Auto merge of #108920 - matthiaskrgr:rollup-qrr9a0u, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - #108754 (Retry `pred_known_to_hold_modulo_regions` with fulfillment if ambiguous)
 - #108759 (1.41.1 supported 32-bit Apple targets)
 - #108839 (Canonicalize root var when making response from new solver)
 - #108856 (Remove DropAndReplace terminator)
 - #108882 (Tweak E0740)
 - #108898 (Set `LIBC_CHECK_CFG=1` when building Rust code in bootstrap)
 - #108911 (Improve rustdoc-gui/tester.js code a bit)
 - #108916 (Remove an unused return value in `rustc_hir_typeck`)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

RELEASES.md

@@ -3861,6 +3861,8 @@ Version 1.41.1 (2020-02-27)
 * [Always check types of static items][69145]
 * [Always check lifetime bounds of `Copy` impls][69145]
 * [Fix miscompilation in callers of `Layout::repeat`][69225]
+* [Rust 1.41.0 was announced as the last Rust release with tier 1 or tier 2 support for 32-bit Apple targets][apple-32bit-drop].
+  That announcement did not expect a patch release. 1.41.1 also includes release binaries for these targets.
 
 [69225]: https://github.com/rust-lang/rust/issues/69225
 [69145]: https://github.com/rust-lang/rust/pull/69145
@@ -3953,7 +3955,7 @@ Misc
 Compatibility Notes
 -------------------
 
-- [As previously announced 1.41.0 will be the last tier 1 release for 32-bit
+- [As previously announced 1.41 will be the last tier 1 release for 32-bit
   Apple targets.][apple-32bit-drop] This means that the source code is still
   available to build, but the targets are no longer being tested and release
   binaries for those platforms will no longer be distributed by the Rust project.

compiler/rustc_borrowck/src/invalidation.rs

@@ -118,15 +118,6 @@ impl<'cx, 'tcx> Visitor<'tcx> for InvalidationGenerator<'cx, 'tcx> {
                     LocalMutationIsAllowed::Yes,
                 );
             }
-            TerminatorKind::DropAndReplace {
-                place: drop_place,
-                value: new_value,
-                target: _,
-                unwind: _,
-            } => {
-                self.mutate_place(location, *drop_place, Deep);
-                self.consume_operand(location, new_value);
-            }
             TerminatorKind::Call {
                 func,
                 args,

compiler/rustc_borrowck/src/lib.rs

@@ -743,15 +743,6 @@ impl<'cx, 'tcx> rustc_mir_dataflow::ResultsVisitor<'cx, 'tcx> for MirBorrowckCtx
                     flow_state,
                 );
             }
-            TerminatorKind::DropAndReplace {
-                place: drop_place,
-                value: new_value,
-                target: _,
-                unwind: _,
-            } => {
-                self.mutate_place(loc, (*drop_place, span), Deep, flow_state);
-                self.consume_operand(loc, (new_value, span), flow_state);
-            }
             TerminatorKind::Call {
                 func,
                 args,
@@ -866,7 +857,6 @@ impl<'cx, 'tcx> rustc_mir_dataflow::ResultsVisitor<'cx, 'tcx> for MirBorrowckCtx
             | TerminatorKind::Assert { .. }
             | TerminatorKind::Call { .. }
             | TerminatorKind::Drop { .. }
-            | TerminatorKind::DropAndReplace { .. }
             | TerminatorKind::FalseEdge { real_target: _, imaginary_target: _ }
             | TerminatorKind::FalseUnwind { real_target: _, unwind: _ }
             | TerminatorKind::Goto { .. }

compiler/rustc_borrowck/src/type_check/liveness/trace.rs

@@ -435,8 +435,7 @@ impl<'me, 'typeck, 'flow, 'tcx> LivenessResults<'me, 'typeck, 'flow, 'tcx> {
         //
         // What we *actually* generate is a store to a temporary
         // for the call (`TMP = call()...`) and then a
-        // `DropAndReplace` to swap that with `X`
-        // (`DropAndReplace` has very particular semantics).
+        // `Drop(X)` followed by `X = TMP`  to swap that with `X`.
     }
 }
 

