^---------------
-   |                   |             |
-   |                   |             borrowed value does not live long enough
-   |                   type annotation requires that `x` is borrowed for `'static`
+   |                                 ^^  ------------ type annotation requires that `x` is borrowed for `'static`
+   |                                 |
+   |                                 borrowed value does not live long enough
 LL | }
    | - `x` dropped here while still borrowed
 
diff --git a/tests/ui/traits/trait-upcasting/type-checking-test-3.stderr b/tests/ui/traits/trait-upcasting/type-checking-test-3.stderr
index e6cb6a753998f..0a969b611e9d3 100644
--- a/tests/ui/traits/trait-upcasting/type-checking-test-3.stderr
+++ b/tests/ui/traits/trait-upcasting/type-checking-test-3.stderr
@@ -1,18 +1,18 @@
 error: lifetime may not live long enough
-  --> $DIR/type-checking-test-3.rs:11:13
+  --> $DIR/type-checking-test-3.rs:11:18
    |
 LL | fn test_wrong1<'a>(x: &dyn Foo<'static>, y: &'a u32) {
    |                -- lifetime `'a` defined here
 LL |     let _ = x as &dyn Bar<'a>; // Error
-   |             ^^^^^^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
+   |                  ^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
 
 error: lifetime may not live long enough
-  --> $DIR/type-checking-test-3.rs:16:13
+  --> $DIR/type-checking-test-3.rs:16:18
    |
 LL | fn test_wrong2<'a>(x: &dyn Foo<'a>) {
    |                -- lifetime `'a` defined here
 LL |     let _ = x as &dyn Bar<'static>; // Error
-   |             ^^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
+   |                  ^^^^^^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/traits/trait-upcasting/type-checking-test-4.stderr b/tests/ui/traits/trait-upcasting/type-checking-test-4.stderr
index ccced5875778d..090120a2327a8 100644
--- a/tests/ui/traits/trait-upcasting/type-checking-test-4.stderr
+++ b/tests/ui/traits/trait-upcasting/type-checking-test-4.stderr
@@ -1,18 +1,18 @@
 error: lifetime may not live long enough
-  --> $DIR/type-checking-test-4.rs:19:13
+  --> $DIR/type-checking-test-4.rs:19:18
    |
 LL | fn test_wrong1<'a>(x: &dyn Foo<'static>, y: &'a u32) {
    |                -- lifetime `'a` defined here
 LL |     let _ = x as &dyn Bar<'static, 'a>; // Error
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
+   |                  ^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
 
 error: lifetime may not live long enough
-  --> $DIR/type-checking-test-4.rs:24:13
+  --> $DIR/type-checking-test-4.rs:24:18
    |
 LL | fn test_wrong2<'a>(x: &dyn Foo<'static>, y: &'a u32) {
    |                -- lifetime `'a` defined here
 LL |     let _ = x as &dyn Bar<'a, 'static>; // Error
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
+   |                  ^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
 
 error: lifetime may not live long enough
   --> $DIR/type-checking-test-4.rs:30:5

From 5e60d1f87e5c4abebb9a4eae9d68955113399d6e Mon Sep 17 00:00:00 2001
From: Lukas Markeffsky <@>
Date: Tue, 10 Sep 2024 19:20:27 +0200
Subject: [PATCH 11/14] replace "cast" with "coercion" where applicable

This changes the remaining span for the cast, because the new `Cast`
category has a higher priority (lower `Ord`) than the old `Coercion`
category, so we no longer report the region error for the "unsizing"
coercion from `*const Trait` to itself.
---
 .../src/diagnostics/explain_borrow.rs         |  4 ++-
 .../src/diagnostics/region_errors.rs          |  3 ++-
 compiler/rustc_borrowck/src/type_check/mod.rs | 26 +++++++++++--------
 compiler/rustc_middle/src/mir/query.rs        |  4 ++-
 .../two-phase-surprise-no-conflict.stderr     |  4 +--
 ...to-trait-obj-different-regions-misc.stderr |  2 +-
 .../dropck/dropck_trait_cycle_checked.stderr  | 12 ++++-----
 ...600-expected-return-static-indirect.stderr |  4 +--
 .../issue-54779-anon-static-lifetime.stderr   |  2 +-
 ...ore-lifetime-in-return-trait-object.stderr |  2 +-
 .../trait-object-lifetime-default-note.rs     |  2 +-
 .../trait-object-lifetime-default-note.stderr |  2 +-
 12 files changed, 38 insertions(+), 29 deletions(-)

diff --git a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
index 7077d78f45941..63b653bc9f4cb 100644
--- a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
@@ -333,7 +333,9 @@ impl<'tcx> BorrowExplanation<'tcx> {
                     }
                 }
 
-                if let ConstraintCategory::Cast { unsize_to: Some(unsize_ty) } = category {
+                if let ConstraintCategory::Cast { is_coercion: true, unsize_to: Some(unsize_ty) } =
+                    category
+                {
                     self.add_object_lifetime_default_note(tcx, err, unsize_ty);
                 }
                 self.add_lifetime_bound_suggestion_to_diagnostic(err, &category, span, region_name);
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index ca0a3c6613052..a4a9734de3f0f 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -47,7 +47,8 @@ impl<'tcx> ConstraintDescription for ConstraintCategory<'tcx> {
             ConstraintCategory::Yield => "yielding this value ",
             ConstraintCategory::UseAsConst => "using this value as a constant ",
             ConstraintCategory::UseAsStatic => "using this value as a static ",
-            ConstraintCategory::Cast { .. } => "cast ",
+            ConstraintCategory::Cast { is_coercion: false, .. } => "cast ",
+            ConstraintCategory::Cast { is_coercion: true, .. } => "coercion ",
             ConstraintCategory::CallArgument(_) => "argument ",
             ConstraintCategory::TypeAnnotation => "type annotation ",
             ConstraintCategory::ClosureBounds => "closure body ",
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 29a0c5bdf572f..db69f48e515a4 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -2007,7 +2007,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             self.prove_predicate(
                                 ty::ClauseKind::WellFormed(src_ty.into()),
                                 location.to_locations(),
-                                ConstraintCategory::Cast { unsize_to: None },
+                                ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
                             );
 
                             let src_ty = self.normalize(src_ty, location);
@@ -2015,7 +2015,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                                 src_ty,
                                 *ty,
                                 location.to_locations(),
-                                ConstraintCategory::Cast { unsize_to: None },
+                                ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
                             ) {
                                 span_mirbug!(
                                     self,
@@ -2036,7 +2036,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         self.prove_predicate(
                             ty::ClauseKind::WellFormed(src_ty.into()),
                             location.to_locations(),
-                            ConstraintCategory::Cast { unsize_to: None },
+                            ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
                         );
 
                         // The type that we see in the fcx is like
@@ -2049,7 +2049,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             src_ty,
                             *ty,
                             location.to_locations(),
-                            ConstraintCategory::Cast { unsize_to: None },
+                            ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
                         ) {
                             span_mirbug!(
                                 self,
@@ -2074,7 +2074,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             ty_fn_ptr_from,
                             *ty,
                             location.to_locations(),
-                            ConstraintCategory::Cast { unsize_to: None },
+                            ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
                         ) {
                             span_mirbug!(
                                 self,
@@ -2103,7 +2103,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             ty_fn_ptr_from,
                             *ty,
                             location.to_locations(),
-                            ConstraintCategory::Cast { unsize_to: None },
+                            ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
                         ) {
                             span_mirbug!(
                                 self,
@@ -2128,6 +2128,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             trait_ref,
                             location.to_locations(),
                             ConstraintCategory::Cast {
+                                is_coercion: true,
                                 unsize_to: Some(tcx.fold_regions(ty, |r, _| {
                                     if let ty::ReVar(_) = r.kind() {
                                         tcx.lifetimes.re_erased
@@ -2155,7 +2156,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                                 .iter()
                                 .map(|predicate| predicate.with_self_ty(tcx, self_ty)),
                             location.to_locations(),
-                            ConstraintCategory::Cast { unsize_to: None },
+                            ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
                         );
 
                         let outlives_predicate = tcx.mk_predicate(Binder::dummy(
@@ -2166,7 +2167,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         self.prove_predicate(
                             outlives_predicate,
                             location.to_locations(),
-                            ConstraintCategory::Cast { unsize_to: None },
+                            ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
                         );
                     }
 
@@ -2184,7 +2185,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             *ty_from,
                             *ty_to,
                             location.to_locations(),
-                            ConstraintCategory::Cast { unsize_to: None },
+                            ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
                         ) {
                             span_mirbug!(
                                 self,
@@ -2246,7 +2247,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             *ty_elem,
                             *ty_to,
                             location.to_locations(),
-                            ConstraintCategory::Cast { unsize_to: None },
+                            ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
                         ) {
                             span_mirbug!(
                                 self,
@@ -2427,7 +2428,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                                         src_obj,
                                         dst_obj,
                                         location.to_locations(),
-                                        ConstraintCategory::Cast { unsize_to: None },
+                                        ConstraintCategory::Cast {
+                                            is_coercion: false,
+                                            unsize_to: None,
+                                        },
                                     )
                                     .unwrap();
                                 }
diff --git a/compiler/rustc_middle/src/mir/query.rs b/compiler/rustc_middle/src/mir/query.rs
index 1002f64f849a2..47fea6f6d9057 100644
--- a/compiler/rustc_middle/src/mir/query.rs
+++ b/compiler/rustc_middle/src/mir/query.rs
@@ -234,7 +234,9 @@ pub enum ConstraintCategory<'tcx> {
     UseAsStatic,
     TypeAnnotation,
     Cast {
-        /// Whether this is an unsizing cast and if yes, this contains the target type.
+        /// Whether this cast is a coercion.
+        is_coercion: bool,
+        /// Whether this is an unsizing coercion and if yes, this contains the target type.
         /// Region variables are erased to ReErased.
         #[derive_where(skip)]
         unsize_to: Option<Ty<'tcx>>,
diff --git a/tests/ui/borrowck/two-phase-surprise-no-conflict.stderr b/tests/ui/borrowck/two-phase-surprise-no-conflict.stderr
index b3bf2f924fc3e..89b15a7a659dd 100644
--- a/tests/ui/borrowck/two-phase-surprise-no-conflict.stderr
+++ b/tests/ui/borrowck/two-phase-surprise-no-conflict.stderr
@@ -75,7 +75,7 @@ LL |     reg.register_univ(Box::new(CapturePass::new(&reg.sess_mut)));
    |     ^^^^^^^^^^^^^^^^^^-----------------------------------------^
    |     |                 |                         |
    |     |                 |                         immutable borrow occurs here
-   |     |                 cast requires that `reg.sess_mut` is borrowed for `'a`
+   |     |                 coercion requires that `reg.sess_mut` is borrowed for `'a`
    |     mutable borrow occurs here
    |
    = note: due to object lifetime defaults, `Box<dyn for<'b> LateLintPass<'b>>` actually means `Box<(dyn for<'b> LateLintPass<'b> + 'static)>`
@@ -119,7 +119,7 @@ LL |     reg.register_univ(Box::new(CapturePass::new_mut(&mut reg.sess_mut)));
    |     ^^^^^^^^^^^^^^^^^^-------------------------------------------------^
    |     |                 |                             |
    |     |                 |                             first mutable borrow occurs here
-   |     |                 cast requires that `reg.sess_mut` is borrowed for `'a`
+   |     |                 coercion requires that `reg.sess_mut` is borrowed for `'a`
    |     second mutable borrow occurs here
    |
    = note: due to object lifetime defaults, `Box<dyn for<'b> LateLintPass<'b>>` actually means `Box<(dyn for<'b> LateLintPass<'b> + 'static)>`
diff --git a/tests/ui/cast/ptr-to-trait-obj-different-regions-misc.stderr b/tests/ui/cast/ptr-to-trait-obj-different-regions-misc.stderr
index 4a699780c647f..6069f4f3b5563 100644
--- a/tests/ui/cast/ptr-to-trait-obj-different-regions-misc.stderr
+++ b/tests/ui/cast/ptr-to-trait-obj-different-regions-misc.stderr
@@ -138,7 +138,7 @@ error: lifetime may not live long enough
 LL | fn extend_to_static<'a>(ptr: *const dyn Trait<'a>) {
    |                     -- lifetime `'a` defined here
 LL |     require_static(ptr as _)
-   |                    ^^^ cast requires that `'a` must outlive `'static`
+   |                    ^^^^^^^^ cast requires that `'a` must outlive `'static`
 
 error: aborting due to 9 previous errors
 
diff --git a/tests/ui/dropck/dropck_trait_cycle_checked.stderr b/tests/ui/dropck/dropck_trait_cycle_checked.stderr
index 63fd07a91633d..f32736f1a674c 100644
--- a/tests/ui/dropck/dropck_trait_cycle_checked.stderr
+++ b/tests/ui/dropck/dropck_trait_cycle_checked.stderr
@@ -2,7 +2,7 @@ error[E0597]: `o2` does not live long enough
   --> $DIR/dropck_trait_cycle_checked.rs:111:13
    |
 LL |     let (o1, o2, o3): (Box<dyn Obj>, Box<dyn Obj>, Box<dyn Obj>) = (O::new(), O::new(), O::new());
-   |              -- binding `o2` declared here                          -------- cast requires that `o2` is borrowed for `'static`
+   |              -- binding `o2` declared here                          -------- coercion requires that `o2` is borrowed for `'static`
 LL |     o1.set0(&o2);
    |             ^^^ borrowed value does not live long enough
 ...
@@ -15,7 +15,7 @@ error[E0597]: `o3` does not live long enough
   --> $DIR/dropck_trait_cycle_checked.rs:112:13
    |
 LL |     let (o1, o2, o3): (Box<dyn Obj>, Box<dyn Obj>, Box<dyn Obj>) = (O::new(), O::new(), O::new());
-   |                  -- binding `o3` declared here                      -------- cast requires that `o3` is borrowed for `'static`
+   |                  -- binding `o3` declared here                      -------- coercion requires that `o3` is borrowed for `'static`
 LL |     o1.set0(&o2);
 LL |     o1.set1(&o3);
    |             ^^^ borrowed value does not live long enough
@@ -29,7 +29,7 @@ error[E0597]: `o2` does not live long enough
   --> $DIR/dropck_trait_cycle_checked.rs:113:13
    |
 LL |     let (o1, o2, o3): (Box<dyn Obj>, Box<dyn Obj>, Box<dyn Obj>) = (O::new(), O::new(), O::new());
-   |              -- binding `o2` declared here                                    -------- cast requires that `o2` is borrowed for `'static`
+   |              -- binding `o2` declared here                                    -------- coercion requires that `o2` is borrowed for `'static`
 ...
 LL |     o2.set0(&o2);
    |             ^^^ borrowed value does not live long enough
@@ -43,7 +43,7 @@ error[E0597]: `o3` does not live long enough
   --> $DIR/dropck_trait_cycle_checked.rs:114:13
    |
 LL |     let (o1, o2, o3): (Box<dyn Obj>, Box<dyn Obj>, Box<dyn Obj>) = (O::new(), O::new(), O::new());
-   |                  -- binding `o3` declared here                                -------- cast requires that `o3` is borrowed for `'static`
+   |                  -- binding `o3` declared here                                -------- coercion requires that `o3` is borrowed for `'static`
 ...
 LL |     o2.set1(&o3);
    |             ^^^ borrowed value does not live long enough
@@ -57,7 +57,7 @@ error[E0597]: `o1` does not live long enough
   --> $DIR/dropck_trait_cycle_checked.rs:115:13
    |
 LL |     let (o1, o2, o3): (Box<dyn Obj>, Box<dyn Obj>, Box<dyn Obj>) = (O::new(), O::new(), O::new());
-   |          -- binding `o1` declared here                                                  -------- cast requires that `o1` is borrowed for `'static`
+   |          -- binding `o1` declared here                                                  -------- coercion requires that `o1` is borrowed for `'static`
 ...
 LL |     o3.set0(&o1);
    |             ^^^ borrowed value does not live long enough
@@ -71,7 +71,7 @@ error[E0597]: `o2` does not live long enough
   --> $DIR/dropck_trait_cycle_checked.rs:116:13
    |
 LL |     let (o1, o2, o3): (Box<dyn Obj>, Box<dyn Obj>, Box<dyn Obj>) = (O::new(), O::new(), O::new());
-   |              -- binding `o2` declared here                                              -------- cast requires that `o2` is borrowed for `'static`
+   |              -- binding `o2` declared here                                              -------- coercion requires that `o2` is borrowed for `'static`
 ...
 LL |     o3.set1(&o2);
    |             ^^^ borrowed value does not live long enough
diff --git a/tests/ui/lifetimes/issue-90600-expected-return-static-indirect.stderr b/tests/ui/lifetimes/issue-90600-expected-return-static-indirect.stderr
index 598f142419137..6bd6a0584c9f1 100644
--- a/tests/ui/lifetimes/issue-90600-expected-return-static-indirect.stderr
+++ b/tests/ui/lifetimes/issue-90600-expected-return-static-indirect.stderr
@@ -7,7 +7,7 @@ LL |     let refcell = RefCell::new(&mut foo);
    |                                ^^^^^^^^ borrowed value does not live long enough
 LL |
 LL |     let read = &refcell as &RefCell<dyn Read>;
-   |                -------- cast requires that `foo` is borrowed for `'static`
+   |                -------- coercion requires that `foo` is borrowed for `'static`
 ...
 LL | }
    |  - `foo` dropped here while still borrowed
@@ -19,7 +19,7 @@ LL | fn inner(mut foo: &[u8]) {
    |                   - let's call the lifetime of this reference `'1`
 ...
 LL |     let read = &refcell as &RefCell<dyn Read>;
-   |                ^^^^^^^^ cast requires that `'1` must outlive `'static`
+   |                ^^^^^^^^ coercion requires that `'1` must outlive `'static`
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/nll/issue-54779-anon-static-lifetime.stderr b/tests/ui/nll/issue-54779-anon-static-lifetime.stderr
index 92298c6617ff5..a454ed265685c 100644
--- a/tests/ui/nll/issue-54779-anon-static-lifetime.stderr
+++ b/tests/ui/nll/issue-54779-anon-static-lifetime.stderr
@@ -5,7 +5,7 @@ LL |         cx: &dyn DebugContext,
    |             - let's call the lifetime of this reference `'1`
 ...
 LL |         bar.debug_with(cx);
-   |                        ^^ cast requires that `'1` must outlive `'static`
+   |                        ^^ coercion requires that `'1` must outlive `'static`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/suggestions/lifetimes/suggest-using-tick-underscore-lifetime-in-return-trait-object.stderr b/tests/ui/suggestions/lifetimes/suggest-using-tick-underscore-lifetime-in-return-trait-object.stderr
index 73fa5ddb146e7..050ef7da9b936 100644
--- a/tests/ui/suggestions/lifetimes/suggest-using-tick-underscore-lifetime-in-return-trait-object.stderr
+++ b/tests/ui/suggestions/lifetimes/suggest-using-tick-underscore-lifetime-in-return-trait-object.stderr
@@ -4,7 +4,7 @@ error: lifetime may not live long enough
 LL | fn foo<T: Any>(value: &T) -> Box<dyn Any> {
    |                       - let's call the lifetime of this reference `'1`
 LL |     Box::new(value) as Box<dyn Any>
-   |     ^^^^^^^^^^^^^^^ cast requires that `'1` must outlive `'static`
+   |     ^^^^^^^^^^^^^^^ coercion requires that `'1` must outlive `'static`
    |
 help: to declare that the trait object captures data from argument `value`, you can add an explicit `'_` lifetime bound
    |
diff --git a/tests/ui/traits/trait-object-lifetime-default-note.rs b/tests/ui/traits/trait-object-lifetime-default-note.rs
index 31e3eb4ba4155..275411ff61c85 100644
--- a/tests/ui/traits/trait-object-lifetime-default-note.rs
+++ b/tests/ui/traits/trait-object-lifetime-default-note.rs
@@ -8,7 +8,7 @@ fn main() {
     //~| NOTE borrowed value does not live long enough
     //~| NOTE due to object lifetime defaults, `Box<dyn A>` actually means `Box<(dyn A + 'static)>`
     require_box(Box::new(r));
-    //~^ NOTE cast requires that `local` is borrowed for `'static`
+    //~^ NOTE coercion requires that `local` is borrowed for `'static`
 
     let _ = 0;
 } //~ NOTE `local` dropped here while still borrowed
diff --git a/tests/ui/traits/trait-object-lifetime-default-note.stderr b/tests/ui/traits/trait-object-lifetime-default-note.stderr
index 4244e34873ad1..8cb9bc0d80072 100644
--- a/tests/ui/traits/trait-object-lifetime-default-note.stderr
+++ b/tests/ui/traits/trait-object-lifetime-default-note.stderr
@@ -7,7 +7,7 @@ LL |     let r = &local;
    |             ^^^^^^ borrowed value does not live long enough
 ...
 LL |     require_box(Box::new(r));
-   |                 ----------- cast requires that `local` is borrowed for `'static`
+   |                 ----------- coercion requires that `local` is borrowed for `'static`
 ...
 LL | }
    | - `local` dropped here while still borrowed

From bd31e3ed70b75e5936880b18f6b5d1c8f5ee344f Mon Sep 17 00:00:00 2001
From: Lukas Markeffsky <@>
Date: Sun, 15 Sep 2024 19:35:06 +0200
Subject: [PATCH 12/14] be even more precise about "cast" vs "coercion"

