Auto merge of #94105 - 5225225:destabilise-entry-insert, r=Mark-Simulacrum

[rust.git] / compiler / rustc_typeck / src / check / check.rs

diff --git a/compiler/rustc_typeck/src/check/check.rs b/compiler/rustc_typeck/src/check/check.rs
index 27c8a1978355754b1a014eee54da6a207f78f58b..1650a62f79f29cc878bba3736c485fd833c489ff 100644 (file)
--- a/compiler/rustc_typeck/src/check/check.rs
+++ b/compiler/rustc_typeck/src/check/check.rs
@@ -382,12 +382,17 @@ fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: LocalDefId) -> b
                     tcx.sess,
                     field_span,
                     E0740,
-                    "unions may not contain fields that need dropping"
+                    "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(
-                    "wrap the type with `std::mem::ManuallyDrop` and ensure it is manually dropped",
+                    "when the type does not implement `Copy`, \
+                    wrap it inside a `ManuallyDrop<_>` and ensure it is manually dropped",
                     vec![
-                        (ty_span.shrink_to_lo(), format!("std::mem::ManuallyDrop<")),
+                        (ty_span.shrink_to_lo(), "std::mem::ManuallyDrop<".into()),
                         (ty_span.shrink_to_hi(), ">".into()),
                     ],
                     Applicability::MaybeIncorrect,
@@ -540,8 +545,10 @@ fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) {
         }
     }
 
-    if let ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::FnReturn(..), .. }) =
-        item.kind
+    if let ItemKind::OpaqueTy(hir::OpaqueTy {
+        origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
+        ..
+    }) = item.kind
     {
         let mut visitor = ProhibitOpaqueVisitor {
             opaque_identity_ty: tcx.mk_opaque(
@@ -563,13 +570,20 @@ fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) {
 
         if let Some(ty) = prohibit_opaque.break_value() {
             visitor.visit_item(&item);
+            let is_async = match item.kind {
+                ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => {
+                    matches!(origin, hir::OpaqueTyOrigin::AsyncFn(..))
+                }
+                _ => unreachable!(),
+            };
 
             let mut err = struct_span_err!(
                 tcx.sess,
                 span,
                 E0760,
-                "`impl Trait` return type cannot contain a projection or `Self` that references lifetimes from \
+                "`{}` return type cannot contain a projection or `Self` that references lifetimes from \
                  a parent scope",
+                if is_async { "async fn" } else { "impl Trait" },
             );
 
             for (span, name) in visitor.selftys {