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1312,24 +1312,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 // no checks needed for these
             }
 
-            TerminatorKind::DropAndReplace { place, value, target: _, unwind: _ } => {
-                let place_ty = place.ty(body, tcx).ty;
-                let rv_ty = value.ty(body, tcx);
-
-                let locations = term_location.to_locations();
-                if let Err(terr) =
-                    self.sub_types(rv_ty, place_ty, locations, ConstraintCategory::Assignment)
-                {
-                    span_mirbug!(
-                        self,
-                        term,
-                        "bad DropAndReplace ({:?} = {:?}): {:?}",
-                        place_ty,
-                        rv_ty,
-                        terr
-                    );
-                }
-            }
             TerminatorKind::SwitchInt { discr, .. } => {
                 self.check_operand(discr, term_location);
 
@@ -1629,7 +1611,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             }
             TerminatorKind::Unreachable => {}
             TerminatorKind::Drop { target, unwind, .. }
-            | TerminatorKind::DropAndReplace { target, unwind, .. }
             | TerminatorKind::Assert { target, cleanup: unwind, .. } => {
                 self.assert_iscleanup(body, block_data, target, is_cleanup);
                 if let Some(unwind) = unwind {

compiler/rustc_borrowck/src/used_muts.rs

@@ -71,9 +71,6 @@ impl<'visit, 'cx, 'tcx> Visitor<'tcx> for GatherUsedMutsVisitor<'visit, 'cx, 'tc
             TerminatorKind::Call { destination, .. } => {
                 self.remove_never_initialized_mut_locals(*destination);
             }
-            TerminatorKind::DropAndReplace { place, .. } => {
-                self.remove_never_initialized_mut_locals(*place);
-            }
             _ => {}
         }
 

compiler/rustc_codegen_cranelift/src/base.rs

@@ -499,7 +499,6 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
             TerminatorKind::Yield { .. }
             | TerminatorKind::FalseEdge { .. }
             | TerminatorKind::FalseUnwind { .. }
-            | TerminatorKind::DropAndReplace { .. }
             | TerminatorKind::GeneratorDrop => {
                 bug!("shouldn't exist at codegen {:?}", bb_data.terminator());
             }

compiler/rustc_codegen_cranelift/src/constant.rs

@@ -543,8 +543,7 @@ pub(crate) fn mir_operand_get_const_val<'tcx>(
                     | TerminatorKind::Unreachable
                     | TerminatorKind::Drop { .. }
                     | TerminatorKind::Assert { .. } => {}
-                    TerminatorKind::DropAndReplace { .. }
-                    | TerminatorKind::Yield { .. }
+                    TerminatorKind::Yield { .. }
                     | TerminatorKind::GeneratorDrop
                     | TerminatorKind::FalseEdge { .. }
                     | TerminatorKind::FalseUnwind { .. } => unreachable!(),

compiler/rustc_codegen_ssa/src/mir/analyze.rs

@@ -295,7 +295,6 @@ pub fn cleanup_kinds(mir: &mir::Body<'_>) -> IndexVec<mir::BasicBlock, CleanupKi
                 TerminatorKind::Call { cleanup: unwind, .. }
                 | TerminatorKind::InlineAsm { cleanup: unwind, .. }
                 | TerminatorKind::Assert { cleanup: unwind, .. }
-                | TerminatorKind::DropAndReplace { unwind, .. }
                 | TerminatorKind::Drop { unwind, .. } => {
                     if let Some(unwind) = unwind {
                         debug!(

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -1305,10 +1305,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     mergeable_succ(),
                 ),
 