---
 .../src/diagnostics/explain_borrow.rs         |  8 ++-
 .../src/diagnostics/region_errors.rs          |  4 +-
 compiler/rustc_borrowck/src/type_check/mod.rs | 69 +++++++++++--------
 compiler/rustc_codegen_cranelift/src/base.rs  | 11 +--
 compiler/rustc_codegen_ssa/src/mir/rvalue.rs  | 14 ++--
 .../src/check_consts/check.rs                 |  3 +-
 .../rustc_const_eval/src/interpret/cast.rs    | 11 +--
 compiler/rustc_middle/src/mir/query.rs        |  4 +-
 compiler/rustc_middle/src/mir/statement.rs    |  2 +-
 compiler/rustc_middle/src/mir/syntax.rs       | 13 +++-
 compiler/rustc_middle/src/thir.rs             |  2 +
 compiler/rustc_middle/src/thir/visit.rs       |  4 +-
 .../src/build/expr/as_rvalue.rs               |  6 +-
 .../rustc_mir_build/src/build/matches/test.rs | 10 ++-
 compiler/rustc_mir_build/src/thir/cx/expr.rs  | 26 +++++--
 compiler/rustc_mir_build/src/thir/print.rs    |  7 +-
 .../src/cleanup_post_borrowck.rs              |  1 +
 .../src/dataflow_const_prop.rs                |  2 +-
 compiler/rustc_mir_transform/src/gvn.rs       | 10 +--
 .../src/mentioned_items.rs                    |  8 +--
 .../src/shim/async_destructor_ctor.rs         |  9 +--
 compiler/rustc_mir_transform/src/validate.rs  | 14 ++--
 compiler/rustc_monomorphize/src/collector.rs  |  8 +--
 .../rustc_smir/src/rustc_smir/convert/mir.rs  |  4 +-
 .../clippy_utils/src/qualify_min_const_fn.rs  |  8 +--
 .../fail/dyn-upcast-trait-mismatch.stderr     |  2 +-
 ..._of_reborrow.SimplifyCfg-initial.after.mir | 26 +++----
 .../build_correct_coerce.main.built.after.mir |  2 +-
 ...ceiver_ptr_mutability.main.built.after.mir |  4 +-
 ...e_live_dead_in_statics.XXX.built.after.mir |  2 +-
 ...motion_extern_static.BAR.PromoteTemps.diff |  2 +-
 ...motion_extern_static.FOO.PromoteTemps.diff |  2 +-
 ...for_slices.main.GVN.32bit.panic-abort.diff |  2 +-
 ...or_slices.main.GVN.32bit.panic-unwind.diff |  2 +-
 ...for_slices.main.GVN.64bit.panic-abort.diff |  2 +-
 ...or_slices.main.GVN.64bit.panic-unwind.diff |  2 +-
 .../const_prop/reify_fn_ptr.main.GVN.diff     |  2 +-
 tests/mir-opt/const_prop/reify_fn_ptr.rs      |  2 +-
 .../slice_len.main.GVN.32bit.panic-abort.diff |  4 +-
 ...slice_len.main.GVN.32bit.panic-unwind.diff |  4 +-
 .../slice_len.main.GVN.64bit.panic-abort.diff |  4 +-
 ...slice_len.main.GVN.64bit.panic-unwind.diff |  4 +-
 tests/mir-opt/const_prop/slice_len.rs         |  2 +-
 ...ssue_107511.main.CopyProp.panic-abort.diff |  2 +-
 ...sue_107511.main.CopyProp.panic-unwind.diff |  2 +-
 ...oxed_slice.main.GVN.32bit.panic-abort.diff |  2 +-
 ...xed_slice.main.GVN.32bit.panic-unwind.diff |  2 +-
 ...oxed_slice.main.GVN.64bit.panic-abort.diff |  2 +-
 ...xed_slice.main.GVN.64bit.panic-unwind.diff |  2 +-
 ...n.DataflowConstProp.32bit.panic-abort.diff |  2 +-
 ....DataflowConstProp.32bit.panic-unwind.diff |  2 +-
 ...n.DataflowConstProp.64bit.panic-abort.diff |  2 +-
 ....DataflowConstProp.64bit.panic-unwind.diff |  2 +-
 .../gvn.array_len.GVN.panic-abort.diff        |  2 +-
 .../gvn.array_len.GVN.panic-unwind.diff       |  2 +-
 .../gvn.fn_pointers.GVN.panic-abort.diff      | 12 ++--
 .../gvn.fn_pointers.GVN.panic-unwind.diff     | 12 ++--
 ...n.wide_ptr_provenance.GVN.panic-abort.diff | 20 +++---
 ....wide_ptr_provenance.GVN.panic-unwind.diff | 20 +++---
 ...e_ptr_same_provenance.GVN.panic-abort.diff | 20 +++---
 ..._ptr_same_provenance.GVN.panic-unwind.diff | 20 +++---
 ...yn_trait.get_query.Inline.panic-abort.diff |  2 +-
 ...n_trait.get_query.Inline.panic-unwind.diff |  2 +-
 ....try_execute_query.Inline.panic-abort.diff |  2 +-
 ...try_execute_query.Inline.panic-unwind.diff |  2 +-
 ...implifyComparisonIntegral.panic-abort.diff |  2 +-
 ...mplifyComparisonIntegral.panic-unwind.diff |  2 +-
 ...array_len.array_bound.GVN.panic-abort.diff |  2 +-
 ...rray_len.array_bound.GVN.panic-unwind.diff |  2 +-
 ...y_len.array_bound_mut.GVN.panic-abort.diff |  2 +-
 ..._len.array_bound_mut.GVN.panic-unwind.diff |  2 +-
 ...r_array_len.array_len.GVN.panic-abort.diff |  2 +-
 ..._array_len.array_len.GVN.panic-unwind.diff |  2 +-
 ...en.array_len_by_value.GVN.panic-abort.diff |  2 +-
 ...n.array_len_by_value.GVN.panic-unwind.diff |  2 +-
 ...ray_len.array_len_raw.GVN.panic-abort.diff |  2 +-
 ...ay_len.array_len_raw.GVN.panic-unwind.diff |  2 +-
 ...en.array_len_reborrow.GVN.panic-abort.diff |  2 +-
 ...n.array_len_reborrow.GVN.panic-unwind.diff |  2 +-
 ...d_constant.main.GVN.32bit.panic-abort.diff |  2 +-
 ...d_constant.main.GVN.64bit.panic-abort.diff |  2 +-
 ...fg-pre-optimizations.after.panic-abort.mir |  2 +-
 ...g-pre-optimizations.after.panic-unwind.mir |  2 +-
 ...ls.c.SimplifyLocals-before-const-prop.diff |  2 +-
 ...mes.foo.ScalarReplacementOfAggregates.diff |  2 +-
 ...600-expected-return-static-indirect.stderr |  4 +-
 .../regions-close-object-into-object-4.stderr |  3 +-
 .../regions-close-object-into-object-5.stderr |  3 +-
 ...regions-close-over-type-parameter-1.stderr |  4 +-
 ...ore-lifetime-in-return-trait-object.stderr |  2 +-
 90 files changed, 289 insertions(+), 231 deletions(-)

diff --git a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
index 63b653bc9f4cb..31a5d451ff6b6 100644
--- a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
@@ -333,8 +333,10 @@ impl<'tcx> BorrowExplanation<'tcx> {
                     }
                 }
 
-                if let ConstraintCategory::Cast { is_coercion: true, unsize_to: Some(unsize_ty) } =
-                    category
+                if let ConstraintCategory::Cast {
+                    is_implicit_coercion: true,
+                    unsize_to: Some(unsize_ty),
+                } = category
                 {
                     self.add_object_lifetime_default_note(tcx, err, unsize_ty);
                 }
@@ -742,7 +744,7 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
                         // If we see an unsized cast, then if it is our data we should check
                         // whether it is being cast to a trait object.
                         Rvalue::Cast(
-                            CastKind::PointerCoercion(PointerCoercion::Unsize),
+                            CastKind::PointerCoercion(PointerCoercion::Unsize, _),
                             operand,
                             ty,
                         ) => {
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index a4a9734de3f0f..39175b406a4aa 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -47,8 +47,8 @@ impl<'tcx> ConstraintDescription for ConstraintCategory<'tcx> {
             ConstraintCategory::Yield => "yielding this value ",
             ConstraintCategory::UseAsConst => "using this value as a constant ",
             ConstraintCategory::UseAsStatic => "using this value as a static ",
-            ConstraintCategory::Cast { is_coercion: false, .. } => "cast ",
-            ConstraintCategory::Cast { is_coercion: true, .. } => "coercion ",
+            ConstraintCategory::Cast { is_implicit_coercion: false, .. } => "cast ",
+            ConstraintCategory::Cast { is_implicit_coercion: true, .. } => "coercion ",
             ConstraintCategory::CallArgument(_) => "argument ",
             ConstraintCategory::TypeAnnotation => "type annotation ",
             ConstraintCategory::ClosureBounds => "closure body ",
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index db69f48e515a4..16e51e82f85e0 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -1975,8 +1975,9 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             Rvalue::Cast(cast_kind, op, ty) => {
                 self.check_operand(op, location);
 
-                match cast_kind {
-                    CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer) => {
+                match *cast_kind {
+                    CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer, coercion_source) => {
+                        let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
                         let src_sig = op.ty(body, tcx).fn_sig(tcx);
 
                         // HACK: This shouldn't be necessary... We can remove this when we actually
@@ -2007,7 +2008,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             self.prove_predicate(
                                 ty::ClauseKind::WellFormed(src_ty.into()),
                                 location.to_locations(),
-                                ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
+                                ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
                             );
 
                             let src_ty = self.normalize(src_ty, location);
@@ -2015,7 +2016,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                                 src_ty,
                                 *ty,
                                 location.to_locations(),
-                                ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
+                                ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
                             ) {
                                 span_mirbug!(
                                     self,
@@ -2036,7 +2037,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         self.prove_predicate(
                             ty::ClauseKind::WellFormed(src_ty.into()),
                             location.to_locations(),
-                            ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
+                            ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
                         );
 
                         // The type that we see in the fcx is like
@@ -2049,7 +2050,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             src_ty,
                             *ty,
                             location.to_locations(),
-                            ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
+                            ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
                         ) {
                             span_mirbug!(
                                 self,
@@ -2062,19 +2063,23 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         }
                     }
 
-                    CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(safety)) => {
+                    CastKind::PointerCoercion(
+                        PointerCoercion::ClosureFnPointer(safety),
+                        coercion_source,
+                    ) => {
                         let sig = match op.ty(body, tcx).kind() {
                             ty::Closure(_, args) => args.as_closure().sig(),
                             _ => bug!(),
                         };
                         let ty_fn_ptr_from =
-                            Ty::new_fn_ptr(tcx, tcx.signature_unclosure(sig, *safety));
+                            Ty::new_fn_ptr(tcx, tcx.signature_unclosure(sig, safety));
 
+                        let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
                         if let Err(terr) = self.sub_types(
                             ty_fn_ptr_from,
                             *ty,
                             location.to_locations(),
-                            ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
+                            ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
                         ) {
                             span_mirbug!(
                                 self,
@@ -2087,7 +2092,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         }
                     }
 
-                    CastKind::PointerCoercion(PointerCoercion::UnsafeFnPointer) => {
+                    CastKind::PointerCoercion(
+                        PointerCoercion::UnsafeFnPointer,
+                        coercion_source,
+                    ) => {
                         let fn_sig = op.ty(body, tcx).fn_sig(tcx);
 
                         // The type that we see in the fcx is like
@@ -2099,11 +2107,12 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
                         let ty_fn_ptr_from = tcx.safe_to_unsafe_fn_ty(fn_sig);
 
+                        let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
                         if let Err(terr) = self.sub_types(
                             ty_fn_ptr_from,
                             *ty,
                             location.to_locations(),
-                            ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
+                            ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
                         ) {
                             span_mirbug!(
                                 self,
@@ -2116,7 +2125,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         }
                     }
 
-                    CastKind::PointerCoercion(PointerCoercion::Unsize) => {
+                    CastKind::PointerCoercion(PointerCoercion::Unsize, coercion_source) => {
                         let &ty = ty;
                         let trait_ref = ty::TraitRef::new(
                             tcx,
@@ -2124,23 +2133,21 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             [op.ty(body, tcx), ty],
                         );
 
+                        let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
+                        let unsize_to = tcx.fold_regions(ty, |r, _| {
+                            if let ty::ReVar(_) = r.kind() { tcx.lifetimes.re_erased } else { r }
+                        });
                         self.prove_trait_ref(
                             trait_ref,
                             location.to_locations(),
                             ConstraintCategory::Cast {
-                                is_coercion: true,
-                                unsize_to: Some(tcx.fold_regions(ty, |r, _| {
-                                    if let ty::ReVar(_) = r.kind() {
-                                        tcx.lifetimes.re_erased
-                                    } else {
-                                        r
-                                    }
-                                })),
+                                is_implicit_coercion,
+                                unsize_to: Some(unsize_to),
                             },
                         );
                     }
 
-                    CastKind::PointerCoercion(PointerCoercion::DynStar) => {
+                    CastKind::PointerCoercion(PointerCoercion::DynStar, coercion_source) => {
                         // get the constraints from the target type (`dyn* Clone`)
                         //
                         // apply them to prove that the source type `Foo` implements `Clone` etc
@@ -2151,12 +2158,13 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
                         let self_ty = op.ty(body, tcx);
 
+                        let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
                         self.prove_predicates(
                             existential_predicates
                                 .iter()
                                 .map(|predicate| predicate.with_self_ty(tcx, self_ty)),
                             location.to_locations(),
-                            ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
+                            ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
                         );
 
                         let outlives_predicate = tcx.mk_predicate(Binder::dummy(
@@ -2167,11 +2175,14 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         self.prove_predicate(
                             outlives_predicate,
                             location.to_locations(),
-                            ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
+                            ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
                         );
                     }
 
-                    CastKind::PointerCoercion(PointerCoercion::MutToConstPointer) => {
+                    CastKind::PointerCoercion(
+                        PointerCoercion::MutToConstPointer,
+                        coercion_source,
+                    ) => {
                         let ty::RawPtr(ty_from, hir::Mutability::Mut) = op.ty(body, tcx).kind()
                         else {
                             span_mirbug!(self, rvalue, "unexpected base type for cast {:?}", ty,);
@@ -2181,11 +2192,12 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             span_mirbug!(self, rvalue, "unexpected target type for cast {:?}", ty,);
                             return;
                         };
+                        let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
                         if let Err(terr) = self.sub_types(
                             *ty_from,
                             *ty_to,
                             location.to_locations(),
-                            ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
+                            ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
                         ) {
                             span_mirbug!(
                                 self,
@@ -2198,7 +2210,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         }
                     }
 
-                    CastKind::PointerCoercion(PointerCoercion::ArrayToPointer) => {
+                    CastKind::PointerCoercion(PointerCoercion::ArrayToPointer, coercion_source) => {
                         let ty_from = op.ty(body, tcx);
 
                         let opt_ty_elem_mut = match ty_from.kind() {
@@ -2243,11 +2255,12 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             return;
                         }
 
+                        let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
                         if let Err(terr) = self.sub_types(
                             *ty_elem,
                             *ty_to,
                             location.to_locations(),
-                            ConstraintCategory::Cast { is_coercion: true, unsize_to: None },
+                            ConstraintCategory::Cast { is_implicit_coercion, unsize_to: None },
                         ) {
                             span_mirbug!(
                                 self,
@@ -2429,7 +2442,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                                         dst_obj,
                                         location.to_locations(),
                                         ConstraintCategory::Cast {
-                                            is_coercion: false,
+                                            is_implicit_coercion: false,
                                             unsize_to: None,
                                         },
                                     )
diff --git a/compiler/rustc_codegen_cranelift/src/base.rs b/compiler/rustc_codegen_cranelift/src/base.rs
index 876466e79bc07..1ce0aacab4998 100644
--- a/compiler/rustc_codegen_cranelift/src/base.rs
+++ b/compiler/rustc_codegen_cranelift/src/base.rs
@@ -652,7 +652,7 @@ fn codegen_stmt<'tcx>(
                     lval.write_cvalue(fx, res);
                 }
                 Rvalue::Cast(
-                    CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer),
+                    CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer, _),
                     ref operand,
                     to_ty,
                 ) => {
@@ -677,7 +677,7 @@ fn codegen_stmt<'tcx>(
                     }
                 }
                 Rvalue::Cast(
-                    CastKind::PointerCoercion(PointerCoercion::UnsafeFnPointer),
+                    CastKind::PointerCoercion(PointerCoercion::UnsafeFnPointer, _),
                     ref operand,
                     to_ty,
                 ) => {
@@ -688,6 +688,7 @@ fn codegen_stmt<'tcx>(
                 Rvalue::Cast(
                     CastKind::PointerCoercion(
                         PointerCoercion::MutToConstPointer | PointerCoercion::ArrayToPointer,
+                        _,
                     ),
                     ..,
                 ) => {
@@ -741,7 +742,7 @@ fn codegen_stmt<'tcx>(
                     }
                 }
                 Rvalue::Cast(
-                    CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_)),
+                    CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_), _),
                     ref operand,
                     _to_ty,
                 ) => {
@@ -763,7 +764,7 @@ fn codegen_stmt<'tcx>(
                     }
                 }
                 Rvalue::Cast(
-                    CastKind::PointerCoercion(PointerCoercion::Unsize),
+                    CastKind::PointerCoercion(PointerCoercion::Unsize, _),
                     ref operand,
                     _to_ty,
                 ) => {
@@ -771,7 +772,7 @@ fn codegen_stmt<'tcx>(
                     crate::unsize::coerce_unsized_into(fx, operand, lval);
                 }
                 Rvalue::Cast(
-                    CastKind::PointerCoercion(PointerCoercion::DynStar),
+                    CastKind::PointerCoercion(PointerCoercion::DynStar, _),
                     ref operand,
                     _,
                 ) => {
diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
index dc5377bf9d457..f9c0f3ce94146 100644
--- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
@@ -34,7 +34,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             }
 
             mir::Rvalue::Cast(
-                mir::CastKind::PointerCoercion(PointerCoercion::Unsize),
+                mir::CastKind::PointerCoercion(PointerCoercion::Unsize, _),
                 ref source,
                 _,
             ) => {
@@ -465,7 +465,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         let lladdr = bx.ptrtoint(llptr, llcast_ty);
                         OperandValue::Immediate(lladdr)
                     }
-                    mir::CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer) => {
+                    mir::CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer, _) => {
                         match *operand.layout.ty.kind() {
                             ty::FnDef(def_id, args) => {
                                 let instance = ty::Instance::resolve_for_fn_ptr(
@@ -481,7 +481,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             _ => bug!("{} cannot be reified to a fn ptr", operand.layout.ty),
                         }
                     }
-                    mir::CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_)) => {
+                    mir::CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_), _) => {
                         match *operand.layout.ty.kind() {
                             ty::Closure(def_id, args) => {
                                 let instance = Instance::resolve_closure(
@@ -496,11 +496,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             _ => bug!("{} cannot be cast to a fn ptr", operand.layout.ty),
                         }
                     }
-                    mir::CastKind::PointerCoercion(PointerCoercion::UnsafeFnPointer) => {
+                    mir::CastKind::PointerCoercion(PointerCoercion::UnsafeFnPointer, _) => {
                         // This is a no-op at the LLVM level.
                         operand.val
                     }
-                    mir::CastKind::PointerCoercion(PointerCoercion::Unsize) => {
+                    mir::CastKind::PointerCoercion(PointerCoercion::Unsize, _) => {
                         assert!(bx.cx().is_backend_scalar_pair(cast));
                         let (lldata, llextra) = operand.val.pointer_parts();
                         let (lldata, llextra) =
@@ -508,7 +508,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         OperandValue::Pair(lldata, llextra)
                     }
                     mir::CastKind::PointerCoercion(
-                        PointerCoercion::MutToConstPointer | PointerCoercion::ArrayToPointer,
+                        PointerCoercion::MutToConstPointer | PointerCoercion::ArrayToPointer, _
                     ) => {
                         bug!("{kind:?} is for borrowck, and should never appear in codegen");
                     }
@@ -526,7 +526,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             bug!("unexpected non-pair operand");
                         }
                     }
-                    mir::CastKind::PointerCoercion(PointerCoercion::DynStar) => {
+                    mir::CastKind::PointerCoercion(PointerCoercion::DynStar, _) => {
                         let (lldata, llextra) = operand.val.pointer_parts();
                         let (lldata, llextra) =
                             base::cast_to_dyn_star(bx, lldata, operand.layout, cast.ty, llextra);
diff --git a/compiler/rustc_const_eval/src/check_consts/check.rs b/compiler/rustc_const_eval/src/check_consts/check.rs
index dc7cdee00b2be..e1b605979972d 100644
--- a/compiler/rustc_const_eval/src/check_consts/check.rs
+++ b/compiler/rustc_const_eval/src/check_consts/check.rs
@@ -440,6 +440,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                     | PointerCoercion::UnsafeFnPointer
                     | PointerCoercion::ClosureFnPointer(_)
                     | PointerCoercion::ReifyFnPointer,
+                    _,
                 ),
                 _,
                 _,
@@ -448,7 +449,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
             }
 
