diag: Suppress .clone() suggestion inside derive macro expansions

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -28,7 +28,7 @@ use rustc_middle::ty::{
 use rustc_mir_dataflow::move_paths::{InitKind, MoveOutIndex, MovePathIndex};
 use rustc_span::def_id::{DefId, LocalDefId};
 use rustc_span::hygiene::DesugaringKind;
-use rustc_span::{BytePos, Ident, Span, Symbol, kw, sym};
+use rustc_span::{BytePos, ExpnKind, Ident, MacroKind, Span, Symbol, kw, sym};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::error_reporting::traits::FindExprBySpan;
 use rustc_trait_selection::error_reporting::traits::call_kind::CallKind;
@@ -1438,6 +1438,12 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         expr: &hir::Expr<'_>,
     ) -> bool {
         let tcx = self.infcx.tcx;
+
+        // Don't suggest `.clone()` in a derive macro expansion.
+        if let ExpnKind::Macro(MacroKind::Derive, _) = self.body.span.ctxt().outer_expn_data().kind
+        {
+            return false;
+        }
         if let Some(_) = self.clone_on_reference(expr) {
             // Avoid redundant clone suggestion already suggested in `explain_captures`.
             // See `tests/ui/moves/needs-clone-through-deref.rs`

tests/ui/derives/deriving-with-repr-packed-move-errors.stderr

@@ -7,10 +7,6 @@ LL | struct StructA(String);
    |                ^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
    |
    = note: `#[derive(Debug)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
-help: consider cloning the value if the performance cost is acceptable
-   |
-LL | struct StructA(String.clone());
-   |                      ++++++++
 
 error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:13:16
@@ -21,10 +17,6 @@ LL | struct StructA(String);
    |                ^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
    |
    = note: `#[derive(PartialEq)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
-help: consider cloning the value if the performance cost is acceptable
-   |
-LL | struct StructA(String.clone());
-   |                      ++++++++
 
 error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:13:16
@@ -36,10 +28,6 @@ LL | struct StructA(String);
    |
    = note: `#[derive(PartialEq)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-help: consider cloning the value if the performance cost is acceptable
-   |
-LL | struct StructA(String.clone());
-   |                      ++++++++
 
 error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:13:16
@@ -50,10 +38,6 @@ LL | struct StructA(String);
    |                ^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
    |
    = note: `#[derive(PartialOrd)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
-help: consider cloning the value if the performance cost is acceptable
-   |
-LL | struct StructA(String.clone());
-   |                      ++++++++
 
 error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:13:16
@@ -65,10 +49,6 @@ LL | struct StructA(String);
    |
    = note: `#[derive(PartialOrd)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-help: consider cloning the value if the performance cost is acceptable
-   |
-LL | struct StructA(String.clone());
-   |                      ++++++++
 
 error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:13:16
@@ -79,10 +59,6 @@ LL | struct StructA(String);
    |                ^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
    |
    = note: `#[derive(Ord)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
-help: consider cloning the value if the performance cost is acceptable
-   |
-LL | struct StructA(String.clone());
-   |                      ++++++++
 
 error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:13:16
@@ -94,10 +70,6 @@ LL | struct StructA(String);
    |
    = note: `#[derive(Ord)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-help: consider cloning the value if the performance cost is acceptable
-   |
-LL | struct StructA(String.clone());
-   |                      ++++++++
 
 error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:13:16
@@ -108,10 +80,6 @@ LL | struct StructA(String);
    |                ^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
    |
    = note: `#[derive(Hash)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
-help: consider cloning the value if the performance cost is acceptable
-   |
-LL | struct StructA(String.clone());
-   |                      ++++++++
 
 error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:13:16
@@ -122,10 +90,6 @@ LL | struct StructA(String);
    |                ^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
    |
    = note: `#[derive(Clone)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
-help: consider cloning the value if the performance cost is acceptable
-   |
-LL | struct StructA(String.clone());
-   |                      ++++++++
 
 error[E0507]: cannot move out of `self` which is behind a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:28:9

tests/ui/derives/deriving-with-repr-packed-no-clone-suggestion.rs

@@ -0,0 +1,9 @@
+// Test for https://github.com/rust-lang/rust/issues/153126
+
+#[repr(packed, C)]
+#[derive(PartialEq)]
+struct Thing(u8, String);
+//~^ ERROR cannot move out of a shared reference
+//~| ERROR cannot move out of a shared reference
+
+fn main() {}

tests/ui/derives/deriving-with-repr-packed-no-clone-suggestion.stderr

@@ -0,0 +1,24 @@
+error[E0507]: cannot move out of a shared reference
+  --> $DIR/deriving-with-repr-packed-no-clone-suggestion.rs:5:18
+   |
+LL | #[derive(PartialEq)]
+   |          --------- in this derive macro expansion
+LL | struct Thing(u8, String);
+   |                  ^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
+   |
+   = note: `#[derive(PartialEq)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
+
+error[E0507]: cannot move out of a shared reference
+  --> $DIR/deriving-with-repr-packed-no-clone-suggestion.rs:5:18
+   |
+LL | #[derive(PartialEq)]
+   |          --------- in this derive macro expansion
+LL | struct Thing(u8, String);
+   |                  ^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
+   |
+   = note: `#[derive(PartialEq)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0507`.