-            mir::TerminatorKind::DropAndReplace { .. } => {
-                bug!("undesugared DropAndReplace in codegen: {:?}", terminator);
-            }
-
             mir::TerminatorKind::Call {
                 ref func,
                 ref args,

compiler/rustc_const_eval/src/interpret/terminator.rs

@@ -171,11 +171,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             Unreachable => throw_ub!(Unreachable),
 
             // These should never occur for MIR we actually run.
-            DropAndReplace { .. }
-            | FalseEdge { .. }
-            | FalseUnwind { .. }
-            | Yield { .. }
-            | GeneratorDrop => span_bug!(
+            FalseEdge { .. } | FalseUnwind { .. } | Yield { .. } | GeneratorDrop => span_bug!(
                 terminator.source_info.span,
                 "{:#?} should have been eliminated by MIR pass",
                 terminator.kind

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -985,8 +985,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
 
             // Forbid all `Drop` terminators unless the place being dropped is a local with no
             // projections that cannot be `NeedsNonConstDrop`.
-            TerminatorKind::Drop { place: dropped_place, .. }
-            | TerminatorKind::DropAndReplace { place: dropped_place, .. } => {
+            TerminatorKind::Drop { place: dropped_place, .. } => {
                 // If we are checking live drops after drop-elaboration, don't emit duplicate
                 // errors here.
                 if super::post_drop_elaboration::checking_enabled(self.ccx) {

compiler/rustc_const_eval/src/transform/check_consts/post_drop_elaboration.rs

@@ -80,8 +80,7 @@ impl<'tcx> Visitor<'tcx> for CheckLiveDrops<'_, 'tcx> {
         trace!("visit_terminator: terminator={:?} location={:?}", terminator, location);
 
         match &terminator.kind {
-            mir::TerminatorKind::Drop { place: dropped_place, .. }
-            | mir::TerminatorKind::DropAndReplace { place: dropped_place, .. } => {
+            mir::TerminatorKind::Drop { place: dropped_place, .. } => {
                 let dropped_ty = dropped_place.ty(self.body, self.tcx).ty;
                 if !NeedsNonConstDrop::in_any_value_of_ty(self.ccx, dropped_ty) {
                     // Instead of throwing a bug, we just return here. This is because we have to

compiler/rustc_const_eval/src/transform/check_consts/resolver.rs

@@ -222,23 +222,8 @@ where
         // The effect of assignment to the return place in `TerminatorKind::Call` is not applied
         // here; that occurs in `apply_call_return_effect`.
 
-        if let mir::TerminatorKind::DropAndReplace { value, place, .. } = &terminator.kind {
-            let qualif = qualifs::in_operand::<Q, _>(
-                self.ccx,
-                &mut |l| self.state.qualif.contains(l),
-                value,
-            );
-
-            if !place.is_indirect() {
-                self.assign_qualif_direct(place, qualif);
-            }
-        }
-
         // We ignore borrow on drop because custom drop impls are not allowed in consts.
         // FIXME: Reconsider if accounting for borrows in drops is necessary for const drop.
-
-        // We need to assign qualifs to the dropped location before visiting the operand that
-        // replaces it since qualifs can be cleared on move.
         self.super_terminator(terminator, location);
     }
 }

compiler/rustc_const_eval/src/transform/validate.rs

@@ -846,18 +846,6 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                     self.check_edge(location, *unwind, EdgeKind::Unwind);
                 }
             }
-            TerminatorKind::DropAndReplace { target, unwind, .. } => {
-                if self.mir_phase >= MirPhase::Runtime(RuntimePhase::Initial) {
-                    self.fail(
-                        location,
-                        "`DropAndReplace` should have been removed during drop elaboration",
-                    );
-                }
-                self.check_edge(location, *target, EdgeKind::Normal);
-                if let Some(unwind) = unwind {
-                    self.check_edge(location, *unwind, EdgeKind::Unwind);
-                }
-            }
             TerminatorKind::Call { func, args, destination, target, cleanup, .. } => {
                 let func_ty = func.ty(&self.body.local_decls, self.tcx);
                 match func_ty.kind() {