             Rvalue::Cast(
-                CastKind::PointerCoercion(PointerCoercion::Unsize | PointerCoercion::DynStar),
+                CastKind::PointerCoercion(PointerCoercion::Unsize | PointerCoercion::DynStar, _),
                 _,
                 _,
             ) => {
diff --git a/compiler/rustc_const_eval/src/interpret/cast.rs b/compiler/rustc_const_eval/src/interpret/cast.rs
index 25fb5f12d61a6..85e7d91c2ad50 100644
--- a/compiler/rustc_const_eval/src/interpret/cast.rs
+++ b/compiler/rustc_const_eval/src/interpret/cast.rs
@@ -32,7 +32,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
             if cast_ty == dest.layout.ty { dest.layout } else { self.layout_of(cast_ty)? };
         // FIXME: In which cases should we trigger UB when the source is uninit?
         match cast_kind {
-            CastKind::PointerCoercion(PointerCoercion::Unsize) => {
+            CastKind::PointerCoercion(PointerCoercion::Unsize, _) => {
                 self.unsize_into(src, cast_layout, dest)?;
             }
 
@@ -68,11 +68,12 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
 
             CastKind::PointerCoercion(
                 PointerCoercion::MutToConstPointer | PointerCoercion::ArrayToPointer,
+                _,
             ) => {
                 bug!("{cast_kind:?} casts are for borrowck only, not runtime MIR");
             }
 
-            CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer) => {
+            CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer, _) => {
                 // All reifications must be monomorphic, bail out otherwise.
                 ensure_monomorphic_enough(*self.tcx, src.layout.ty)?;
 
@@ -94,7 +95,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 }
             }
 
-            CastKind::PointerCoercion(PointerCoercion::UnsafeFnPointer) => {
+            CastKind::PointerCoercion(PointerCoercion::UnsafeFnPointer, _) => {
                 let src = self.read_immediate(src)?;
                 match cast_ty.kind() {
                     ty::FnPtr(..) => {
@@ -105,7 +106,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 }
             }
 
-            CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_)) => {
+            CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_), _) => {
                 // All reifications must be monomorphic, bail out otherwise.
                 ensure_monomorphic_enough(*self.tcx, src.layout.ty)?;
 
@@ -125,7 +126,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 }
             }
 
-            CastKind::PointerCoercion(PointerCoercion::DynStar) => {
+            CastKind::PointerCoercion(PointerCoercion::DynStar, _) => {
                 if let ty::Dynamic(data, _, ty::DynStar) = cast_ty.kind() {
                     // Initial cast from sized to dyn trait
                     let vtable = self.get_vtable_ptr(src.layout.ty, data)?;
diff --git a/compiler/rustc_middle/src/mir/query.rs b/compiler/rustc_middle/src/mir/query.rs
index 47fea6f6d9057..70331214ac5a8 100644
--- a/compiler/rustc_middle/src/mir/query.rs
+++ b/compiler/rustc_middle/src/mir/query.rs
@@ -234,8 +234,8 @@ pub enum ConstraintCategory<'tcx> {
     UseAsStatic,
     TypeAnnotation,
     Cast {
-        /// Whether this cast is a coercion.
-        is_coercion: bool,
+        /// Whether this cast is a coercion that was automatically inserted by the compiler.
+        is_implicit_coercion: bool,
         /// Whether this is an unsizing coercion and if yes, this contains the target type.
         /// Region variables are erased to ReErased.
         #[derive_where(skip)]
diff --git a/compiler/rustc_middle/src/mir/statement.rs b/compiler/rustc_middle/src/mir/statement.rs
index c3891e70e9358..88ed90c311463 100644
--- a/compiler/rustc_middle/src/mir/statement.rs
+++ b/compiler/rustc_middle/src/mir/statement.rs
@@ -432,7 +432,7 @@ impl<'tcx> Rvalue<'tcx> {
                 | CastKind::IntToFloat
                 | CastKind::FnPtrToPtr
                 | CastKind::PtrToPtr
-                | CastKind::PointerCoercion(_)
+                | CastKind::PointerCoercion(_, _)
                 | CastKind::PointerWithExposedProvenance
                 | CastKind::Transmute,
                 _,
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index ff7360f06ed19..bba3aee820ab2 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -579,7 +579,7 @@ pub struct CopyNonOverlapping<'tcx> {
     pub count: Operand<'tcx>,
 }
 
-/// Represents how a `TerminatorKind::Call` was constructed, used for diagnostics
+/// Represents how a [`TerminatorKind::Call`] was constructed, used for diagnostics.
 #[derive(Clone, Copy, TyEncodable, TyDecodable, Debug, PartialEq, Hash, HashStable)]
 #[derive(TypeFoldable, TypeVisitable)]
 pub enum CallSource {
@@ -1403,7 +1403,7 @@ pub enum CastKind {
     /// * [`PointerCoercion::MutToConstPointer`]
     ///
     /// Both are runtime nops, so should be [`CastKind::PtrToPtr`] instead in runtime MIR.
-    PointerCoercion(PointerCoercion),
+    PointerCoercion(PointerCoercion, CoercionSource),
     IntToInt,
     FloatToInt,
     FloatToFloat,
@@ -1419,6 +1419,15 @@ pub enum CastKind {
     Transmute,
 }
 
+/// Represents how a [`CastKind::PointerCoercion`] was constructed, used for diagnostics.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
+pub enum CoercionSource {
+    /// The coercion was manually written by the user with an `as` cast.
+    AsCast,
+    /// The coercion was automatically inserted by the compiler.
+    Implicit,
+}
+
 #[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
 #[derive(TypeFoldable, TypeVisitable)]
 pub enum AggregateKind<'tcx> {
diff --git a/compiler/rustc_middle/src/thir.rs b/compiler/rustc_middle/src/thir.rs
index 5b4f10e52adbf..e614d41899a0e 100644
--- a/compiler/rustc_middle/src/thir.rs
+++ b/compiler/rustc_middle/src/thir.rs
@@ -338,6 +338,8 @@ pub enum ExprKind<'tcx> {
     PointerCoercion {
         cast: PointerCoercion,
         source: ExprId,
+        /// Whether this coercion is written with an `as` cast in the source code.
+        is_from_as_cast: bool,
     },
     /// A `loop` expression.
     Loop {
diff --git a/compiler/rustc_middle/src/thir/visit.rs b/compiler/rustc_middle/src/thir/visit.rs
index af2e914cbf1a0..58e2ebaeaf8df 100644
--- a/compiler/rustc_middle/src/thir/visit.rs
+++ b/compiler/rustc_middle/src/thir/visit.rs
@@ -68,7 +68,9 @@ pub fn walk_expr<'thir, 'tcx: 'thir, V: Visitor<'thir, 'tcx>>(
         Cast { source } => visitor.visit_expr(&visitor.thir()[source]),
         Use { source } => visitor.visit_expr(&visitor.thir()[source]),
         NeverToAny { source } => visitor.visit_expr(&visitor.thir()[source]),
-        PointerCoercion { source, cast: _ } => visitor.visit_expr(&visitor.thir()[source]),
+        PointerCoercion { source, cast: _, is_from_as_cast: _ } => {
+            visitor.visit_expr(&visitor.thir()[source])
+        }
         Let { expr, ref pat } => {
             visitor.visit_expr(&visitor.thir()[expr]);
             visitor.visit_pat(pat);
diff --git a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs b/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
index ffedee8a1e816..fd949a533845e 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
@@ -292,7 +292,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 let cast_kind = mir_cast_kind(ty, expr.ty);
                 block.and(Rvalue::Cast(cast_kind, source, expr.ty))
             }
-            ExprKind::PointerCoercion { cast, source } => {
+            ExprKind::PointerCoercion { cast, source, is_from_as_cast } => {
                 let source = unpack!(
                     block = this.as_operand(
                         block,
@@ -302,7 +302,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         NeedsTemporary::No
                     )
                 );
-                block.and(Rvalue::Cast(CastKind::PointerCoercion(cast), source, expr.ty))
+                let origin =
+                    if is_from_as_cast { CoercionSource::AsCast } else { CoercionSource::Implicit };
+                block.and(Rvalue::Cast(CastKind::PointerCoercion(cast, origin), source, expr.ty))
             }
             ExprKind::Array { ref fields } => {
                 // (*) We would (maybe) be closer to codegen if we
diff --git a/compiler/rustc_mir_build/src/build/matches/test.rs b/compiler/rustc_mir_build/src/build/matches/test.rs
index 63873aad02a44..020c202f96503 100644
--- a/compiler/rustc_mir_build/src/build/matches/test.rs
+++ b/compiler/rustc_mir_build/src/build/matches/test.rs
@@ -407,7 +407,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         source_info,
                         temp,
                         Rvalue::Cast(
-                            CastKind::PointerCoercion(PointerCoercion::Unsize),
+                            CastKind::PointerCoercion(
+                                PointerCoercion::Unsize,
+                                CoercionSource::Implicit,
+                            ),
                             Operand::Copy(val),
                             ty,
                         ),
@@ -421,7 +424,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         source_info,
                         slice,
                         Rvalue::Cast(
-                            CastKind::PointerCoercion(PointerCoercion::Unsize),
+                            CastKind::PointerCoercion(
+                                PointerCoercion::Unsize,
+                                CoercionSource::Implicit,
+                            ),
                             expect,
                             ty,
                         ),
diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index 00c6a1a4b49fa..fbd45f59a4fb4 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -104,16 +104,29 @@ impl<'tcx> Cx<'tcx> {
         };
 
         let kind = match adjustment.kind {
-            Adjust::Pointer(PointerCoercion::Unsize) => {
-                adjust_span(&mut expr);
+            Adjust::Pointer(cast) => {
+                if cast == PointerCoercion::Unsize {
+                    adjust_span(&mut expr);
+                }
+
+                let is_from_as_cast = if let hir::Node::Expr(hir::Expr {
+                    kind: hir::ExprKind::Cast(..),
+                    span: cast_span,
+                    ..
+                }) = self.tcx.parent_hir_node(hir_expr.hir_id)
+                {
+                    // Use the whole span of the `x as T` expression for the coercion.
+                    span = *cast_span;
+                    true
+                } else {
+                    false
+                };
                 ExprKind::PointerCoercion {
-                    cast: PointerCoercion::Unsize,
+                    cast,
                     source: self.thir.exprs.push(expr),
+                    is_from_as_cast,
                 }
             }
-            Adjust::Pointer(cast) => {
-                ExprKind::PointerCoercion { cast, source: self.thir.exprs.push(expr) }
-            }
             Adjust::NeverToAny if adjustment.target.is_never() => return expr,
             Adjust::NeverToAny => ExprKind::NeverToAny { source: self.thir.exprs.push(expr) },
             Adjust::Deref(None) => {
@@ -235,6 +248,7 @@ impl<'tcx> Cx<'tcx> {
             ExprKind::PointerCoercion {
                 source: self.mirror_expr(source),
                 cast: PointerCoercion::ArrayToPointer,
+                is_from_as_cast: true,
             }
         } else if let hir::ExprKind::Path(ref qpath) = source.kind
             && let res = self.typeck_results().qpath_res(qpath, source.hir_id)
diff --git a/compiler/rustc_mir_build/src/thir/print.rs b/compiler/rustc_mir_build/src/thir/print.rs
index a507aeb76acd9..61317925d09e5 100644
--- a/compiler/rustc_mir_build/src/thir/print.rs
+++ b/compiler/rustc_mir_build/src/thir/print.rs
@@ -292,9 +292,14 @@ impl<'a, 'tcx> ThirPrinter<'a, 'tcx> {
                 self.print_expr(*source, depth_lvl + 2);
                 print_indented!(self, "}", depth_lvl);
             }
-            PointerCoercion { cast, source } => {
+            PointerCoercion { cast, is_from_as_cast, source } => {
                 print_indented!(self, "Pointer {", depth_lvl);
                 print_indented!(self, format!("cast: {:?}", cast), depth_lvl + 1);
+                print_indented!(
+                    self,
+                    format!("is_from_as_cast: {:?}", is_from_as_cast),
+                    depth_lvl + 1
+                );
                 print_indented!(self, "source:", depth_lvl + 1);
                 self.print_expr(*source, depth_lvl + 2);
                 print_indented!(self, "}", depth_lvl);
diff --git a/compiler/rustc_mir_transform/src/cleanup_post_borrowck.rs b/compiler/rustc_mir_transform/src/cleanup_post_borrowck.rs
index 5395e1b0e94d8..6a22a58470c95 100644
--- a/compiler/rustc_mir_transform/src/cleanup_post_borrowck.rs
+++ b/compiler/rustc_mir_transform/src/cleanup_post_borrowck.rs
@@ -42,6 +42,7 @@ impl<'tcx> crate::MirPass<'tcx> for CleanupPostBorrowck {
                             ref mut cast_kind @ CastKind::PointerCoercion(
                                 PointerCoercion::ArrayToPointer
                                 | PointerCoercion::MutToConstPointer,
+                                _,
                             ),
                             ..,
                         ),
diff --git a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
index 2026b7893159e..88dc8e74a8c29 100644
--- a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
+++ b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
@@ -189,7 +189,7 @@ impl<'tcx> ValueAnalysis<'tcx> for ConstAnalysis<'_, 'tcx> {
                 }
             }
             Rvalue::Cast(
-                CastKind::PointerCoercion(ty::adjustment::PointerCoercion::Unsize),
+                CastKind::PointerCoercion(ty::adjustment::PointerCoercion::Unsize, _),
                 operand,
                 _,
             ) => {
diff --git a/compiler/rustc_mir_transform/src/gvn.rs b/compiler/rustc_mir_transform/src/gvn.rs
index 4d44669fa3ec5..f735d08fca573 100644
--- a/compiler/rustc_mir_transform/src/gvn.rs
+++ b/compiler/rustc_mir_transform/src/gvn.rs
@@ -576,7 +576,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
                     }
                     value.offset(Size::ZERO, to, &self.ecx).ok()?
                 }
-                CastKind::PointerCoercion(ty::adjustment::PointerCoercion::Unsize) => {
+                CastKind::PointerCoercion(ty::adjustment::PointerCoercion::Unsize, _) => {
                     let src = self.evaluated[value].as_ref()?;
                     let to = self.ecx.layout_of(to).ok()?;
                     let dest = self.ecx.allocate(to, MemoryKind::Stack).ok()?;
@@ -593,7 +593,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
                     let ret = self.ecx.ptr_to_ptr(&src, to).ok()?;
                     ret.into()
                 }
-                CastKind::PointerCoercion(ty::adjustment::PointerCoercion::UnsafeFnPointer) => {
+                CastKind::PointerCoercion(ty::adjustment::PointerCoercion::UnsafeFnPointer, _) => {
                     let src = self.evaluated[value].as_ref()?;
                     let src = self.ecx.read_immediate(src).ok()?;
                     let to = self.ecx.layout_of(to).ok()?;
@@ -1138,7 +1138,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
             (
                 UnOp::PtrMetadata,
                 Value::Cast {
-                    kind: CastKind::PointerCoercion(ty::adjustment::PointerCoercion::Unsize),
+                    kind: CastKind::PointerCoercion(ty::adjustment::PointerCoercion::Unsize, _),
                     from,
                     to,
                     ..
@@ -1342,7 +1342,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
             return Some(value);
         }
 
-        if let CastKind::PointerCoercion(ReifyFnPointer | ClosureFnPointer(_)) = kind {
+        if let CastKind::PointerCoercion(ReifyFnPointer | ClosureFnPointer(_), _) = kind {
             // Each reification of a generic fn may get a different pointer.
             // Do not try to merge them.
             return self.new_opaque();
@@ -1429,7 +1429,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
 
         // We have an unsizing cast, which assigns the length to fat pointer metadata.
         if let Value::Cast { kind, from, to, .. } = self.get(inner)
-            && let CastKind::PointerCoercion(ty::adjustment::PointerCoercion::Unsize) = kind
+            && let CastKind::PointerCoercion(ty::adjustment::PointerCoercion::Unsize, _) = kind
             && let Some(from) = from.builtin_deref(true)
             && let ty::Array(_, len) = from.kind()
             && let Some(to) = to.builtin_deref(true)
diff --git a/compiler/rustc_mir_transform/src/mentioned_items.rs b/compiler/rustc_mir_transform/src/mentioned_items.rs
index 9f9b39b02d39e..cf5c5f85a9ff6 100644
--- a/compiler/rustc_mir_transform/src/mentioned_items.rs
+++ b/compiler/rustc_mir_transform/src/mentioned_items.rs
@@ -70,8 +70,8 @@ impl<'tcx> Visitor<'tcx> for MentionedItemsVisitor<'_, 'tcx> {
         match *rvalue {
             // We need to detect unsizing casts that required vtables.
             mir::Rvalue::Cast(
-                mir::CastKind::PointerCoercion(PointerCoercion::Unsize)
-                | mir::CastKind::PointerCoercion(PointerCoercion::DynStar),
+                mir::CastKind::PointerCoercion(PointerCoercion::Unsize, _)
+                | mir::CastKind::PointerCoercion(PointerCoercion::DynStar, _),
                 ref operand,
                 target_ty,
             ) => {
@@ -96,7 +96,7 @@ impl<'tcx> Visitor<'tcx> for MentionedItemsVisitor<'_, 'tcx> {
             }
             // Similarly, record closures that are turned into function pointers.
             mir::Rvalue::Cast(
-                mir::CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_)),
+                mir::CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_), _),
                 ref operand,
                 _,
             ) => {
@@ -106,7 +106,7 @@ impl<'tcx> Visitor<'tcx> for MentionedItemsVisitor<'_, 'tcx> {
             }
             // And finally, function pointer reification casts.
             mir::Rvalue::Cast(
-                mir::CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer),
+                mir::CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer, _),
                 ref operand,
                 _,
             ) => {
diff --git a/compiler/rustc_mir_transform/src/shim/async_destructor_ctor.rs b/compiler/rustc_mir_transform/src/shim/async_destructor_ctor.rs
index c206252c15aa4..71723f040b3b6 100644
--- a/compiler/rustc_mir_transform/src/shim/async_destructor_ctor.rs
+++ b/compiler/rustc_mir_transform/src/shim/async_destructor_ctor.rs
@@ -7,9 +7,10 @@ use rustc_hir::def_id::DefId;
 use rustc_hir::lang_items::LangItem;
 use rustc_index::{Idx, IndexVec};
 use rustc_middle::mir::{
-    BasicBlock, BasicBlockData, Body, CallSource, CastKind, Const, ConstOperand, ConstValue, Local,
-    LocalDecl, MirSource, Operand, Place, PlaceElem, RETURN_PLACE, Rvalue, SourceInfo, Statement,
-    StatementKind, Terminator, TerminatorKind, UnwindAction, UnwindTerminateReason,
+    BasicBlock, BasicBlockData, Body, CallSource, CastKind, CoercionSource, Const, ConstOperand,
+    ConstValue, Local, LocalDecl, MirSource, Operand, Place, PlaceElem, RETURN_PLACE, Rvalue,
+    SourceInfo, Statement, StatementKind, Terminator, TerminatorKind, UnwindAction,
+    UnwindTerminateReason,
 };
 use rustc_middle::ty::adjustment::PointerCoercion;
 use rustc_middle::ty::util::{AsyncDropGlueMorphology, Discr};
@@ -329,7 +330,7 @@ impl<'tcx> AsyncDestructorCtorShimBuilder<'tcx> {
     fn put_array_as_slice(&mut self, elem_ty: Ty<'tcx>) {
         let slice_ptr_ty = Ty::new_mut_ptr(self.tcx, Ty::new_slice(self.tcx, elem_ty));
         self.put_temp_rvalue(Rvalue::Cast(
-            CastKind::PointerCoercion(PointerCoercion::Unsize),
+            CastKind::PointerCoercion(PointerCoercion::Unsize, CoercionSource::Implicit),
             Operand::Copy(Self::SELF_PTR.into()),
             slice_ptr_ty,
         ))
diff --git a/compiler/rustc_mir_transform/src/validate.rs b/compiler/rustc_mir_transform/src/validate.rs
index 2b6498409d046..eda0b8c75f322 100644
--- a/compiler/rustc_mir_transform/src/validate.rs
+++ b/compiler/rustc_mir_transform/src/validate.rs
@@ -1130,7 +1130,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                 match kind {
                     // FIXME: Add Checks for these
                     CastKind::PointerWithExposedProvenance | CastKind::PointerExposeProvenance => {}
-                    CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer) => {
+                    CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer, _) => {
                         // FIXME: check signature compatibility.
                         check_kinds!(
                             op_ty,
@@ -1143,7 +1143,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                             ty::FnPtr(..)
                         );
                     }
-                    CastKind::PointerCoercion(PointerCoercion::UnsafeFnPointer) => {
+                    CastKind::PointerCoercion(PointerCoercion::UnsafeFnPointer, _) => {
                         // FIXME: check safety and signature compatibility.
                         check_kinds!(
                             op_ty,
@@ -1156,7 +1156,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                             ty::FnPtr(..)
                         );
                     }
-                    CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(..)) => {
+                    CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(..), _) => {
                         // FIXME: check safety, captures, and signature compatibility.
                         check_kinds!(
                             op_ty,
@@ -1169,7 +1169,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                             ty::FnPtr(..)
                         );
                     }
-                    CastKind::PointerCoercion(PointerCoercion::MutToConstPointer) => {
+                    CastKind::PointerCoercion(PointerCoercion::MutToConstPointer, _) => {
                         // FIXME: check same pointee?
                         check_kinds!(
                             op_ty,
@@ -1185,7 +1185,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                             self.fail(location, format!("After borrowck, MIR disallows {kind:?}"));
                         }
                     }
-                    CastKind::PointerCoercion(PointerCoercion::ArrayToPointer) => {
+                    CastKind::PointerCoercion(PointerCoercion::ArrayToPointer, _) => {
                         // FIXME: Check pointee types
                         check_kinds!(
                             op_ty,
@@ -1201,11 +1201,11 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                             self.fail(location, format!("After borrowck, MIR disallows {kind:?}"));
                         }
                     }
-                    CastKind::PointerCoercion(PointerCoercion::Unsize) => {
+                    CastKind::PointerCoercion(PointerCoercion::Unsize, _) => {
                         // This is used for all `CoerceUnsized` types,
                         // not just pointers/references, so is hard to check.
                     }
-                    CastKind::PointerCoercion(PointerCoercion::DynStar) => {
+                    CastKind::PointerCoercion(PointerCoercion::DynStar, _) => {
                         // FIXME(dyn-star): make sure nothing needs to be done here.
                     }
                     CastKind::IntToInt | CastKind::IntToFloat => {
diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs
index 986d0030a2406..fd3ae4435a683 100644
--- a/compiler/rustc_monomorphize/src/collector.rs
+++ b/compiler/rustc_monomorphize/src/collector.rs
@@ -665,8 +665,8 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirUsedCollector<'a, 'tcx> {
             // have to instantiate all methods of the trait being cast to, so we
             // can build the appropriate vtable.
             mir::Rvalue::Cast(
-                mir::CastKind::PointerCoercion(PointerCoercion::Unsize)
-                | mir::CastKind::PointerCoercion(PointerCoercion::DynStar),
+                mir::CastKind::PointerCoercion(PointerCoercion::Unsize, _)
+                | mir::CastKind::PointerCoercion(PointerCoercion::DynStar, _),
                 ref operand,
                 target_ty,
             ) => {
@@ -694,7 +694,7 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirUsedCollector<'a, 'tcx> {
                 }
             }
             mir::Rvalue::Cast(
-                mir::CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer),
+                mir::CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer, _),
                 ref operand,
                 _,
             ) => {
@@ -705,7 +705,7 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirUsedCollector<'a, 'tcx> {
                 visit_fn_use(self.tcx, fn_ty, false, span, self.used_items);
             }
             mir::Rvalue::Cast(
-                mir::CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_)),
+                mir::CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_), _),
                 ref operand,
                 _,
             ) => {
diff --git a/compiler/rustc_smir/src/rustc_smir/convert/mir.rs b/compiler/rustc_smir/src/rustc_smir/convert/mir.rs
index e702503724240..0dbbc338e738b 100644
--- a/compiler/rustc_smir/src/rustc_smir/convert/mir.rs
+++ b/compiler/rustc_smir/src/rustc_smir/convert/mir.rs
@@ -286,8 +286,8 @@ impl<'tcx> Stable<'tcx> for mir::CastKind {
         match self {
             PointerExposeProvenance => stable_mir::mir::CastKind::PointerExposeAddress,
             PointerWithExposedProvenance => stable_mir::mir::CastKind::PointerWithExposedProvenance,
-            PointerCoercion(PointerCoercion::DynStar) => stable_mir::mir::CastKind::DynStar,
-            PointerCoercion(c) => stable_mir::mir::CastKind::PointerCoercion(c.stable(tables)),
+            PointerCoercion(PointerCoercion::DynStar, _) => stable_mir::mir::CastKind::DynStar,
+            PointerCoercion(c, _) => stable_mir::mir::CastKind::PointerCoercion(c.stable(tables)),
             IntToInt => stable_mir::mir::CastKind::IntToInt,
             FloatToInt => stable_mir::mir::CastKind::FloatToInt,
             FloatToFloat => stable_mir::mir::CastKind::FloatToFloat,
diff --git a/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs b/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
index 6434c2f42cfb9..ce1895b7fb19b 100644
--- a/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
+++ b/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
@@ -123,7 +123,7 @@ fn check_rvalue<'tcx>(
             | CastKind::FloatToFloat
             | CastKind::FnPtrToPtr
             | CastKind::PtrToPtr
-            | CastKind::PointerCoercion(PointerCoercion::MutToConstPointer | PointerCoercion::ArrayToPointer),
+            | CastKind::PointerCoercion(PointerCoercion::MutToConstPointer | PointerCoercion::ArrayToPointer, _),
             operand,
             _,
         ) => check_operand(tcx, operand, span, body, msrv),
@@ -131,12 +131,12 @@ fn check_rvalue<'tcx>(
             CastKind::PointerCoercion(
                 PointerCoercion::UnsafeFnPointer
                 | PointerCoercion::ClosureFnPointer(_)
-                | PointerCoercion::ReifyFnPointer,
+                | PointerCoercion::ReifyFnPointer, _
             ),
             _,
             _,
         ) => Err((span, "function pointer casts are not allowed in const fn".into())),
-        Rvalue::Cast(CastKind::PointerCoercion(PointerCoercion::Unsize), op, cast_ty) => {
+        Rvalue::Cast(CastKind::PointerCoercion(PointerCoercion::Unsize, _), op, cast_ty) => {
             let Some(pointee_ty) = cast_ty.builtin_deref(true) else {
                 // We cannot allow this for now.
                 return Err((span, "unsizing casts are only allowed for references right now".into()));
@@ -154,7 +154,7 @@ fn check_rvalue<'tcx>(
         Rvalue::Cast(CastKind::PointerExposeProvenance, _, _) => {
             Err((span, "casting pointers to ints is unstable in const fn".into()))
         },
-        Rvalue::Cast(CastKind::PointerCoercion(PointerCoercion::DynStar), _, _) => {
+        Rvalue::Cast(CastKind::PointerCoercion(PointerCoercion::DynStar, _), _, _) => {
             // FIXME(dyn-star)
             unimplemented!()
         },
diff --git a/src/tools/miri/tests/fail/dyn-upcast-trait-mismatch.stderr b/src/tools/miri/tests/fail/dyn-upcast-trait-mismatch.stderr
index b40f83e86541a..d0fd0e6fcc144 100644
--- a/src/tools/miri/tests/fail/dyn-upcast-trait-mismatch.stderr
+++ b/src/tools/miri/tests/fail/dyn-upcast-trait-mismatch.stderr
@@ -2,7 +2,7 @@ error: Undefined Behavior: using vtable for `Baz` but `Bar` was expected
   --> tests/fail/dyn-upcast-trait-mismatch.rs:LL:CC
    |
 LL |         let _err = baz_fake as *const dyn Foo;
-   |                    ^^^^^^^^ using vtable for `Baz` but `Bar` was expected
+   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^ using vtable for `Baz` but `Bar` was expected
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
diff --git a/tests/mir-opt/address_of.address_of_reborrow.SimplifyCfg-initial.after.mir b/tests/mir-opt/address_of.address_of_reborrow.SimplifyCfg-initial.after.mir
index edf62a1e17398..ae445ad9b915b 100644
--- a/tests/mir-opt/address_of.address_of_reborrow.SimplifyCfg-initial.after.mir
+++ b/tests/mir-opt/address_of.address_of_reborrow.SimplifyCfg-initial.after.mir
@@ -150,7 +150,7 @@ fn address_of_reborrow() -> () {
         StorageLive(_9);
         StorageLive(_10);
         _10 = &raw const (*_1);
-        _9 = move _10 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+        _9 = move _10 as *const dyn std::marker::Send (PointerCoercion(Unsize, AsCast));
         StorageDead(_10);
         AscribeUserType(_9, o, UserTypeProjection { base: UserType(1), projs: [] });
         _8 = copy _9;
@@ -159,13 +159,13 @@ fn address_of_reborrow() -> () {
         StorageLive(_11);
         StorageLive(_12);
         _12 = &raw const (*_1);
-        _11 = move _12 as *const [i32] (PointerCoercion(Unsize));
+        _11 = move _12 as *const [i32] (PointerCoercion(Unsize, AsCast));
         StorageDead(_12);
         StorageDead(_11);
         StorageLive(_13);
         StorageLive(_14);
         _14 = &raw const (*_1);
-        _13 = move _14 as *const i32 (PointerCoercion(ArrayToPointer));
+        _13 = move _14 as *const i32 (PointerCoercion(ArrayToPointer, AsCast));
         StorageDead(_14);
         StorageDead(_13);
         StorageLive(_15);
@@ -179,14 +179,14 @@ fn address_of_reborrow() -> () {
         StorageLive(_17);
         StorageLive(_18);
         _18 = &raw const (*_1);
-        _17 = move _18 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+        _17 = move _18 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
         StorageDead(_18);
         FakeRead(ForLet(None), _17);
         AscribeUserType(_17, o, UserTypeProjection { base: UserType(7), projs: [] });
         StorageLive(_19);
         StorageLive(_20);
         _20 = &raw const (*_1);
-        _19 = move _20 as *const [i32] (PointerCoercion(Unsize));
+        _19 = move _20 as *const [i32] (PointerCoercion(Unsize, Implicit));
         StorageDead(_20);
         FakeRead(ForLet(None), _19);
         AscribeUserType(_19, o, UserTypeProjection { base: UserType(9), projs: [] });
@@ -204,7 +204,7 @@ fn address_of_reborrow() -> () {
         StorageLive(_25);
         StorageLive(_26);
         _26 = &raw const (*_3);
-        _25 = move _26 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+        _25 = move _26 as *const dyn std::marker::Send (PointerCoercion(Unsize, AsCast));
         StorageDead(_26);
         AscribeUserType(_25, o, UserTypeProjection { base: UserType(11), projs: [] });
         _24 = copy _25;
@@ -213,7 +213,7 @@ fn address_of_reborrow() -> () {
         StorageLive(_27);
         StorageLive(_28);
         _28 = &raw const (*_3);
-        _27 = move _28 as *const [i32] (PointerCoercion(Unsize));
+        _27 = move _28 as *const [i32] (PointerCoercion(Unsize, AsCast));
         StorageDead(_28);
         StorageDead(_27);
         StorageLive(_29);
@@ -227,14 +227,14 @@ fn address_of_reborrow() -> () {
         StorageLive(_31);
         StorageLive(_32);
         _32 = &raw const (*_3);
-        _31 = move _32 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+        _31 = move _32 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
         StorageDead(_32);
         FakeRead(ForLet(None), _31);
         AscribeUserType(_31, o, UserTypeProjection { base: UserType(17), projs: [] });
         StorageLive(_33);
         StorageLive(_34);
         _34 = &raw const (*_3);
-        _33 = move _34 as *const [i32] (PointerCoercion(Unsize));
+        _33 = move _34 as *const [i32] (PointerCoercion(Unsize, Implicit));
         StorageDead(_34);
         FakeRead(ForLet(None), _33);
         AscribeUserType(_33, o, UserTypeProjection { base: UserType(19), projs: [] });
@@ -252,7 +252,7 @@ fn address_of_reborrow() -> () {
         StorageLive(_39);
         StorageLive(_40);
         _40 = &raw mut (*_3);
-        _39 = move _40 as *mut dyn std::marker::Send (PointerCoercion(Unsize));
+        _39 = move _40 as *mut dyn std::marker::Send (PointerCoercion(Unsize, AsCast));
         StorageDead(_40);
         AscribeUserType(_39, o, UserTypeProjection { base: UserType(21), projs: [] });
         _38 = copy _39;
@@ -261,7 +261,7 @@ fn address_of_reborrow() -> () {
         StorageLive(_41);
         StorageLive(_42);
         _42 = &raw mut (*_3);
-        _41 = move _42 as *mut [i32] (PointerCoercion(Unsize));
+        _41 = move _42 as *mut [i32] (PointerCoercion(Unsize, AsCast));
         StorageDead(_42);
         StorageDead(_41);
         StorageLive(_43);
@@ -275,14 +275,14 @@ fn address_of_reborrow() -> () {
         StorageLive(_45);
         StorageLive(_46);
         _46 = &raw mut (*_3);
-        _45 = move _46 as *mut dyn std::marker::Send (PointerCoercion(Unsize));
+        _45 = move _46 as *mut dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
         StorageDead(_46);
         FakeRead(ForLet(None), _45);
         AscribeUserType(_45, o, UserTypeProjection { base: UserType(27), projs: [] });
         StorageLive(_47);
         StorageLive(_48);
         _48 = &raw mut (*_3);
-        _47 = move _48 as *mut [i32] (PointerCoercion(Unsize));
+        _47 = move _48 as *mut [i32] (PointerCoercion(Unsize, Implicit));
         StorageDead(_48);
         FakeRead(ForLet(None), _47);
         AscribeUserType(_47, o, UserTypeProjection { base: UserType(29), projs: [] });
diff --git a/tests/mir-opt/build_correct_coerce.main.built.after.mir b/tests/mir-opt/build_correct_coerce.main.built.after.mir
index 061174d69bb05..583a5ecd22702 100644
--- a/tests/mir-opt/build_correct_coerce.main.built.after.mir
+++ b/tests/mir-opt/build_correct_coerce.main.built.after.mir
@@ -9,7 +9,7 @@ fn main() -> () {
 
     bb0: {
         StorageLive(_1);
-        _1 = foo as for<'a> fn(&'a (), &'a ()) (PointerCoercion(ReifyFnPointer));
+        _1 = foo as for<'a> fn(&'a (), &'a ()) (PointerCoercion(ReifyFnPointer, AsCast));
         FakeRead(ForLet(None), _1);
         _0 = const ();
         StorageDead(_1);
diff --git a/tests/mir-opt/building/receiver_ptr_mutability.main.built.after.mir b/tests/mir-opt/building/receiver_ptr_mutability.main.built.after.mir
index 296d71a319d1b..be972b62cbd31 100644
--- a/tests/mir-opt/building/receiver_ptr_mutability.main.built.after.mir
+++ b/tests/mir-opt/building/receiver_ptr_mutability.main.built.after.mir
@@ -39,7 +39,7 @@ fn main() -> () {
         StorageLive(_3);
         StorageLive(_4);
         _4 = copy _1;
-        _3 = move _4 as *const Test (PointerCoercion(MutToConstPointer));
+        _3 = move _4 as *const Test (PointerCoercion(MutToConstPointer, Implicit));
         StorageDead(_4);
         _2 = Test::x(move _3) -> [return: bb2, unwind: bb4];
     }
@@ -64,7 +64,7 @@ fn main() -> () {
         StorageLive(_11);
         StorageLive(_12);
         _12 = copy (*(*(*(*_5))));
-        _11 = move _12 as *const Test (PointerCoercion(MutToConstPointer));
+        _11 = move _12 as *const Test (PointerCoercion(MutToConstPointer, Implicit));
         StorageDead(_12);
         _10 = Test::x(move _11) -> [return: bb3, unwind: bb4];
     }
diff --git a/tests/mir-opt/building/storage_live_dead_in_statics.XXX.built.after.mir b/tests/mir-opt/building/storage_live_dead_in_statics.XXX.built.after.mir
index 683f63065f76b..73ead005f8c62 100644
--- a/tests/mir-opt/building/storage_live_dead_in_statics.XXX.built.after.mir
+++ b/tests/mir-opt/building/storage_live_dead_in_statics.XXX.built.after.mir
@@ -187,7 +187,7 @@ static XXX: &Foo = {
         StorageDead(_7);
         _5 = &_6;
         _4 = &(*_5);
-        _3 = move _4 as &[(u32, u32)] (PointerCoercion(Unsize));
+        _3 = move _4 as &[(u32, u32)] (PointerCoercion(Unsize, Implicit));
         StorageDead(_4);
         _2 = Foo { tup: const "hi", data: move _3 };
         StorageDead(_3);
diff --git a/tests/mir-opt/const_promotion_extern_static.BAR.PromoteTemps.diff b/tests/mir-opt/const_promotion_extern_static.BAR.PromoteTemps.diff
index f412048b6ec7e..487f68a8d4dfe 100644
--- a/tests/mir-opt/const_promotion_extern_static.BAR.PromoteTemps.diff
+++ b/tests/mir-opt/const_promotion_extern_static.BAR.PromoteTemps.diff
@@ -22,7 +22,7 @@
 -         _2 = &_3;
 +         _6 = const BAR::promoted[0];
 +         _2 = &(*_6);
-          _1 = move _2 as &[&i32] (PointerCoercion(Unsize));
+          _1 = move _2 as &[&i32] (PointerCoercion(Unsize, Implicit));
 -         StorageDead(_4);
           StorageDead(_2);
           _0 = core::slice::<impl [&i32]>::as_ptr(move _1) -> [return: bb1, unwind: bb2];
diff --git a/tests/mir-opt/const_promotion_extern_static.FOO.PromoteTemps.diff b/tests/mir-opt/const_promotion_extern_static.FOO.PromoteTemps.diff
index bfefd2b8c95c6..0e4eed2c028d0 100644
--- a/tests/mir-opt/const_promotion_extern_static.FOO.PromoteTemps.diff
+++ b/tests/mir-opt/const_promotion_extern_static.FOO.PromoteTemps.diff
@@ -22,7 +22,7 @@
 -         _2 = &_3;
 +         _6 = const FOO::promoted[0];
 +         _2 = &(*_6);
-          _1 = move _2 as &[&i32] (PointerCoercion(Unsize));
+          _1 = move _2 as &[&i32] (PointerCoercion(Unsize, Implicit));
 -         StorageDead(_4);
           StorageDead(_2);
           _0 = core::slice::<impl [&i32]>::as_ptr(move _1) -> [return: bb1, unwind: bb2];
diff --git a/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.32bit.panic-abort.diff b/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.32bit.panic-abort.diff
index 52aa4da49efaf..15d3014036713 100644
--- a/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.32bit.panic-abort.diff
+++ b/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.32bit.panic-abort.diff
@@ -26,7 +26,7 @@
           _9 = const main::promoted[0];
           _3 = &(*_9);
           _2 = &raw const (*_3);
-          _1 = move _2 as *const [i32] (PointerCoercion(Unsize));
+          _1 = move _2 as *const [i32] (PointerCoercion(Unsize, Implicit));
           StorageDead(_2);
           StorageDead(_3);
           StorageLive(_5);
diff --git a/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.32bit.panic-unwind.diff b/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.32bit.panic-unwind.diff
index 242ff0e664f1d..dd411d84f9fbe 100644
--- a/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.32bit.panic-unwind.diff
+++ b/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.32bit.panic-unwind.diff
@@ -26,7 +26,7 @@
           _9 = const main::promoted[0];
           _3 = &(*_9);
           _2 = &raw const (*_3);
-          _1 = move _2 as *const [i32] (PointerCoercion(Unsize));
+          _1 = move _2 as *const [i32] (PointerCoercion(Unsize, Implicit));
           StorageDead(_2);
           StorageDead(_3);
           StorageLive(_5);
diff --git a/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.64bit.panic-abort.diff b/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.64bit.panic-abort.diff
index 52aa4da49efaf..15d3014036713 100644
--- a/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.64bit.panic-abort.diff
+++ b/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.64bit.panic-abort.diff
@@ -26,7 +26,7 @@
           _9 = const main::promoted[0];
           _3 = &(*_9);
           _2 = &raw const (*_3);
-          _1 = move _2 as *const [i32] (PointerCoercion(Unsize));
+          _1 = move _2 as *const [i32] (PointerCoercion(Unsize, Implicit));
           StorageDead(_2);
           StorageDead(_3);
           StorageLive(_5);
diff --git a/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.64bit.panic-unwind.diff b/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.64bit.panic-unwind.diff
index 242ff0e664f1d..dd411d84f9fbe 100644
--- a/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.64bit.panic-unwind.diff
+++ b/tests/mir-opt/const_prop/bad_op_unsafe_oob_for_slices.main.GVN.64bit.panic-unwind.diff
@@ -26,7 +26,7 @@
           _9 = const main::promoted[0];
           _3 = &(*_9);
           _2 = &raw const (*_3);
-          _1 = move _2 as *const [i32] (PointerCoercion(Unsize));
+          _1 = move _2 as *const [i32] (PointerCoercion(Unsize, Implicit));
           StorageDead(_2);
           StorageDead(_3);
           StorageLive(_5);
diff --git a/tests/mir-opt/const_prop/reify_fn_ptr.main.GVN.diff b/tests/mir-opt/const_prop/reify_fn_ptr.main.GVN.diff
index e5786bcf701ef..50a17326c2aae 100644
--- a/tests/mir-opt/const_prop/reify_fn_ptr.main.GVN.diff
+++ b/tests/mir-opt/const_prop/reify_fn_ptr.main.GVN.diff
@@ -13,7 +13,7 @@
           StorageLive(_1);
           StorageLive(_2);
           StorageLive(_3);
-          _3 = main as fn() (PointerCoercion(ReifyFnPointer));
+          _3 = main as fn() (PointerCoercion(ReifyFnPointer, AsCast));
           _2 = move _3 as usize (PointerExposeProvenance);
           StorageDead(_3);
           _1 = move _2 as *const fn() (PointerWithExposedProvenance);
diff --git a/tests/mir-opt/const_prop/reify_fn_ptr.rs b/tests/mir-opt/const_prop/reify_fn_ptr.rs
index ffce4e97f5de1..d56f21e586aa8 100644
--- a/tests/mir-opt/const_prop/reify_fn_ptr.rs
+++ b/tests/mir-opt/const_prop/reify_fn_ptr.rs
@@ -3,7 +3,7 @@
 