compiler/rustc_hir_analysis/locales/en-US.ftl

@@ -163,3 +163,10 @@ hir_analysis_pass_to_variadic_function = can't pass `{$ty}` to variadic function
     .help = cast the value to `{$cast_ty}`
 
 hir_analysis_cast_thin_pointer_to_fat_pointer = cannot cast thin pointer `{$expr_ty}` to fat pointer `{$cast_ty}`
+
+hir_analysis_invalid_union_field =
+    field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union
+    .note = union fields must not have drop side-effects, which is currently enforced via either `Copy` or `ManuallyDrop<...>`
+
+hir_analysis_invalid_union_field_sugg =
+    wrap the field type in `ManuallyDrop<...>`

compiler/rustc_hir_analysis/src/check/check.rs

@@ -1,5 +1,5 @@
 use crate::check::intrinsicck::InlineAsmCtxt;
-use crate::errors::LinkageType;
+use crate::errors::{self, LinkageType};
 
 use super::compare_impl_item::check_type_bounds;
 use super::compare_impl_item::{compare_impl_method, compare_impl_ty};
@@ -114,9 +114,11 @@ fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: LocalDefId) -> b
                     allowed_union_field(*elem, tcx, param_env)
                 }
                 _ => {
-                    // Fallback case: allow `ManuallyDrop` and things that are `Copy`.
+                    // Fallback case: allow `ManuallyDrop` and things that are `Copy`,
+                    // also no need to report an error if the type is unresolved.
                     ty.ty_adt_def().is_some_and(|adt_def| adt_def.is_manually_drop())
                         || ty.is_copy_modulo_regions(tcx, param_env)
+                        || ty.references_error()
                 }
             }
         }
@@ -131,26 +133,14 @@ fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: LocalDefId) -> b
                     Some(Node::Field(field)) => (field.span, field.ty.span),
                     _ => unreachable!("mir field has to correspond to hir field"),
                 };
-                struct_span_err!(
-                    tcx.sess,
+                tcx.sess.emit_err(errors::InvalidUnionField {
                     field_span,
-                    E0740,
-                    "unions cannot contain fields that may need dropping"
-                )
-                .note(
-                    "a type is guaranteed not to need dropping \
-                    when it implements `Copy`, or when it is the special `ManuallyDrop<_>` type",
-                )
-                .multipart_suggestion_verbose(
-                    "when the type does not implement `Copy`, \
-                    wrap it inside a `ManuallyDrop<_>` and ensure it is manually dropped",
-                    vec![
-                        (ty_span.shrink_to_lo(), "std::mem::ManuallyDrop<".into()),
-                        (ty_span.shrink_to_hi(), ">".into()),
-                    ],
-                    Applicability::MaybeIncorrect,
-                )
-                .emit();
+                    sugg: errors::InvalidUnionFieldSuggestion {
+                        lo: ty_span.shrink_to_lo(),
+                        hi: ty_span.shrink_to_hi(),
+                    },
+                    note: (),
+                });
                 return false;
             } else if field_ty.needs_drop(tcx, param_env) {
                 // This should never happen. But we can get here e.g. in case of name resolution errors.

compiler/rustc_hir_analysis/src/errors.rs

@@ -5,7 +5,7 @@ use rustc_errors::{
     error_code, Applicability, DiagnosticBuilder, ErrorGuaranteed, Handler, IntoDiagnostic,
     MultiSpan,
 };
-use rustc_macros::Diagnostic;
+use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_middle::ty::Ty;
 use rustc_span::{symbol::Ident, Span, Symbol};
 