 fn main() {
     // CHECK-LABEL: fn main(
-    // CHECK: [[ptr:_.*]] = main as fn() (PointerCoercion(ReifyFnPointer));
+    // CHECK: [[ptr:_.*]] = main as fn() (PointerCoercion(ReifyFnPointer, AsCast));
     // CHECK: [[addr:_.*]] = move [[ptr]] as usize (PointerExposeProvenance);
     // CHECK: [[back:_.*]] = move [[addr]] as *const fn() (PointerWithExposedProvenance);
     let _ = main as usize as *const fn();
diff --git a/tests/mir-opt/const_prop/slice_len.main.GVN.32bit.panic-abort.diff b/tests/mir-opt/const_prop/slice_len.main.GVN.32bit.panic-abort.diff
index e834a5802c33f..41ce94eda7517 100644
--- a/tests/mir-opt/const_prop/slice_len.main.GVN.32bit.panic-abort.diff
+++ b/tests/mir-opt/const_prop/slice_len.main.GVN.32bit.panic-abort.diff
@@ -24,9 +24,9 @@
           _9 = const main::promoted[0];
           _4 = copy _9;
 -         _3 = copy _4;
--         _2 = move _3 as &[u32] (PointerCoercion(Unsize));
+-         _2 = move _3 as &[u32] (PointerCoercion(Unsize, AsCast));
 +         _3 = copy _9;
-+         _2 = copy _9 as &[u32] (PointerCoercion(Unsize));
++         _2 = copy _9 as &[u32] (PointerCoercion(Unsize, AsCast));
           StorageDead(_3);
           StorageLive(_6);
           _6 = const 1_usize;
diff --git a/tests/mir-opt/const_prop/slice_len.main.GVN.32bit.panic-unwind.diff b/tests/mir-opt/const_prop/slice_len.main.GVN.32bit.panic-unwind.diff
index 55ffc50180569..8cced96cd4331 100644
--- a/tests/mir-opt/const_prop/slice_len.main.GVN.32bit.panic-unwind.diff
+++ b/tests/mir-opt/const_prop/slice_len.main.GVN.32bit.panic-unwind.diff
@@ -24,9 +24,9 @@
           _9 = const main::promoted[0];
           _4 = copy _9;
 -         _3 = copy _4;
--         _2 = move _3 as &[u32] (PointerCoercion(Unsize));
+-         _2 = move _3 as &[u32] (PointerCoercion(Unsize, AsCast));
 +         _3 = copy _9;
-+         _2 = copy _9 as &[u32] (PointerCoercion(Unsize));
++         _2 = copy _9 as &[u32] (PointerCoercion(Unsize, AsCast));
           StorageDead(_3);
           StorageLive(_6);
           _6 = const 1_usize;
diff --git a/tests/mir-opt/const_prop/slice_len.main.GVN.64bit.panic-abort.diff b/tests/mir-opt/const_prop/slice_len.main.GVN.64bit.panic-abort.diff
index e834a5802c33f..41ce94eda7517 100644
--- a/tests/mir-opt/const_prop/slice_len.main.GVN.64bit.panic-abort.diff
+++ b/tests/mir-opt/const_prop/slice_len.main.GVN.64bit.panic-abort.diff
@@ -24,9 +24,9 @@
           _9 = const main::promoted[0];
           _4 = copy _9;
 -         _3 = copy _4;
--         _2 = move _3 as &[u32] (PointerCoercion(Unsize));
+-         _2 = move _3 as &[u32] (PointerCoercion(Unsize, AsCast));
 +         _3 = copy _9;
-+         _2 = copy _9 as &[u32] (PointerCoercion(Unsize));
++         _2 = copy _9 as &[u32] (PointerCoercion(Unsize, AsCast));
           StorageDead(_3);
           StorageLive(_6);
           _6 = const 1_usize;
diff --git a/tests/mir-opt/const_prop/slice_len.main.GVN.64bit.panic-unwind.diff b/tests/mir-opt/const_prop/slice_len.main.GVN.64bit.panic-unwind.diff
index 55ffc50180569..8cced96cd4331 100644
--- a/tests/mir-opt/const_prop/slice_len.main.GVN.64bit.panic-unwind.diff
+++ b/tests/mir-opt/const_prop/slice_len.main.GVN.64bit.panic-unwind.diff
@@ -24,9 +24,9 @@
           _9 = const main::promoted[0];
           _4 = copy _9;
 -         _3 = copy _4;
--         _2 = move _3 as &[u32] (PointerCoercion(Unsize));
+-         _2 = move _3 as &[u32] (PointerCoercion(Unsize, AsCast));
 +         _3 = copy _9;
-+         _2 = copy _9 as &[u32] (PointerCoercion(Unsize));
++         _2 = copy _9 as &[u32] (PointerCoercion(Unsize, AsCast));
           StorageDead(_3);
           StorageLive(_6);
           _6 = const 1_usize;
diff --git a/tests/mir-opt/const_prop/slice_len.rs b/tests/mir-opt/const_prop/slice_len.rs
index 46604cfe1e091..ebd3c9e792dca 100644
--- a/tests/mir-opt/const_prop/slice_len.rs
+++ b/tests/mir-opt/const_prop/slice_len.rs
@@ -7,7 +7,7 @@
 fn main() {
     // CHECK-LABEL: fn main(
     // CHECK: debug a => [[a:_.*]];
-    // CHECK: [[slice:_.*]] = copy {{.*}} as &[u32] (PointerCoercion(Unsize));
+    // CHECK: [[slice:_.*]] = copy {{.*}} as &[u32] (PointerCoercion(Unsize, AsCast));
     // CHECK: assert(const true,
     // CHECK: [[a]] = const 2_u32;
     let a = (&[1u32, 2, 3] as &[u32])[1];
diff --git a/tests/mir-opt/copy-prop/issue_107511.main.CopyProp.panic-abort.diff b/tests/mir-opt/copy-prop/issue_107511.main.CopyProp.panic-abort.diff
index f4411886f9a7a..6d967257df1f5 100644
--- a/tests/mir-opt/copy-prop/issue_107511.main.CopyProp.panic-abort.diff
+++ b/tests/mir-opt/copy-prop/issue_107511.main.CopyProp.panic-abort.diff
@@ -47,7 +47,7 @@
           StorageLive(_6);
           StorageLive(_7);
           _7 = &_2;
-          _6 = move _7 as &[i32] (PointerCoercion(Unsize));
+          _6 = move _7 as &[i32] (PointerCoercion(Unsize, Implicit));
           StorageDead(_7);
           _5 = core::slice::<impl [i32]>::len(move _6) -> [return: bb1, unwind unreachable];
       }
diff --git a/tests/mir-opt/copy-prop/issue_107511.main.CopyProp.panic-unwind.diff b/tests/mir-opt/copy-prop/issue_107511.main.CopyProp.panic-unwind.diff
index 833588aa4e920..3580c87c46995 100644
--- a/tests/mir-opt/copy-prop/issue_107511.main.CopyProp.panic-unwind.diff
+++ b/tests/mir-opt/copy-prop/issue_107511.main.CopyProp.panic-unwind.diff
@@ -47,7 +47,7 @@
           StorageLive(_6);
           StorageLive(_7);
           _7 = &_2;
-          _6 = move _7 as &[i32] (PointerCoercion(Unsize));
+          _6 = move _7 as &[i32] (PointerCoercion(Unsize, Implicit));
           StorageDead(_7);
           _5 = core::slice::<impl [i32]>::len(move _6) -> [return: bb1, unwind continue];
       }
diff --git a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.32bit.panic-abort.diff b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.32bit.panic-abort.diff
index c7870a7902b98..e62fcb66e3a6d 100644
--- a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.32bit.panic-abort.diff
+++ b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.32bit.panic-abort.diff
@@ -89,7 +89,7 @@
 -         _4 = Unique::<[bool; 0]> { pointer: move _5, _marker: const PhantomData::<[bool; 0]> };
 +         _4 = const Unique::<[bool; 0]> {{ pointer: NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }}, _marker: PhantomData::<[bool; 0]> }};
           StorageDead(_5);
--         _3 = move _4 as std::ptr::Unique<[bool]> (PointerCoercion(Unsize));
+-         _3 = move _4 as std::ptr::Unique<[bool]> (PointerCoercion(Unsize, Implicit));
 +         _3 = const Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: ALLOC0, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }};
           StorageDead(_4);
 -         _2 = Box::<[bool]>(copy _3, const std::alloc::Global);
diff --git a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.32bit.panic-unwind.diff b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.32bit.panic-unwind.diff
index f5de7a361bc10..8183abd315ae5 100644
--- a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.32bit.panic-unwind.diff
+++ b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.32bit.panic-unwind.diff
@@ -93,7 +93,7 @@
 -         _4 = Unique::<[bool; 0]> { pointer: move _5, _marker: const PhantomData::<[bool; 0]> };
 +         _4 = const Unique::<[bool; 0]> {{ pointer: NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }}, _marker: PhantomData::<[bool; 0]> }};
           StorageDead(_5);
--         _3 = move _4 as std::ptr::Unique<[bool]> (PointerCoercion(Unsize));
+-         _3 = move _4 as std::ptr::Unique<[bool]> (PointerCoercion(Unsize, Implicit));
 +         _3 = const Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: ALLOC0, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }};
           StorageDead(_4);
 -         _2 = Box::<[bool]>(copy _3, const std::alloc::Global);
diff --git a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.64bit.panic-abort.diff b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.64bit.panic-abort.diff
index 3b0bc6377da62..4fa6ef29e0697 100644
--- a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.64bit.panic-abort.diff
+++ b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.64bit.panic-abort.diff
@@ -89,7 +89,7 @@
 -         _4 = Unique::<[bool; 0]> { pointer: move _5, _marker: const PhantomData::<[bool; 0]> };
 +         _4 = const Unique::<[bool; 0]> {{ pointer: NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }}, _marker: PhantomData::<[bool; 0]> }};
           StorageDead(_5);
--         _3 = move _4 as std::ptr::Unique<[bool]> (PointerCoercion(Unsize));
+-         _3 = move _4 as std::ptr::Unique<[bool]> (PointerCoercion(Unsize, Implicit));
 +         _3 = const Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: ALLOC0, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }};
           StorageDead(_4);
 -         _2 = Box::<[bool]>(copy _3, const std::alloc::Global);
diff --git a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.64bit.panic-unwind.diff b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.64bit.panic-unwind.diff
index 5dd7ad9a11773..753292045632f 100644
--- a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.64bit.panic-unwind.diff
+++ b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.64bit.panic-unwind.diff
@@ -93,7 +93,7 @@
 -         _4 = Unique::<[bool; 0]> { pointer: move _5, _marker: const PhantomData::<[bool; 0]> };
 +         _4 = const Unique::<[bool; 0]> {{ pointer: NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }}, _marker: PhantomData::<[bool; 0]> }};
           StorageDead(_5);
--         _3 = move _4 as std::ptr::Unique<[bool]> (PointerCoercion(Unsize));
+-         _3 = move _4 as std::ptr::Unique<[bool]> (PointerCoercion(Unsize, Implicit));
 +         _3 = const Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: ALLOC0, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }};
           StorageDead(_4);
 -         _2 = Box::<[bool]>(copy _3, const std::alloc::Global);
diff --git a/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.32bit.panic-abort.diff b/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.32bit.panic-abort.diff
index 40632db667a8d..e71992316dcf4 100644
--- a/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.32bit.panic-abort.diff
+++ b/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.32bit.panic-abort.diff
@@ -32,7 +32,7 @@
           _14 = const main::promoted[0];
           _4 = copy _14;
           _3 = copy _4;
-          _2 = move _3 as &[u32] (PointerCoercion(Unsize));
+          _2 = move _3 as &[u32] (PointerCoercion(Unsize, AsCast));
           StorageDead(_3);
           StorageLive(_6);
           _6 = const 1_usize;
diff --git a/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.32bit.panic-unwind.diff b/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.32bit.panic-unwind.diff
index 596b4ac9b1e5b..26de859576896 100644
--- a/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.32bit.panic-unwind.diff
+++ b/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.32bit.panic-unwind.diff
@@ -32,7 +32,7 @@
           _14 = const main::promoted[0];
           _4 = copy _14;
           _3 = copy _4;
-          _2 = move _3 as &[u32] (PointerCoercion(Unsize));
+          _2 = move _3 as &[u32] (PointerCoercion(Unsize, AsCast));
           StorageDead(_3);
           StorageLive(_6);
           _6 = const 1_usize;
diff --git a/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.64bit.panic-abort.diff b/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.64bit.panic-abort.diff
index 40632db667a8d..e71992316dcf4 100644
--- a/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.64bit.panic-abort.diff
+++ b/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.64bit.panic-abort.diff
@@ -32,7 +32,7 @@
           _14 = const main::promoted[0];
           _4 = copy _14;
           _3 = copy _4;
-          _2 = move _3 as &[u32] (PointerCoercion(Unsize));
+          _2 = move _3 as &[u32] (PointerCoercion(Unsize, AsCast));
           StorageDead(_3);
           StorageLive(_6);
           _6 = const 1_usize;
diff --git a/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.64bit.panic-unwind.diff b/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.64bit.panic-unwind.diff
index 596b4ac9b1e5b..26de859576896 100644
--- a/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.64bit.panic-unwind.diff
+++ b/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.64bit.panic-unwind.diff
@@ -32,7 +32,7 @@
           _14 = const main::promoted[0];
           _4 = copy _14;
           _3 = copy _4;
-          _2 = move _3 as &[u32] (PointerCoercion(Unsize));
+          _2 = move _3 as &[u32] (PointerCoercion(Unsize, AsCast));
           StorageDead(_3);
           StorageLive(_6);
           _6 = const 1_usize;
diff --git a/tests/mir-opt/gvn.array_len.GVN.panic-abort.diff b/tests/mir-opt/gvn.array_len.GVN.panic-abort.diff
index 90654e0566284..0d0477fe7729f 100644
--- a/tests/mir-opt/gvn.array_len.GVN.panic-abort.diff
+++ b/tests/mir-opt/gvn.array_len.GVN.panic-abort.diff
@@ -16,7 +16,7 @@
 +         nop;
           StorageLive(_3);
           _3 = &(*_1);
-          _2 = move _3 as &[i32] (PointerCoercion(Unsize));
+          _2 = move _3 as &[i32] (PointerCoercion(Unsize, Implicit));
           StorageDead(_3);
           StorageLive(_4);
           _4 = &raw const (*_2);
diff --git a/tests/mir-opt/gvn.array_len.GVN.panic-unwind.diff b/tests/mir-opt/gvn.array_len.GVN.panic-unwind.diff
index 90654e0566284..0d0477fe7729f 100644
--- a/tests/mir-opt/gvn.array_len.GVN.panic-unwind.diff
+++ b/tests/mir-opt/gvn.array_len.GVN.panic-unwind.diff
@@ -16,7 +16,7 @@
 +         nop;
           StorageLive(_3);
           _3 = &(*_1);
-          _2 = move _3 as &[i32] (PointerCoercion(Unsize));
+          _2 = move _3 as &[i32] (PointerCoercion(Unsize, Implicit));
           StorageDead(_3);
           StorageLive(_4);
           _4 = &raw const (*_2);
diff --git a/tests/mir-opt/gvn.fn_pointers.GVN.panic-abort.diff b/tests/mir-opt/gvn.fn_pointers.GVN.panic-abort.diff
index 292b812b50c85..130b011630cc2 100644
--- a/tests/mir-opt/gvn.fn_pointers.GVN.panic-abort.diff
+++ b/tests/mir-opt/gvn.fn_pointers.GVN.panic-abort.diff
@@ -37,7 +37,7 @@
       bb0: {
 -         StorageLive(_1);
 +         nop;
-          _1 = identity::<u8> as fn(u8) -> u8 (PointerCoercion(ReifyFnPointer));
+          _1 = identity::<u8> as fn(u8) -> u8 (PointerCoercion(ReifyFnPointer, AsCast));
           StorageLive(_2);
           StorageLive(_3);
           _3 = copy _1;
@@ -50,7 +50,7 @@
           StorageDead(_2);
 -         StorageLive(_4);
 +         nop;
-          _4 = identity::<u8> as fn(u8) -> u8 (PointerCoercion(ReifyFnPointer));
+          _4 = identity::<u8> as fn(u8) -> u8 (PointerCoercion(ReifyFnPointer, AsCast));
           StorageLive(_5);
           StorageLive(_6);
           _6 = copy _4;
@@ -69,9 +69,9 @@
 +         nop;
           StorageLive(_9);
 -         _9 = copy _7;
--         _8 = move _9 as fn() (PointerCoercion(ClosureFnPointer(Safe)));
+-         _8 = move _9 as fn() (PointerCoercion(ClosureFnPointer(Safe), AsCast));
 +         _9 = const ZeroSized: {closure@$DIR/gvn.rs:614:19: 614:21};
-+         _8 = const ZeroSized: {closure@$DIR/gvn.rs:614:19: 614:21} as fn() (PointerCoercion(ClosureFnPointer(Safe)));
++         _8 = const ZeroSized: {closure@$DIR/gvn.rs:614:19: 614:21} as fn() (PointerCoercion(ClosureFnPointer(Safe), AsCast));
           StorageDead(_9);
           StorageLive(_10);
           StorageLive(_11);
@@ -87,9 +87,9 @@
 +         nop;
           StorageLive(_13);
 -         _13 = copy _7;
--         _12 = move _13 as fn() (PointerCoercion(ClosureFnPointer(Safe)));
+-         _12 = move _13 as fn() (PointerCoercion(ClosureFnPointer(Safe), AsCast));
 +         _13 = const ZeroSized: {closure@$DIR/gvn.rs:614:19: 614:21};
-+         _12 = const ZeroSized: {closure@$DIR/gvn.rs:614:19: 614:21} as fn() (PointerCoercion(ClosureFnPointer(Safe)));
++         _12 = const ZeroSized: {closure@$DIR/gvn.rs:614:19: 614:21} as fn() (PointerCoercion(ClosureFnPointer(Safe), AsCast));
           StorageDead(_13);
           StorageLive(_14);
           StorageLive(_15);
diff --git a/tests/mir-opt/gvn.fn_pointers.GVN.panic-unwind.diff b/tests/mir-opt/gvn.fn_pointers.GVN.panic-unwind.diff
index a60d986132e56..372a08d547306 100644
--- a/tests/mir-opt/gvn.fn_pointers.GVN.panic-unwind.diff
+++ b/tests/mir-opt/gvn.fn_pointers.GVN.panic-unwind.diff
@@ -37,7 +37,7 @@
       bb0: {
 -         StorageLive(_1);
 +         nop;
-          _1 = identity::<u8> as fn(u8) -> u8 (PointerCoercion(ReifyFnPointer));
+          _1 = identity::<u8> as fn(u8) -> u8 (PointerCoercion(ReifyFnPointer, AsCast));
           StorageLive(_2);
           StorageLive(_3);
           _3 = copy _1;
@@ -50,7 +50,7 @@
           StorageDead(_2);
 -         StorageLive(_4);
 +         nop;
-          _4 = identity::<u8> as fn(u8) -> u8 (PointerCoercion(ReifyFnPointer));
+          _4 = identity::<u8> as fn(u8) -> u8 (PointerCoercion(ReifyFnPointer, AsCast));
           StorageLive(_5);
           StorageLive(_6);
           _6 = copy _4;
@@ -69,9 +69,9 @@
 +         nop;
           StorageLive(_9);
 -         _9 = copy _7;
--         _8 = move _9 as fn() (PointerCoercion(ClosureFnPointer(Safe)));
+-         _8 = move _9 as fn() (PointerCoercion(ClosureFnPointer(Safe), AsCast));
 +         _9 = const ZeroSized: {closure@$DIR/gvn.rs:614:19: 614:21};
-+         _8 = const ZeroSized: {closure@$DIR/gvn.rs:614:19: 614:21} as fn() (PointerCoercion(ClosureFnPointer(Safe)));
++         _8 = const ZeroSized: {closure@$DIR/gvn.rs:614:19: 614:21} as fn() (PointerCoercion(ClosureFnPointer(Safe), AsCast));
           StorageDead(_9);
           StorageLive(_10);
           StorageLive(_11);
@@ -87,9 +87,9 @@
 +         nop;
           StorageLive(_13);
 -         _13 = copy _7;
--         _12 = move _13 as fn() (PointerCoercion(ClosureFnPointer(Safe)));
+-         _12 = move _13 as fn() (PointerCoercion(ClosureFnPointer(Safe), AsCast));
 +         _13 = const ZeroSized: {closure@$DIR/gvn.rs:614:19: 614:21};
-+         _12 = const ZeroSized: {closure@$DIR/gvn.rs:614:19: 614:21} as fn() (PointerCoercion(ClosureFnPointer(Safe)));
++         _12 = const ZeroSized: {closure@$DIR/gvn.rs:614:19: 614:21} as fn() (PointerCoercion(ClosureFnPointer(Safe), AsCast));
           StorageDead(_13);
           StorageLive(_14);
           StorageLive(_15);
diff --git a/tests/mir-opt/gvn.wide_ptr_provenance.GVN.panic-abort.diff b/tests/mir-opt/gvn.wide_ptr_provenance.GVN.panic-abort.diff
index c58362e391c43..43cd8ba7809a2 100644
--- a/tests/mir-opt/gvn.wide_ptr_provenance.GVN.panic-abort.diff
+++ b/tests/mir-opt/gvn.wide_ptr_provenance.GVN.panic-abort.diff
@@ -64,10 +64,10 @@
           _44 = const wide_ptr_provenance::promoted[1];
           _5 = &(*_44);
           _4 = &(*_5);
-          _3 = move _4 as &dyn std::marker::Send (PointerCoercion(Unsize));
+          _3 = move _4 as &dyn std::marker::Send (PointerCoercion(Unsize, AsCast));
           StorageDead(_4);
           _2 = &raw const (*_3);
--         _1 = move _2 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _1 = move _2 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 -         StorageDead(_2);
 +         _1 = copy _2;
 +         nop;
@@ -82,10 +82,10 @@
           _43 = const wide_ptr_provenance::promoted[0];
           _11 = &(*_43);
           _10 = &(*_11);
-          _9 = move _10 as &dyn std::marker::Send (PointerCoercion(Unsize));
+          _9 = move _10 as &dyn std::marker::Send (PointerCoercion(Unsize, AsCast));
           StorageDead(_10);
           _8 = &raw const (*_9);
--         _7 = move _8 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _7 = move _8 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 -         StorageDead(_8);
 +         _7 = copy _8;
 +         nop;
@@ -99,7 +99,7 @@
           StorageLive(_16);
           StorageLive(_17);
 -         _17 = copy _7;
--         _16 = move _17 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _16 = move _17 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _17 = copy _8;
 +         _16 = copy _8;
           StorageDead(_17);
@@ -121,7 +121,7 @@
           StorageLive(_21);
           StorageLive(_22);
 -         _22 = copy _7;
--         _21 = move _22 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _21 = move _22 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _22 = copy _8;
 +         _21 = copy _8;
           StorageDead(_22);
@@ -143,7 +143,7 @@
           StorageLive(_26);
           StorageLive(_27);
 -         _27 = copy _7;
--         _26 = move _27 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _26 = move _27 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _27 = copy _8;
 +         _26 = copy _8;
           StorageDead(_27);
@@ -165,7 +165,7 @@
           StorageLive(_31);
           StorageLive(_32);
 -         _32 = copy _7;
--         _31 = move _32 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _31 = move _32 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _32 = copy _8;
 +         _31 = copy _8;
           StorageDead(_32);
@@ -187,7 +187,7 @@
           StorageLive(_36);
           StorageLive(_37);
 -         _37 = copy _7;
--         _36 = move _37 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _36 = move _37 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _37 = copy _8;
 +         _36 = copy _8;
           StorageDead(_37);
@@ -209,7 +209,7 @@
           StorageLive(_41);
           StorageLive(_42);
 -         _42 = copy _7;
--         _41 = move _42 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _41 = move _42 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _42 = copy _8;
 +         _41 = copy _8;
           StorageDead(_42);
diff --git a/tests/mir-opt/gvn.wide_ptr_provenance.GVN.panic-unwind.diff b/tests/mir-opt/gvn.wide_ptr_provenance.GVN.panic-unwind.diff
index b29ee862c81a3..49cca20153bd4 100644
--- a/tests/mir-opt/gvn.wide_ptr_provenance.GVN.panic-unwind.diff
+++ b/tests/mir-opt/gvn.wide_ptr_provenance.GVN.panic-unwind.diff
@@ -64,10 +64,10 @@
           _44 = const wide_ptr_provenance::promoted[1];
           _5 = &(*_44);
           _4 = &(*_5);
-          _3 = move _4 as &dyn std::marker::Send (PointerCoercion(Unsize));
+          _3 = move _4 as &dyn std::marker::Send (PointerCoercion(Unsize, AsCast));
           StorageDead(_4);
           _2 = &raw const (*_3);
--         _1 = move _2 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _1 = move _2 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 -         StorageDead(_2);
 +         _1 = copy _2;
 +         nop;
@@ -82,10 +82,10 @@
           _43 = const wide_ptr_provenance::promoted[0];
           _11 = &(*_43);
           _10 = &(*_11);
-          _9 = move _10 as &dyn std::marker::Send (PointerCoercion(Unsize));
+          _9 = move _10 as &dyn std::marker::Send (PointerCoercion(Unsize, AsCast));
           StorageDead(_10);
           _8 = &raw const (*_9);
--         _7 = move _8 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _7 = move _8 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 -         StorageDead(_8);
 +         _7 = copy _8;
 +         nop;
@@ -99,7 +99,7 @@
           StorageLive(_16);
           StorageLive(_17);
 -         _17 = copy _7;
--         _16 = move _17 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _16 = move _17 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _17 = copy _8;
 +         _16 = copy _8;
           StorageDead(_17);
@@ -121,7 +121,7 @@
           StorageLive(_21);
           StorageLive(_22);
 -         _22 = copy _7;
--         _21 = move _22 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _21 = move _22 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _22 = copy _8;
 +         _21 = copy _8;
           StorageDead(_22);
@@ -143,7 +143,7 @@
           StorageLive(_26);
           StorageLive(_27);
 -         _27 = copy _7;
--         _26 = move _27 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _26 = move _27 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _27 = copy _8;
 +         _26 = copy _8;
           StorageDead(_27);
@@ -165,7 +165,7 @@
           StorageLive(_31);
           StorageLive(_32);
 -         _32 = copy _7;
--         _31 = move _32 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _31 = move _32 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _32 = copy _8;
 +         _31 = copy _8;
           StorageDead(_32);
@@ -187,7 +187,7 @@
           StorageLive(_36);
           StorageLive(_37);
 -         _37 = copy _7;
--         _36 = move _37 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _36 = move _37 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _37 = copy _8;
 +         _36 = copy _8;
           StorageDead(_37);
@@ -209,7 +209,7 @@
           StorageLive(_41);
           StorageLive(_42);
 -         _42 = copy _7;
--         _41 = move _42 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _41 = move _42 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _42 = copy _8;
 +         _41 = copy _8;
           StorageDead(_42);
diff --git a/tests/mir-opt/gvn.wide_ptr_same_provenance.GVN.panic-abort.diff b/tests/mir-opt/gvn.wide_ptr_same_provenance.GVN.panic-abort.diff
index f4c38b7ab071e..6b6152c1117e3 100644
--- a/tests/mir-opt/gvn.wide_ptr_same_provenance.GVN.panic-abort.diff
+++ b/tests/mir-opt/gvn.wide_ptr_same_provenance.GVN.panic-abort.diff
@@ -86,10 +86,10 @@
 -         _7 = &(*_1)[_8];
 +         _7 = &(*_1)[0 of 1];
           _6 = &(*_7);
-          _5 = move _6 as &dyn std::marker::Send (PointerCoercion(Unsize));
+          _5 = move _6 as &dyn std::marker::Send (PointerCoercion(Unsize, AsCast));
           StorageDead(_6);
           _4 = &raw const (*_5);
--         _3 = move _4 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _3 = move _4 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 -         StorageDead(_4);
 +         _3 = copy _4;
 +         nop;
@@ -115,10 +115,10 @@
 -         _15 = &(*_1)[_16];
 +         _15 = &(*_1)[1 of 2];
           _14 = &(*_15);
-          _13 = move _14 as &dyn std::marker::Send (PointerCoercion(Unsize));
+          _13 = move _14 as &dyn std::marker::Send (PointerCoercion(Unsize, AsCast));
           StorageDead(_14);
           _12 = &raw const (*_13);
--         _11 = move _12 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _11 = move _12 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 -         StorageDead(_12);
 +         _11 = copy _12;
 +         nop;
@@ -132,7 +132,7 @@
           StorageLive(_22);
           StorageLive(_23);
 -         _23 = copy _11;
--         _22 = move _23 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _22 = move _23 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _23 = copy _12;
 +         _22 = copy _12;
           StorageDead(_23);
@@ -154,7 +154,7 @@
           StorageLive(_27);
           StorageLive(_28);
 -         _28 = copy _11;
--         _27 = move _28 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _27 = move _28 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _28 = copy _12;
 +         _27 = copy _12;
           StorageDead(_28);
@@ -176,7 +176,7 @@
           StorageLive(_32);
           StorageLive(_33);
 -         _33 = copy _11;
--         _32 = move _33 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _32 = move _33 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _33 = copy _12;
 +         _32 = copy _12;
           StorageDead(_33);
@@ -198,7 +198,7 @@
           StorageLive(_37);
           StorageLive(_38);
 -         _38 = copy _11;
--         _37 = move _38 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _37 = move _38 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _38 = copy _12;
 +         _37 = copy _12;
           StorageDead(_38);
@@ -220,7 +220,7 @@
           StorageLive(_42);
           StorageLive(_43);
 -         _43 = copy _11;
--         _42 = move _43 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _42 = move _43 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _43 = copy _12;
 +         _42 = copy _12;
           StorageDead(_43);
@@ -242,7 +242,7 @@
           StorageLive(_47);
           StorageLive(_48);
 -         _48 = copy _11;
--         _47 = move _48 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _47 = move _48 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _48 = copy _12;
 +         _47 = copy _12;
           StorageDead(_48);
diff --git a/tests/mir-opt/gvn.wide_ptr_same_provenance.GVN.panic-unwind.diff b/tests/mir-opt/gvn.wide_ptr_same_provenance.GVN.panic-unwind.diff
index 03f2d129a9b6f..093c1ec6ce379 100644
--- a/tests/mir-opt/gvn.wide_ptr_same_provenance.GVN.panic-unwind.diff
+++ b/tests/mir-opt/gvn.wide_ptr_same_provenance.GVN.panic-unwind.diff
@@ -86,10 +86,10 @@
 -         _7 = &(*_1)[_8];
 +         _7 = &(*_1)[0 of 1];
           _6 = &(*_7);
-          _5 = move _6 as &dyn std::marker::Send (PointerCoercion(Unsize));
+          _5 = move _6 as &dyn std::marker::Send (PointerCoercion(Unsize, AsCast));
           StorageDead(_6);
           _4 = &raw const (*_5);
--         _3 = move _4 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _3 = move _4 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 -         StorageDead(_4);
 +         _3 = copy _4;
 +         nop;
@@ -115,10 +115,10 @@
 -         _15 = &(*_1)[_16];
 +         _15 = &(*_1)[1 of 2];
           _14 = &(*_15);
-          _13 = move _14 as &dyn std::marker::Send (PointerCoercion(Unsize));
+          _13 = move _14 as &dyn std::marker::Send (PointerCoercion(Unsize, AsCast));
           StorageDead(_14);
           _12 = &raw const (*_13);
--         _11 = move _12 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _11 = move _12 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 -         StorageDead(_12);
 +         _11 = copy _12;
 +         nop;
@@ -132,7 +132,7 @@
           StorageLive(_22);
           StorageLive(_23);
 -         _23 = copy _11;
--         _22 = move _23 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _22 = move _23 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _23 = copy _12;
 +         _22 = copy _12;
           StorageDead(_23);
@@ -154,7 +154,7 @@
           StorageLive(_27);
           StorageLive(_28);
 -         _28 = copy _11;
--         _27 = move _28 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _27 = move _28 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _28 = copy _12;
 +         _27 = copy _12;
           StorageDead(_28);
@@ -176,7 +176,7 @@
           StorageLive(_32);
           StorageLive(_33);
 -         _33 = copy _11;
--         _32 = move _33 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _32 = move _33 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _33 = copy _12;
 +         _32 = copy _12;
           StorageDead(_33);
@@ -198,7 +198,7 @@
           StorageLive(_37);
           StorageLive(_38);
 -         _38 = copy _11;
--         _37 = move _38 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _37 = move _38 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _38 = copy _12;
 +         _37 = copy _12;
           StorageDead(_38);
@@ -220,7 +220,7 @@
           StorageLive(_42);
           StorageLive(_43);
 -         _43 = copy _11;
--         _42 = move _43 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _42 = move _43 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _43 = copy _12;
 +         _42 = copy _12;
           StorageDead(_43);
@@ -242,7 +242,7 @@
           StorageLive(_47);
           StorageLive(_48);
 -         _48 = copy _11;
--         _47 = move _48 as *const dyn std::marker::Send (PointerCoercion(Unsize));
+-         _47 = move _48 as *const dyn std::marker::Send (PointerCoercion(Unsize, Implicit));
 +         _48 = copy _12;
 +         _47 = copy _12;
           StorageDead(_48);
diff --git a/tests/mir-opt/inline/dyn_trait.get_query.Inline.panic-abort.diff b/tests/mir-opt/inline/dyn_trait.get_query.Inline.panic-abort.diff
index 2d64d49ce5c13..df79001ce75b6 100644
--- a/tests/mir-opt/inline/dyn_trait.get_query.Inline.panic-abort.diff
+++ b/tests/mir-opt/inline/dyn_trait.get_query.Inline.panic-abort.diff
@@ -31,7 +31,7 @@
           _4 = copy _2;
 -         _0 = try_execute_query::<<Q as Query>::C>(move _4) -> [return: bb2, unwind unreachable];
 +         StorageLive(_5);
-+         _5 = copy _4 as &dyn Cache<V = <Q as Query>::V> (PointerCoercion(Unsize));
++         _5 = copy _4 as &dyn Cache<V = <Q as Query>::V> (PointerCoercion(Unsize, Implicit));
 +         _0 = <dyn Cache<V = <Q as Query>::V> as Cache>::store_nocache(move _5) -> [return: bb2, unwind unreachable];
       }
   