@@ -430,3 +430,23 @@ pub(crate) struct CastThinPointerToFatPointer<'tcx> {
     pub expr_ty: Ty<'tcx>,
     pub cast_ty: String,
 }
+
+#[derive(Diagnostic)]
+#[diag(hir_analysis_invalid_union_field, code = "E0740")]
+pub(crate) struct InvalidUnionField {
+    #[primary_span]
+    pub field_span: Span,
+    #[subdiagnostic]
+    pub sugg: InvalidUnionFieldSuggestion,
+    #[note]
+    pub note: (),
+}
+
+#[derive(Subdiagnostic)]
+#[multipart_suggestion(hir_analysis_invalid_union_field_sugg, applicability = "machine-applicable")]
+pub(crate) struct InvalidUnionFieldSuggestion {
+    #[suggestion_part(code = "std::mem::ManuallyDrop<")]
+    pub lo: Span,
+    #[suggestion_part(code = ">")]
+    pub hi: Span,
+}

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -301,16 +301,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         span: Span,
         def_id: DefId,
         substs: SubstsRef<'tcx>,
-    ) -> (ty::InstantiatedPredicates<'tcx>, Vec<Span>) {
+    ) -> ty::InstantiatedPredicates<'tcx> {
         let bounds = self.tcx.predicates_of(def_id);
-        let spans: Vec<Span> = bounds.predicates.iter().map(|(_, span)| *span).collect();
         let result = bounds.instantiate(self.tcx, substs);
         let result = self.normalize(span, result);
-        debug!(
-            "instantiate_bounds(bounds={:?}, substs={:?}) = {:?}, {:?}",
-            bounds, substs, result, spans,
-        );
-        (result, spans)
+        debug!("instantiate_bounds(bounds={:?}, substs={:?}) = {:?}", bounds, substs, result);
+        result
     }
 
     pub(in super::super) fn normalize<T>(&self, span: Span, value: T) -> T
@@ -1389,7 +1385,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
             _ => false,
         };
-        let (bounds, _) = self.instantiate_bounds(span, def_id, &substs);
+        let bounds = self.instantiate_bounds(span, def_id, &substs);
 
         for mut obligation in traits::predicates_for_generics(
             |idx, predicate_span| {

compiler/rustc_infer/src/infer/canonical/canonicalizer.rs

@@ -374,9 +374,18 @@ impl<'cx, 'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'cx, 'tcx> {
         }
     }
 
-    fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
+    fn fold_ty(&mut self, mut t: Ty<'tcx>) -> Ty<'tcx> {
         match *t.kind() {
-            ty::Infer(ty::TyVar(vid)) => {
+            ty::Infer(ty::TyVar(mut vid)) => {
+                // We need to canonicalize the *root* of our ty var.
+                // This is so that our canonical response correctly reflects
+                // any equated inference vars correctly!
+                let root_vid = self.infcx.root_var(vid);
+                if root_vid != vid {
+                    t = self.infcx.tcx.mk_ty_var(root_vid);
+                    vid = root_vid;
+                }
+
                 debug!("canonical: type var found with vid {:?}", vid);
                 match self.infcx.probe_ty_var(vid) {
                     // `t` could be a float / int variable; canonicalize that instead.
@@ -467,9 +476,18 @@ impl<'cx, 'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'cx, 'tcx> {
         }
     }
 
-    fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
+    fn fold_const(&mut self, mut ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
         match ct.kind() {
-            ty::ConstKind::Infer(InferConst::Var(vid)) => {
+            ty::ConstKind::Infer(InferConst::Var(mut vid)) => {
+                // We need to canonicalize the *root* of our const var.
+                // This is so that our canonical response correctly reflects
+                // any equated inference vars correctly!
+                let root_vid = self.infcx.root_const_var(vid);
+                if root_vid != vid {
+                    ct = self.infcx.tcx.mk_const(ty::InferConst::Var(root_vid), ct.ty());
+                    vid = root_vid;
+                }
+
                 debug!("canonical: const var found with vid {:?}", vid);
                 match self.infcx.probe_const_var(vid) {
                     Ok(c) => {