diff --git a/tests/mir-opt/inline/dyn_trait.get_query.Inline.panic-unwind.diff b/tests/mir-opt/inline/dyn_trait.get_query.Inline.panic-unwind.diff
index c5e9654e19cfd..014f950940c5f 100644
--- a/tests/mir-opt/inline/dyn_trait.get_query.Inline.panic-unwind.diff
+++ b/tests/mir-opt/inline/dyn_trait.get_query.Inline.panic-unwind.diff
@@ -31,7 +31,7 @@
           _4 = copy _2;
 -         _0 = try_execute_query::<<Q as Query>::C>(move _4) -> [return: bb2, unwind continue];
 +         StorageLive(_5);
-+         _5 = copy _4 as &dyn Cache<V = <Q as Query>::V> (PointerCoercion(Unsize));
++         _5 = copy _4 as &dyn Cache<V = <Q as Query>::V> (PointerCoercion(Unsize, Implicit));
 +         _0 = <dyn Cache<V = <Q as Query>::V> as Cache>::store_nocache(move _5) -> [return: bb2, unwind continue];
       }
   
diff --git a/tests/mir-opt/inline/dyn_trait.try_execute_query.Inline.panic-abort.diff b/tests/mir-opt/inline/dyn_trait.try_execute_query.Inline.panic-abort.diff
index f02ca6233173f..64d12461e8de1 100644
--- a/tests/mir-opt/inline/dyn_trait.try_execute_query.Inline.panic-abort.diff
+++ b/tests/mir-opt/inline/dyn_trait.try_execute_query.Inline.panic-abort.diff
@@ -14,7 +14,7 @@
           StorageLive(_2);
           StorageLive(_3);
           _3 = copy _1;
-          _2 = move _3 as &dyn Cache<V = <C as Cache>::V> (PointerCoercion(Unsize));
+          _2 = move _3 as &dyn Cache<V = <C as Cache>::V> (PointerCoercion(Unsize, Implicit));
           StorageDead(_3);
 -         _0 = mk_cycle::<<C as Cache>::V>(move _2) -> [return: bb1, unwind unreachable];
 +         _0 = <dyn Cache<V = <C as Cache>::V> as Cache>::store_nocache(move _2) -> [return: bb1, unwind unreachable];
diff --git a/tests/mir-opt/inline/dyn_trait.try_execute_query.Inline.panic-unwind.diff b/tests/mir-opt/inline/dyn_trait.try_execute_query.Inline.panic-unwind.diff
index 31080dff4ded7..21791cb0d2a59 100644
--- a/tests/mir-opt/inline/dyn_trait.try_execute_query.Inline.panic-unwind.diff
+++ b/tests/mir-opt/inline/dyn_trait.try_execute_query.Inline.panic-unwind.diff
@@ -14,7 +14,7 @@
           StorageLive(_2);
           StorageLive(_3);
           _3 = copy _1;
-          _2 = move _3 as &dyn Cache<V = <C as Cache>::V> (PointerCoercion(Unsize));
+          _2 = move _3 as &dyn Cache<V = <C as Cache>::V> (PointerCoercion(Unsize, Implicit));
           StorageDead(_3);
 -         _0 = mk_cycle::<<C as Cache>::V>(move _2) -> [return: bb1, unwind continue];
 +         _0 = <dyn Cache<V = <C as Cache>::V> as Cache>::store_nocache(move _2) -> [return: bb1, unwind continue];
diff --git a/tests/mir-opt/issue_76432.test.SimplifyComparisonIntegral.panic-abort.diff b/tests/mir-opt/issue_76432.test.SimplifyComparisonIntegral.panic-abort.diff
index f03691ad67316..c02bab3524bca 100644
--- a/tests/mir-opt/issue_76432.test.SimplifyComparisonIntegral.panic-abort.diff
+++ b/tests/mir-opt/issue_76432.test.SimplifyComparisonIntegral.panic-abort.diff
@@ -26,7 +26,7 @@
           StorageLive(_4);
           _4 = [copy _1, copy _1, copy _1];
           _3 = &_4;
-          _2 = copy _3 as &[T] (PointerCoercion(Unsize));
+          _2 = copy _3 as &[T] (PointerCoercion(Unsize, Implicit));
           nop;
           nop;
           goto -> bb2;
diff --git a/tests/mir-opt/issue_76432.test.SimplifyComparisonIntegral.panic-unwind.diff b/tests/mir-opt/issue_76432.test.SimplifyComparisonIntegral.panic-unwind.diff
index 633e5c740a1a8..49be042588cb3 100644
--- a/tests/mir-opt/issue_76432.test.SimplifyComparisonIntegral.panic-unwind.diff
+++ b/tests/mir-opt/issue_76432.test.SimplifyComparisonIntegral.panic-unwind.diff
@@ -26,7 +26,7 @@
           StorageLive(_4);
           _4 = [copy _1, copy _1, copy _1];
           _3 = &_4;
-          _2 = copy _3 as &[T] (PointerCoercion(Unsize));
+          _2 = copy _3 as &[T] (PointerCoercion(Unsize, Implicit));
           nop;
           nop;
           goto -> bb2;
diff --git a/tests/mir-opt/lower_array_len.array_bound.GVN.panic-abort.diff b/tests/mir-opt/lower_array_len.array_bound.GVN.panic-abort.diff
index 8223cbbb41216..f052c8f63dcaa 100644
--- a/tests/mir-opt/lower_array_len.array_bound.GVN.panic-abort.diff
+++ b/tests/mir-opt/lower_array_len.array_bound.GVN.panic-abort.diff
@@ -24,7 +24,7 @@
           StorageLive(_6);
           StorageLive(_7);
           _7 = &(*_2);
-          _6 = move _7 as &[u8] (PointerCoercion(Unsize));
+          _6 = move _7 as &[u8] (PointerCoercion(Unsize, Implicit));
           StorageDead(_7);
 -         _5 = PtrMetadata(move _6);
 +         _5 = const N;
diff --git a/tests/mir-opt/lower_array_len.array_bound.GVN.panic-unwind.diff b/tests/mir-opt/lower_array_len.array_bound.GVN.panic-unwind.diff
index d8f33accbc005..3299e3004317d 100644
--- a/tests/mir-opt/lower_array_len.array_bound.GVN.panic-unwind.diff
+++ b/tests/mir-opt/lower_array_len.array_bound.GVN.panic-unwind.diff
@@ -24,7 +24,7 @@
           StorageLive(_6);
           StorageLive(_7);
           _7 = &(*_2);
-          _6 = move _7 as &[u8] (PointerCoercion(Unsize));
+          _6 = move _7 as &[u8] (PointerCoercion(Unsize, Implicit));
           StorageDead(_7);
 -         _5 = PtrMetadata(move _6);
 +         _5 = const N;
diff --git a/tests/mir-opt/lower_array_len.array_bound_mut.GVN.panic-abort.diff b/tests/mir-opt/lower_array_len.array_bound_mut.GVN.panic-abort.diff
index 1cb9963c00e94..329eb80b3c4f5 100644
--- a/tests/mir-opt/lower_array_len.array_bound_mut.GVN.panic-abort.diff
+++ b/tests/mir-opt/lower_array_len.array_bound_mut.GVN.panic-abort.diff
@@ -27,7 +27,7 @@
           StorageLive(_6);
           StorageLive(_7);
           _7 = &(*_2);
-          _6 = move _7 as &[u8] (PointerCoercion(Unsize));
+          _6 = move _7 as &[u8] (PointerCoercion(Unsize, Implicit));
           StorageDead(_7);
 -         _5 = PtrMetadata(move _6);
 +         _5 = const N;
diff --git a/tests/mir-opt/lower_array_len.array_bound_mut.GVN.panic-unwind.diff b/tests/mir-opt/lower_array_len.array_bound_mut.GVN.panic-unwind.diff
index fa4e11ed20192..ab007e133ecc1 100644
--- a/tests/mir-opt/lower_array_len.array_bound_mut.GVN.panic-unwind.diff
+++ b/tests/mir-opt/lower_array_len.array_bound_mut.GVN.panic-unwind.diff
@@ -27,7 +27,7 @@
           StorageLive(_6);
           StorageLive(_7);
           _7 = &(*_2);
-          _6 = move _7 as &[u8] (PointerCoercion(Unsize));
+          _6 = move _7 as &[u8] (PointerCoercion(Unsize, Implicit));
           StorageDead(_7);
 -         _5 = PtrMetadata(move _6);
 +         _5 = const N;
diff --git a/tests/mir-opt/lower_array_len.array_len.GVN.panic-abort.diff b/tests/mir-opt/lower_array_len.array_len.GVN.panic-abort.diff
index 9c1b9a708c59a..369bd2f473297 100644
--- a/tests/mir-opt/lower_array_len.array_len.GVN.panic-abort.diff
+++ b/tests/mir-opt/lower_array_len.array_len.GVN.panic-abort.diff
@@ -11,7 +11,7 @@
           StorageLive(_2);
           StorageLive(_3);
           _3 = &(*_1);
-          _2 = move _3 as &[u8] (PointerCoercion(Unsize));
+          _2 = move _3 as &[u8] (PointerCoercion(Unsize, Implicit));
           StorageDead(_3);
 -         _0 = PtrMetadata(move _2);
 +         _0 = const N;
diff --git a/tests/mir-opt/lower_array_len.array_len.GVN.panic-unwind.diff b/tests/mir-opt/lower_array_len.array_len.GVN.panic-unwind.diff
index 9c1b9a708c59a..369bd2f473297 100644
--- a/tests/mir-opt/lower_array_len.array_len.GVN.panic-unwind.diff
+++ b/tests/mir-opt/lower_array_len.array_len.GVN.panic-unwind.diff
@@ -11,7 +11,7 @@
           StorageLive(_2);
           StorageLive(_3);
           _3 = &(*_1);
-          _2 = move _3 as &[u8] (PointerCoercion(Unsize));
+          _2 = move _3 as &[u8] (PointerCoercion(Unsize, Implicit));
           StorageDead(_3);
 -         _0 = PtrMetadata(move _2);
 +         _0 = const N;
diff --git a/tests/mir-opt/lower_array_len.array_len_by_value.GVN.panic-abort.diff b/tests/mir-opt/lower_array_len.array_len_by_value.GVN.panic-abort.diff
index 97fa503ac2e46..d9c289bf58aee 100644
--- a/tests/mir-opt/lower_array_len.array_len_by_value.GVN.panic-abort.diff
+++ b/tests/mir-opt/lower_array_len.array_len_by_value.GVN.panic-abort.diff
@@ -11,7 +11,7 @@
           StorageLive(_2);
           StorageLive(_3);
           _3 = &_1;
-          _2 = move _3 as &[u8] (PointerCoercion(Unsize));
+          _2 = move _3 as &[u8] (PointerCoercion(Unsize, Implicit));
           StorageDead(_3);
 -         _0 = PtrMetadata(move _2);
 +         _0 = const N;
diff --git a/tests/mir-opt/lower_array_len.array_len_by_value.GVN.panic-unwind.diff b/tests/mir-opt/lower_array_len.array_len_by_value.GVN.panic-unwind.diff
index 97fa503ac2e46..d9c289bf58aee 100644
--- a/tests/mir-opt/lower_array_len.array_len_by_value.GVN.panic-unwind.diff
+++ b/tests/mir-opt/lower_array_len.array_len_by_value.GVN.panic-unwind.diff
@@ -11,7 +11,7 @@
           StorageLive(_2);
           StorageLive(_3);
           _3 = &_1;
-          _2 = move _3 as &[u8] (PointerCoercion(Unsize));
+          _2 = move _3 as &[u8] (PointerCoercion(Unsize, Implicit));
           StorageDead(_3);
 -         _0 = PtrMetadata(move _2);
 +         _0 = const N;
diff --git a/tests/mir-opt/lower_array_len.array_len_raw.GVN.panic-abort.diff b/tests/mir-opt/lower_array_len.array_len_raw.GVN.panic-abort.diff
index b5e8b66813ae3..180a7db029794 100644
--- a/tests/mir-opt/lower_array_len.array_len_raw.GVN.panic-abort.diff
+++ b/tests/mir-opt/lower_array_len.array_len_raw.GVN.panic-abort.diff
@@ -24,7 +24,7 @@
           StorageLive(_4);
           _4 = &_1;
           _3 = &(*_4);
-          _2 = move _3 as &[u8] (PointerCoercion(Unsize));
+          _2 = move _3 as &[u8] (PointerCoercion(Unsize, Implicit));
           StorageDead(_3);
           StorageDead(_4);
           StorageLive(_5);
diff --git a/tests/mir-opt/lower_array_len.array_len_raw.GVN.panic-unwind.diff b/tests/mir-opt/lower_array_len.array_len_raw.GVN.panic-unwind.diff
index b5e8b66813ae3..180a7db029794 100644
--- a/tests/mir-opt/lower_array_len.array_len_raw.GVN.panic-unwind.diff
+++ b/tests/mir-opt/lower_array_len.array_len_raw.GVN.panic-unwind.diff
@@ -24,7 +24,7 @@
           StorageLive(_4);
           _4 = &_1;
           _3 = &(*_4);
-          _2 = move _3 as &[u8] (PointerCoercion(Unsize));
+          _2 = move _3 as &[u8] (PointerCoercion(Unsize, Implicit));
           StorageDead(_3);
           StorageDead(_4);
           StorageLive(_5);
diff --git a/tests/mir-opt/lower_array_len.array_len_reborrow.GVN.panic-abort.diff b/tests/mir-opt/lower_array_len.array_len_reborrow.GVN.panic-abort.diff
index 0299c6acd804a..49964f8b49e26 100644
--- a/tests/mir-opt/lower_array_len.array_len_reborrow.GVN.panic-abort.diff
+++ b/tests/mir-opt/lower_array_len.array_len_reborrow.GVN.panic-abort.diff
@@ -23,7 +23,7 @@
           StorageLive(_4);
           _4 = &mut _1;
           _3 = &mut (*_4);
-          _2 = move _3 as &mut [u8] (PointerCoercion(Unsize));
+          _2 = move _3 as &mut [u8] (PointerCoercion(Unsize, Implicit));
           StorageDead(_3);
           StorageDead(_4);
           StorageLive(_5);
diff --git a/tests/mir-opt/lower_array_len.array_len_reborrow.GVN.panic-unwind.diff b/tests/mir-opt/lower_array_len.array_len_reborrow.GVN.panic-unwind.diff
index 0299c6acd804a..49964f8b49e26 100644
--- a/tests/mir-opt/lower_array_len.array_len_reborrow.GVN.panic-unwind.diff
+++ b/tests/mir-opt/lower_array_len.array_len_reborrow.GVN.panic-unwind.diff
@@ -23,7 +23,7 @@
           StorageLive(_4);
           _4 = &mut _1;
           _3 = &mut (*_4);
-          _2 = move _3 as &mut [u8] (PointerCoercion(Unsize));
+          _2 = move _3 as &mut [u8] (PointerCoercion(Unsize, Implicit));
           StorageDead(_3);
           StorageDead(_4);
           StorageLive(_5);
diff --git a/tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.32bit.panic-abort.diff b/tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.32bit.panic-abort.diff
index 6cac8b109eea6..87fbcca917736 100644
--- a/tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.32bit.panic-abort.diff
+++ b/tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.32bit.panic-abort.diff
@@ -93,7 +93,7 @@
       bb5: {
           StorageLive(_15);
           _16 = &_13;
-          _15 = copy _16 as &dyn std::fmt::Debug (PointerCoercion(Unsize));
+          _15 = copy _16 as &dyn std::fmt::Debug (PointerCoercion(Unsize, Implicit));
           _14 = result::unwrap_failed(const "called `Result::unwrap()` on an `Err` value", move _15) -> unwind unreachable;
       }
   
diff --git a/tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.64bit.panic-abort.diff b/tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.64bit.panic-abort.diff
index 10fde25e3178b..13258c171605c 100644
--- a/tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.64bit.panic-abort.diff
+++ b/tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.64bit.panic-abort.diff
@@ -93,7 +93,7 @@
       bb5: {
           StorageLive(_15);
           _16 = &_13;
-          _15 = copy _16 as &dyn std::fmt::Debug (PointerCoercion(Unsize));
+          _15 = copy _16 as &dyn std::fmt::Debug (PointerCoercion(Unsize, Implicit));
           _14 = result::unwrap_failed(const "called `Result::unwrap()` on an `Err` value", move _15) -> unwind unreachable;
       }
   
diff --git a/tests/mir-opt/retag.main.SimplifyCfg-pre-optimizations.after.panic-abort.mir b/tests/mir-opt/retag.main.SimplifyCfg-pre-optimizations.after.panic-abort.mir
index d0f454e456934..cca2b3ae188c3 100644
--- a/tests/mir-opt/retag.main.SimplifyCfg-pre-optimizations.after.panic-abort.mir
+++ b/tests/mir-opt/retag.main.SimplifyCfg-pre-optimizations.after.panic-abort.mir
@@ -105,7 +105,7 @@ fn main() -> () {
         StorageLive(_14);
         _14 = {closure@main::{closure#0}};
         Retag(_14);
-        _13 = move _14 as for<'a> fn(&'a i32) -> &'a i32 (PointerCoercion(ClosureFnPointer(Safe)));
+        _13 = move _14 as for<'a> fn(&'a i32) -> &'a i32 (PointerCoercion(ClosureFnPointer(Safe), Implicit));
         StorageDead(_14);
         StorageLive(_15);
         StorageLive(_16);
diff --git a/tests/mir-opt/retag.main.SimplifyCfg-pre-optimizations.after.panic-unwind.mir b/tests/mir-opt/retag.main.SimplifyCfg-pre-optimizations.after.panic-unwind.mir
index 685277d7a5328..bcd3a47ac04fb 100644
--- a/tests/mir-opt/retag.main.SimplifyCfg-pre-optimizations.after.panic-unwind.mir
+++ b/tests/mir-opt/retag.main.SimplifyCfg-pre-optimizations.after.panic-unwind.mir
@@ -105,7 +105,7 @@ fn main() -> () {
         StorageLive(_14);
         _14 = {closure@main::{closure#0}};
         Retag(_14);
-        _13 = move _14 as for<'a> fn(&'a i32) -> &'a i32 (PointerCoercion(ClosureFnPointer(Safe)));
+        _13 = move _14 as for<'a> fn(&'a i32) -> &'a i32 (PointerCoercion(ClosureFnPointer(Safe), Implicit));
         StorageDead(_14);
         StorageLive(_15);
         StorageLive(_16);
diff --git a/tests/mir-opt/simplify_locals.c.SimplifyLocals-before-const-prop.diff b/tests/mir-opt/simplify_locals.c.SimplifyLocals-before-const-prop.diff
index 7cc5e335cb00a..37a669d72b85e 100644
--- a/tests/mir-opt/simplify_locals.c.SimplifyLocals-before-const-prop.diff
+++ b/tests/mir-opt/simplify_locals.c.SimplifyLocals-before-const-prop.diff
@@ -21,7 +21,7 @@
 -         StorageLive(_4);
 -         _4 = &_1;
 -         _3 = &(*_4);
--         _2 = move _3 as &[u8] (PointerCoercion(Unsize));
+-         _2 = move _3 as &[u8] (PointerCoercion(Unsize, Implicit));
 -         StorageDead(_3);
 -         StorageDead(_4);
 -         StorageDead(_2);
diff --git a/tests/mir-opt/sroa/lifetimes.foo.ScalarReplacementOfAggregates.diff b/tests/mir-opt/sroa/lifetimes.foo.ScalarReplacementOfAggregates.diff
index 478dacc327668..a1df868cde051 100644
--- a/tests/mir-opt/sroa/lifetimes.foo.ScalarReplacementOfAggregates.diff
+++ b/tests/mir-opt/sroa/lifetimes.foo.ScalarReplacementOfAggregates.diff
@@ -61,7 +61,7 @@
       }
   
       bb1: {
-          _3 = move _4 as std::boxed::Box<dyn std::fmt::Display> (PointerCoercion(Unsize));
+          _3 = move _4 as std::boxed::Box<dyn std::fmt::Display> (PointerCoercion(Unsize, Implicit));
           StorageDead(_4);
           _2 = Result::<Box<dyn std::fmt::Display>, <T as Err>::Err>::Ok(move _3);
           StorageDead(_3);
diff --git a/tests/ui/lifetimes/issue-90600-expected-return-static-indirect.stderr b/tests/ui/lifetimes/issue-90600-expected-return-static-indirect.stderr
index 6bd6a0584c9f1..e4cd54ac33741 100644
--- a/tests/ui/lifetimes/issue-90600-expected-return-static-indirect.stderr
+++ b/tests/ui/lifetimes/issue-90600-expected-return-static-indirect.stderr
@@ -7,7 +7,7 @@ LL |     let refcell = RefCell::new(&mut foo);
    |                                ^^^^^^^^ borrowed value does not live long enough
 LL |
 LL |     let read = &refcell as &RefCell<dyn Read>;
-   |                -------- coercion requires that `foo` is borrowed for `'static`
+   |                ------------------------------ cast requires that `foo` is borrowed for `'static`
 ...
 LL | }
    |  - `foo` dropped here while still borrowed
@@ -19,7 +19,7 @@ LL | fn inner(mut foo: &[u8]) {
    |                   - let's call the lifetime of this reference `'1`
 ...
 LL |     let read = &refcell as &RefCell<dyn Read>;
-   |                ^^^^^^^^ coercion requires that `'1` must outlive `'static`
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cast requires that `'1` must outlive `'static`
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/regions/regions-close-object-into-object-4.stderr b/tests/ui/regions/regions-close-object-into-object-4.stderr
index b8b414b7e125e..f6a79be09477c 100644
--- a/tests/ui/regions/regions-close-object-into-object-4.stderr
+++ b/tests/ui/regions/regions-close-object-into-object-4.stderr
@@ -30,12 +30,11 @@ error[E0310]: the parameter type `U` may not live long enough
   --> $DIR/regions-close-object-into-object-4.rs:9:5
    |
 LL |     Box::new(B(&*v)) as Box<dyn X>
-   |     ^^^^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |     |
    |     the parameter type `U` must be valid for the static lifetime...
    |     ...so that the type `U` will meet its required lifetime bounds
    |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 help: consider adding an explicit lifetime bound
    |
 LL | fn i<'a, T, U: 'static>(v: Box<dyn A<U>+'a>) -> Box<dyn X + 'static> {
diff --git a/tests/ui/regions/regions-close-object-into-object-5.stderr b/tests/ui/regions/regions-close-object-into-object-5.stderr
index 4a2f4f847a308..881d9e03cdfab 100644
--- a/tests/ui/regions/regions-close-object-into-object-5.stderr
+++ b/tests/ui/regions/regions-close-object-into-object-5.stderr
@@ -30,12 +30,11 @@ error[E0310]: the parameter type `T` may not live long enough
   --> $DIR/regions-close-object-into-object-5.rs:17:5
    |
 LL |     Box::new(B(&*v)) as Box<dyn X>
-   |     ^^^^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |     |
    |     the parameter type `T` must be valid for the static lifetime...
    |     ...so that the type `T` will meet its required lifetime bounds
    |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 help: consider adding an explicit lifetime bound
    |
 LL | fn f<'a, T: 'static, U>(v: Box<A<T> + 'static>) -> Box<X + 'static> {
diff --git a/tests/ui/regions/regions-close-over-type-parameter-1.stderr b/tests/ui/regions/regions-close-over-type-parameter-1.stderr
index 1cd5b7f225079..7c8c5fe5cf68b 100644
--- a/tests/ui/regions/regions-close-over-type-parameter-1.stderr
+++ b/tests/ui/regions/regions-close-over-type-parameter-1.stderr
@@ -2,7 +2,7 @@ error[E0310]: the parameter type `A` may not live long enough
   --> $DIR/regions-close-over-type-parameter-1.rs:11:5
    |
 LL |     Box::new(v) as Box<dyn SomeTrait + 'static>
-   |     ^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |     |
    |     the parameter type `A` must be valid for the static lifetime...
    |     ...so that the type `A` will meet its required lifetime bounds
@@ -18,7 +18,7 @@ error[E0309]: the parameter type `A` may not live long enough
 LL | fn make_object3<'a, 'b, A: SomeTrait + 'a>(v: A) -> Box<dyn SomeTrait + 'b> {
    |                     -- the parameter type `A` must be valid for the lifetime `'b` as defined here...
 LL |     Box::new(v) as Box<dyn SomeTrait + 'b>
-   |     ^^^^^^^^^^^ ...so that the type `A` will meet its required lifetime bounds
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `A` will meet its required lifetime bounds
    |
 help: consider adding an explicit lifetime bound
    |
diff --git a/tests/ui/suggestions/lifetimes/suggest-using-tick-underscore-lifetime-in-return-trait-object.stderr b/tests/ui/suggestions/lifetimes/suggest-using-tick-underscore-lifetime-in-return-trait-object.stderr
index 050ef7da9b936..fa203150444c8 100644
--- a/tests/ui/suggestions/lifetimes/suggest-using-tick-underscore-lifetime-in-return-trait-object.stderr
+++ b/tests/ui/suggestions/lifetimes/suggest-using-tick-underscore-lifetime-in-return-trait-object.stderr
@@ -4,7 +4,7 @@ error: lifetime may not live long enough
 LL | fn foo<T: Any>(value: &T) -> Box<dyn Any> {
    |                       - let's call the lifetime of this reference `'1`
 LL |     Box::new(value) as Box<dyn Any>
-   |     ^^^^^^^^^^^^^^^ coercion requires that `'1` must outlive `'static`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cast requires that `'1` must outlive `'static`
    |
 help: to declare that the trait object captures data from argument `value`, you can add an explicit `'_` lifetime bound
    |

From 39f66baa68ed3ad0d60eb31020dd00ca2c05f811 Mon Sep 17 00:00:00 2001
From: Lukas Markeffsky <@>
Date: Wed, 11 Sep 2024 01:16:10 +0200
Subject: [PATCH 13/14] improve errors for invalid pointer casts

---
 compiler/rustc_hir_typeck/src/cast.rs         | 122 +++++++++++++-----
 tests/ui/cast/casts-differing-anon.stderr     |   2 +-
 .../cast/ptr-to-trait-obj-different-args.rs   |   8 +-
 .../ptr-to-trait-obj-different-args.stderr    |  41 ++----
 .../cast/ptr-to-trait-obj-wrap-upcast.stderr  |   2 +-
 tests/ui/mismatched_types/cast-rfc0401.stderr |   8 +-
 tests/ui/traits/upcast_soundness_bug.rs       |   2 +-
 tests/ui/traits/upcast_soundness_bug.stderr   |  10 +-
 8 files changed, 121 insertions(+), 74 deletions(-)

diff --git a/compiler/rustc_hir_typeck/src/cast.rs b/compiler/rustc_hir_typeck/src/cast.rs
index 9e20e1d9745a7..fcd2940b83ae3 100644
--- a/compiler/rustc_hir_typeck/src/cast.rs
+++ b/compiler/rustc_hir_typeck/src/cast.rs
@@ -32,6 +32,7 @@ use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::codes::*;
 use rustc_errors::{Applicability, Diag, ErrorGuaranteed};
 use rustc_hir::{self as hir, ExprKind};
+use rustc_infer::infer::DefineOpaqueTypes;
 use rustc_macros::{TypeFoldable, TypeVisitable};
 use rustc_middle::mir::Mutability;
 use rustc_middle::ty::adjustment::AllowTwoPhase;
@@ -152,12 +153,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 }
 
 #[derive(Copy, Clone, Debug)]
-pub enum CastError {
+enum CastError<'tcx> {
     ErrorGuaranteed(ErrorGuaranteed),
 
     CastToBool,
     CastToChar,
-    DifferingKinds,
+    DifferingKinds {
+        src_kind: PointerKind<'tcx>,
+        dst_kind: PointerKind<'tcx>,
+    },
     /// Cast of thin to fat raw ptr (e.g., `*const () as *const [u8]`).
     SizedUnsizedCast,
     IllegalCast,
@@ -177,7 +181,7 @@ pub enum CastError {
     ForeignNonExhaustiveAdt,
 }
 
-impl From<ErrorGuaranteed> for CastError {
+impl From<ErrorGuaranteed> for CastError<'_> {
     fn from(err: ErrorGuaranteed) -> Self {
         CastError::ErrorGuaranteed(err)
     }
@@ -251,7 +255,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
         }
     }
 
-    fn report_cast_error(&self, fcx: &FnCtxt<'a, 'tcx>, e: CastError) {
+    fn report_cast_error(&self, fcx: &FnCtxt<'a, 'tcx>, e: CastError<'tcx>) {
         match e {
             CastError::ErrorGuaranteed(_) => {
                 // an error has already been reported
@@ -303,10 +307,52 @@ impl<'a, 'tcx> CastCheck<'tcx> {
             CastError::IllegalCast => {
                 make_invalid_casting_error(self.span, self.expr_ty, self.cast_ty, fcx).emit();
             }
-            CastError::DifferingKinds => {
-                make_invalid_casting_error(self.span, self.expr_ty, self.cast_ty, fcx)
-                    .with_note("vtable kinds may not match")
-                    .emit();
+            CastError::DifferingKinds { src_kind, dst_kind } => {
+                let mut err =
+                    make_invalid_casting_error(self.span, self.expr_ty, self.cast_ty, fcx);
+
+                match (src_kind, dst_kind) {
+                    (PointerKind::VTable(_), PointerKind::VTable(_)) => {
+                        err.note("the trait objects may have different vtables");
+                    }
+                    (
+                        PointerKind::OfParam(_) | PointerKind::OfAlias(_),
+                        PointerKind::OfParam(_)
+                        | PointerKind::OfAlias(_)
+                        | PointerKind::VTable(_)
+                        | PointerKind::Length,
+                    )
+                    | (
+                        PointerKind::VTable(_) | PointerKind::Length,
+                        PointerKind::OfParam(_) | PointerKind::OfAlias(_),
+                    ) => {
+                        err.note("the pointers may have different metadata");
+                    }
+                    (PointerKind::VTable(_), PointerKind::Length)
+                    | (PointerKind::Length, PointerKind::VTable(_)) => {
+                        err.note("the pointers have different metadata");
+                    }
+                    (
+                        PointerKind::Thin,
+                        PointerKind::Thin
+                        | PointerKind::VTable(_)
+                        | PointerKind::Length
+                        | PointerKind::OfParam(_)
+                        | PointerKind::OfAlias(_),
+                    )
+                    | (
+                        PointerKind::VTable(_)
+                        | PointerKind::Length
+                        | PointerKind::OfParam(_)
+                        | PointerKind::OfAlias(_),
+                        PointerKind::Thin,
+                    )
+                    | (PointerKind::Length, PointerKind::Length) => {
+                        span_bug!(self.span, "unexpected cast error: {e:?}")
+                    }
+                }
+
+                err.emit();
             }
             CastError::CastToBool => {
                 let expr_ty = fcx.resolve_vars_if_possible(self.expr_ty);
@@ -670,7 +716,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
     /// Checks a cast, and report an error if one exists. In some cases, this
     /// can return Ok and create type errors in the fcx rather than returning
     /// directly. coercion-cast is handled in check instead of here.
-    fn do_check(&self, fcx: &FnCtxt<'a, 'tcx>) -> Result<CastKind, CastError> {
+    fn do_check(&self, fcx: &FnCtxt<'a, 'tcx>) -> Result<CastKind, CastError<'tcx>> {
         use rustc_middle::ty::cast::CastTy::*;
         use rustc_middle::ty::cast::IntTy::*;
 
@@ -798,27 +844,34 @@ impl<'a, 'tcx> CastCheck<'tcx> {
         fcx: &FnCtxt<'a, 'tcx>,
         m_src: ty::TypeAndMut<'tcx>,
         m_dst: ty::TypeAndMut<'tcx>,
-    ) -> Result<CastKind, CastError> {
+    ) -> Result<CastKind, CastError<'tcx>> {
         debug!("check_ptr_ptr_cast m_src={m_src:?} m_dst={m_dst:?}");
-        // ptr-ptr cast. vtables must match.
+        // ptr-ptr cast. metadata must match.
 
         let src_kind = fcx.tcx.erase_regions(fcx.pointer_kind(m_src.ty, self.span)?);
         let dst_kind = fcx.tcx.erase_regions(fcx.pointer_kind(m_dst.ty, self.span)?);
 
-        match (src_kind, dst_kind) {
-            // We can't cast if target pointer kind is unknown
-            (_, None) => Err(CastError::UnknownCastPtrKind),
-            // Cast to thin pointer is OK
-            (_, Some(PointerKind::Thin)) => Ok(CastKind::PtrPtrCast),
+        // We can't cast if target pointer kind is unknown
+        let Some(dst_kind) = dst_kind else {
+            return Err(CastError::UnknownCastPtrKind);
+        };
+
+        // Cast to thin pointer is OK
+        if dst_kind == PointerKind::Thin {
+            return Ok(CastKind::PtrPtrCast);
+        }
 
-            // We can't cast to fat pointer if source pointer kind is unknown
-            (None, _) => Err(CastError::UnknownExprPtrKind),
+        // We can't cast to fat pointer if source pointer kind is unknown
+        let Some(src_kind) = src_kind else {
+            return Err(CastError::UnknownCastPtrKind);
+        };
 
+        match (src_kind, dst_kind) {
             // thin -> fat? report invalid cast (don't complain about vtable kinds)
-            (Some(PointerKind::Thin), _) => Err(CastError::SizedUnsizedCast),
+            (PointerKind::Thin, _) => Err(CastError::SizedUnsizedCast),
 
             // trait object -> trait object? need to do additional checks
-            (Some(PointerKind::VTable(src_tty)), Some(PointerKind::VTable(dst_tty))) => {
+            (PointerKind::VTable(src_tty), PointerKind::VTable(dst_tty)) => {
                 match (src_tty.principal(), dst_tty.principal()) {
                     // A<dyn Src<...> + SrcAuto> -> B<dyn Dst<...> + DstAuto>. need to make sure
                     // - `Src` and `Dst` traits are the same
@@ -834,7 +887,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
                         // Note that trait upcasting goes through a different mechanism (`coerce_unsized`)
                         // and is unaffected by this check.
                         if src_principal.def_id() != dst_principal.def_id() {
-                            return Err(CastError::DifferingKinds);
+                            return Err(CastError::DifferingKinds { src_kind, dst_kind });
                         }
 
                         // We need to reconstruct trait object types.
@@ -860,7 +913,16 @@ impl<'a, 'tcx> CastCheck<'tcx> {
                         ));
 
                         // `dyn Src = dyn Dst`, this checks for matching traits/generics
-                        fcx.demand_eqtype(self.span, src_obj, dst_obj);
+                        // This is `demand_eqtype`, but inlined to give a better error.
+                        let cause = fcx.misc(self.span);
+                        if fcx
+                            .at(&cause, fcx.param_env)
+                            .eq(DefineOpaqueTypes::Yes, src_obj, dst_obj)
+                            .map(|infer_ok| fcx.register_infer_ok_obligations(infer_ok))
+                            .is_err()
+                        {
+                            return Err(CastError::DifferingKinds { src_kind, dst_kind });
+                        }
 
                         // Check that `SrcAuto` (+auto traits implied by `Src`) is a superset of `DstAuto`.
                         // Emit an FCW otherwise.
@@ -905,17 +967,17 @@ impl<'a, 'tcx> CastCheck<'tcx> {
 
                     // dyn Trait -> dyn Auto? should be ok, but we used to not allow it.
                     // FIXME: allow this
-                    (Some(_), None) => Err(CastError::DifferingKinds),
+                    (Some(_), None) => Err(CastError::DifferingKinds { src_kind, dst_kind }),
 
                     // dyn Auto -> dyn Trait? not ok.
-                    (None, Some(_)) => Err(CastError::DifferingKinds),
+                    (None, Some(_)) => Err(CastError::DifferingKinds { src_kind, dst_kind }),
                 }
             }
 
             // fat -> fat? metadata kinds must match
-            (Some(src_kind), Some(dst_kind)) if src_kind == dst_kind => Ok(CastKind::PtrPtrCast),
+            (src_kind, dst_kind) if src_kind == dst_kind => Ok(CastKind::PtrPtrCast),
 
-            (_, _) => Err(CastError::DifferingKinds),
+            (_, _) => Err(CastError::DifferingKinds { src_kind, dst_kind }),
         }
     }
 
@@ -923,7 +985,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
         &self,
         fcx: &FnCtxt<'a, 'tcx>,
         m_cast: ty::TypeAndMut<'tcx>,
-    ) -> Result<CastKind, CastError> {
+    ) -> Result<CastKind, CastError<'tcx>> {
         // fptr-ptr cast. must be to thin ptr
 
         match fcx.pointer_kind(m_cast.ty, self.span)? {
@@ -937,7 +999,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
         &self,
         fcx: &FnCtxt<'a, 'tcx>,
         m_expr: ty::TypeAndMut<'tcx>,
-    ) -> Result<CastKind, CastError> {
+    ) -> Result<CastKind, CastError<'tcx>> {
         // ptr-addr cast. must be from thin ptr
 
         match fcx.pointer_kind(m_expr.ty, self.span)? {
@@ -952,7 +1014,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
         fcx: &FnCtxt<'a, 'tcx>,
         m_expr: ty::TypeAndMut<'tcx>,
         m_cast: ty::TypeAndMut<'tcx>,
-    ) -> Result<CastKind, CastError> {
+    ) -> Result<CastKind, CastError<'tcx>> {
         // array-ptr-cast: allow mut-to-mut, mut-to-const, const-to-const
         if m_expr.mutbl >= m_cast.mutbl {
             if let ty::Array(ety, _) = m_expr.ty.kind() {
@@ -987,7 +1049,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
         &self,
         fcx: &FnCtxt<'a, 'tcx>,
         m_cast: TypeAndMut<'tcx>,
-    ) -> Result<CastKind, CastError> {
+    ) -> Result<CastKind, CastError<'tcx>> {
         // ptr-addr cast. pointer must be thin.
         match fcx.pointer_kind(m_cast.ty, self.span)? {
             None => Err(CastError::UnknownCastPtrKind),
diff --git a/tests/ui/cast/casts-differing-anon.stderr b/tests/ui/cast/casts-differing-anon.stderr
index 8ddd97137c30d..fc4882d2d2774 100644
--- a/tests/ui/cast/casts-differing-anon.stderr
+++ b/tests/ui/cast/casts-differing-anon.stderr
@@ -4,7 +4,7 @@ error[E0606]: casting `*mut impl Debug + ?Sized` as `*mut impl Debug + ?Sized` i
 LL |     b_raw = f_raw as *mut _;
    |             ^^^^^^^^^^^^^^^
    |
-   = note: vtable kinds may not match
+   = note: the pointers may have different metadata
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/cast/ptr-to-trait-obj-different-args.rs b/tests/ui/cast/ptr-to-trait-obj-different-args.rs
index c6038cfe86401..bb103f789f55b 100644
--- a/tests/ui/cast/ptr-to-trait-obj-different-args.rs
+++ b/tests/ui/cast/ptr-to-trait-obj-different-args.rs
@@ -18,14 +18,14 @@ fn main() {
     let b: *const dyn B = a as _; //~ error: casting `*const dyn A` as `*const dyn B` is invalid
 
     let x: *const dyn Trait<X> = &();
-    let y: *const dyn Trait<Y> = x as _; //~ error: mismatched types
+    let y: *const dyn Trait<Y> = x as _; //~ error: casting `*const dyn Trait<X>` as `*const dyn Trait<Y>` is invalid
 
     _ = (b, y);
 }
 
 fn generic<T>(x: *const dyn Trait<X>, t: *const dyn Trait<T>) {
-    let _: *const dyn Trait<T> = x as _; //~ error: mismatched types
-    let _: *const dyn Trait<X> = t as _; //~ error: mismatched types
+    let _: *const dyn Trait<T> = x as _; //~ error: casting `*const (dyn Trait<X> + 'static)` as `*const dyn Trait<T>` is invalid
+    let _: *const dyn Trait<X> = t as _; //~ error: casting `*const (dyn Trait<T> + 'static)` as `*const dyn Trait<X>` is invalid
 }
 
 trait Assocked {
@@ -33,5 +33,5 @@ trait Assocked {
 }
 
 fn change_assoc(x: *mut dyn Assocked<Assoc = u8>) -> *mut dyn Assocked<Assoc = u32> {
-    x as _ //~ error: mismatched types
+    x as _ //~ error: casting `*mut (dyn Assocked<Assoc = u8> + 'static)` as `*mut (dyn Assocked<Assoc = u32> + 'static)` is invalid
 }
diff --git a/tests/ui/cast/ptr-to-trait-obj-different-args.stderr b/tests/ui/cast/ptr-to-trait-obj-different-args.stderr
index 8e60ca42f0a52..e571a43959ffd 100644
--- a/tests/ui/cast/ptr-to-trait-obj-different-args.stderr
+++ b/tests/ui/cast/ptr-to-trait-obj-different-args.stderr
@@ -4,53 +4,40 @@ error[E0606]: casting `*const dyn A` as `*const dyn B` is invalid
 LL |     let b: *const dyn B = a as _;
    |                           ^^^^^^
    |
-   = note: vtable kinds may not match
+   = note: the trait objects may have different vtables
 
-error[E0308]: mismatched types
+error[E0606]: casting `*const dyn Trait<X>` as `*const dyn Trait<Y>` is invalid
   --> $DIR/ptr-to-trait-obj-different-args.rs:21:34
    |
 LL |     let y: *const dyn Trait<Y> = x as _;
-   |                                  ^^^^^^ expected `X`, found `Y`
+   |                                  ^^^^^^
    |
-   = note: expected trait object `dyn Trait<X>`
-              found trait object `dyn Trait<Y>`
-   = help: `dyn Trait<Y>` implements `Trait` so you could box the found value and coerce it to the trait object `Box<dyn Trait>`, you will have to change the expected type as well
+   = note: the trait objects may have different vtables
 
-error[E0308]: mismatched types
+error[E0606]: casting `*const (dyn Trait<X> + 'static)` as `*const dyn Trait<T>` is invalid
   --> $DIR/ptr-to-trait-obj-different-args.rs:27:34
    |
-LL | fn generic<T>(x: *const dyn Trait<X>, t: *const dyn Trait<T>) {
-   |            - found this type parameter
 LL |     let _: *const dyn Trait<T> = x as _;
-   |                                  ^^^^^^ expected `X`, found type parameter `T`
+   |                                  ^^^^^^
    |
-   = note: expected trait object `dyn Trait<X>`
-              found trait object `dyn Trait<T>`
-   = help: `dyn Trait<T>` implements `Trait` so you could box the found value and coerce it to the trait object `Box<dyn Trait>`, you will have to change the expected type as well
+   = note: the trait objects may have different vtables
 
-error[E0308]: mismatched types
+error[E0606]: casting `*const (dyn Trait<T> + 'static)` as `*const dyn Trait<X>` is invalid
   --> $DIR/ptr-to-trait-obj-different-args.rs:28:34
    |
-LL | fn generic<T>(x: *const dyn Trait<X>, t: *const dyn Trait<T>) {
-   |            - expected this type parameter
-LL |     let _: *const dyn Trait<T> = x as _;
 LL |     let _: *const dyn Trait<X> = t as _;
-   |                                  ^^^^^^ expected type parameter `T`, found `X`
+   |                                  ^^^^^^
    |
-   = note: expected trait object `dyn Trait<T>`
-              found trait object `dyn Trait<X>`
-   = help: `dyn Trait<X>` implements `Trait` so you could box the found value and coerce it to the trait object `Box<dyn Trait>`, you will have to change the expected type as well
+   = note: the trait objects may have different vtables
 
-error[E0308]: mismatched types
+error[E0606]: casting `*mut (dyn Assocked<Assoc = u8> + 'static)` as `*mut (dyn Assocked<Assoc = u32> + 'static)` is invalid
   --> $DIR/ptr-to-trait-obj-different-args.rs:36:5
    |
 LL |     x as _
-   |     ^^^^^^ expected `u8`, found `u32`
+   |     ^^^^^^
    |
-   = note: expected trait object `dyn Assocked<Assoc = u8>`
-              found trait object `dyn Assocked<Assoc = u32>`
+   = note: the trait objects may have different vtables
 
 error: aborting due to 5 previous errors
 
-Some errors have detailed explanations: E0308, E0606.
-For more information about an error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0606`.
diff --git a/tests/ui/cast/ptr-to-trait-obj-wrap-upcast.stderr b/tests/ui/cast/ptr-to-trait-obj-wrap-upcast.stderr
index 38c8ba96bc5b7..5687aba625ff7 100644
--- a/tests/ui/cast/ptr-to-trait-obj-wrap-upcast.stderr
+++ b/tests/ui/cast/ptr-to-trait-obj-wrap-upcast.stderr
@@ -4,7 +4,7 @@ error[E0606]: casting `*const (dyn Sub + 'static)` as `*const Wrapper<dyn Super>
 LL |     ptr as _
    |     ^^^^^^^^
    |
-   = note: vtable kinds may not match
+   = note: the trait objects may have different vtables
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/mismatched_types/cast-rfc0401.stderr b/tests/ui/mismatched_types/cast-rfc0401.stderr
index 142a52aef13d0..3d12ba9899bc5 100644
--- a/tests/ui/mismatched_types/cast-rfc0401.stderr
+++ b/tests/ui/mismatched_types/cast-rfc0401.stderr
@@ -4,7 +4,7 @@ error[E0606]: casting `*const U` as `*const V` is invalid
 LL |     u as *const V
    |     ^^^^^^^^^^^^^
    |
-   = note: vtable kinds may not match
+   = note: the pointers may have different metadata
 
 error[E0606]: casting `*const U` as `*const str` is invalid
   --> $DIR/cast-rfc0401.rs:8:5
@@ -12,7 +12,7 @@ error[E0606]: casting `*const U` as `*const str` is invalid
 LL |     u as *const str
    |     ^^^^^^^^^^^^^^^
    |
-   = note: vtable kinds may not match
+   = note: the pointers may have different metadata
 
 error[E0609]: no field `f` on type `fn() {main}`
   --> $DIR/cast-rfc0401.rs:65:18
@@ -208,7 +208,7 @@ error[E0606]: casting `*const dyn Foo` as `*const [u16]` is invalid
 LL |     let _ = cf as *const [u16];
    |             ^^^^^^^^^^^^^^^^^^
    |
-   = note: vtable kinds may not match
+   = note: the pointers have different metadata
 
 error[E0606]: casting `*const dyn Foo` as `*const dyn Bar` is invalid
   --> $DIR/cast-rfc0401.rs:69:13
@@ -216,7 +216,7 @@ error[E0606]: casting `*const dyn Foo` as `*const dyn Bar` is invalid
 LL |     let _ = cf as *const dyn Bar;
    |             ^^^^^^^^^^^^^^^^^^^^
    |
-   = note: vtable kinds may not match
+   = note: the trait objects may have different vtables
 
 error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
   --> $DIR/cast-rfc0401.rs:53:13
diff --git a/tests/ui/traits/upcast_soundness_bug.rs b/tests/ui/traits/upcast_soundness_bug.rs
index 5eaa58f7efe7f..0ddae1d1417c7 100644
--- a/tests/ui/traits/upcast_soundness_bug.rs
+++ b/tests/ui/traits/upcast_soundness_bug.rs
@@ -57,7 +57,7 @@ pub fn user2() -> &'static dyn Trait<u8, u16> {
 fn main() {
     let p: *const dyn Trait<u8, u8> = &();
     let p = p as *const dyn Trait<u8, u16>; // <- this is bad!
-    //~^ error: mismatched types
+    //~^ error: casting `*const dyn Trait<u8, u8>` as `*const dyn Trait<u8, u16>` is invalid
     let p = p as *const dyn Super<u16>; // <- this upcast accesses improper vtable entry
     // accessing from L__unnamed_2 the position for the 'Super<u16> vtable (pointer)',
     // thus reading 'null pointer for missing_method'
diff --git a/tests/ui/traits/upcast_soundness_bug.stderr b/tests/ui/traits/upcast_soundness_bug.stderr
index 5864abcdb41f5..19d1a5e5926e0 100644
--- a/tests/ui/traits/upcast_soundness_bug.stderr
+++ b/tests/ui/traits/upcast_soundness_bug.stderr
@@ -1,13 +1,11 @@
-error[E0308]: mismatched types
+error[E0606]: casting `*const dyn Trait<u8, u8>` as `*const dyn Trait<u8, u16>` is invalid
   --> $DIR/upcast_soundness_bug.rs:59:13
    |
 LL |     let p = p as *const dyn Trait<u8, u16>; // <- this is bad!
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `u8`, found `u16`
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: expected trait object `dyn Trait<u8, u8>`
-              found trait object `dyn Trait<u8, u16>`
-   = help: `dyn Trait<u8, u16>` implements `Trait` so you could box the found value and coerce it to the trait object `Box<dyn Trait>`, you will have to change the expected type as well
+   = note: the trait objects may have different vtables
 
 error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0606`.

From b62e72ce8c31bbfd028136570a5e46bee233d4f3 Mon Sep 17 00:00:00 2001
From: Lukas Markeffsky <@>
Date: Sun, 15 Sep 2024 23:26:51 +0200
Subject: [PATCH 14/14] update doc comment

---
 compiler/rustc_middle/src/mir/syntax.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index bba3aee820ab2..ae75f2d4187ba 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -579,7 +579,8 @@ pub struct CopyNonOverlapping<'tcx> {
     pub count: Operand<'tcx>,
 }
 
-/// Represents how a [`TerminatorKind::Call`] was constructed, used for diagnostics.
+/// Represents how a [`TerminatorKind::Call`] was constructed.
+/// Used only for diagnostics.
 #[derive(Clone, Copy, TyEncodable, TyDecodable, Debug, PartialEq, Hash, HashStable)]
 #[derive(TypeFoldable, TypeVisitable)]
 pub enum CallSource {
@@ -1419,7 +1420,8 @@ pub enum CastKind {
     Transmute,
 }
 
-/// Represents how a [`CastKind::PointerCoercion`] was constructed, used for diagnostics.
+/// Represents how a [`CastKind::PointerCoercion`] was constructed.
+/// Used only for diagnostics.
 #[derive(Clone, Copy, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
 pub enum CoercionSource {
     /// The coercion was manually written by the user with an `as` cast.