Improve ManuallyDrop suggestion

6 files changed, 42 insertions, 43 deletions

diff --git a/compiler/rustc_typeck/src/check/check.rs b/compiler/rustc_typeck/src/check/check.rs
index f0a77cb39a6..335814f8627 100644
--- a/compiler/rustc_typeck/src/check/check.rs
+++ b/compiler/rustc_typeck/src/check/check.rs
@@ -371,8 +371,13 @@ fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: LocalDefId) -> b
         let param_env = tcx.param_env(item_def_id);
         for field in fields {
             let field_ty = field.ty(tcx, substs);
-            // We are currently checking the type this field came from, so it must be local.
-            let field_span = tcx.hir().span_if_local(field.did).unwrap();
+            let (field_span, ty_span) =
+                // We are currently checking the type this field came from, so it must be local.
+                if let Node::Field(field) = tcx.hir().get_if_local(field.did).unwrap() {
+                    (field.span, field.ty.span)
+                } else {
+                    unreachable!("mir field has to correspond to hir field");
+                };
             if field_ty.needs_drop(tcx, param_env) {
                 struct_span_err!(
                     tcx.sess,
@@ -380,7 +385,11 @@ fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: LocalDefId) -> b
                     E0740,
                     "unions may not contain fields that need dropping"
                 )
-                .span_note(field_span, "`std::mem::ManuallyDrop` can be used to wrap the type")
+                .multipart_suggestion_verbose(
+                    "wrap the type with `std::mem::ManuallyDrop` and ensure it is manually dropped",
+                    vec![(ty_span, format!("std::mem::ManuallyDrop<{}>", field_ty))],
+                    Applicability::MaybeIncorrect,
+                )
                 .emit();
                 return false;
             }
diff --git a/src/test/ui/feature-gates/feature-gate-untagged_unions.stderr b/src/test/ui/feature-gates/feature-gate-untagged_unions.stderr
index ed973871b3f..a9ccb835587 100644
--- a/src/test/ui/feature-gates/feature-gate-untagged_unions.stderr
+++ b/src/test/ui/feature-gates/feature-gate-untagged_unions.stderr
@@ -13,11 +13,10 @@ error[E0740]: unions may not contain fields that need dropping
 LL |     a: String,
    |     ^^^^^^^^^
    |
-note: `std::mem::ManuallyDrop` can be used to wrap the type
-  --> $DIR/feature-gate-untagged_unions.rs:16:5
+help: wrap the type with `std::mem::ManuallyDrop` and ensure it is manually dropped
    |
-LL |     a: String,
-   |     ^^^^^^^^^
+LL |     a: std::mem::ManuallyDrop<String>,
+   |        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 error[E0740]: unions may not contain fields that need dropping
   --> $DIR/feature-gate-untagged_unions.rs:24:5
@@ -25,11 +24,10 @@ error[E0740]: unions may not contain fields that need dropping
 LL |     a: T,
    |     ^^^^
    |
-note: `std::mem::ManuallyDrop` can be used to wrap the type
-  --> $DIR/feature-gate-untagged_unions.rs:24:5
+help: wrap the type with `std::mem::ManuallyDrop` and ensure it is manually dropped
    |
-LL |     a: T,
-   |     ^^^^
+LL |     a: std::mem::ManuallyDrop<T>,
+   |        ~~~~~~~~~~~~~~~~~~~~~~~~~
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/union/issue-41073.stderr b/src/test/ui/union/issue-41073.stderr
index 2e9598b2271..04b4286cc4b 100644
--- a/src/test/ui/union/issue-41073.stderr
+++ b/src/test/ui/union/issue-41073.stderr
@@ -4,11 +4,10 @@ error[E0740]: unions may not contain fields that need dropping
 LL |     a: A,
    |     ^^^^
    |
-note: `std::mem::ManuallyDrop` can be used to wrap the type
-  --> $DIR/issue-41073.rs:4:5
+help: wrap the type with `std::mem::ManuallyDrop` and ensure it is manually dropped
    |
-LL |     a: A,
-   |     ^^^^
+LL |     a: std::mem::ManuallyDrop<A>,
+   |        ~~~~~~~~~~~~~~~~~~~~~~~~~
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/union/union-custom-drop.stderr b/src/test/ui/union/union-custom-drop.stderr
index ee2333f905f..0c59048f7fe 100644
--- a/src/test/ui/union/union-custom-drop.stderr
+++ b/src/test/ui/union/union-custom-drop.stderr
@@ -4,11 +4,10 @@ error[E0740]: unions may not contain fields that need dropping
 LL |     bar: Bar,
    |     ^^^^^^^^
    |
-note: `std::mem::ManuallyDrop` can be used to wrap the type
-  --> $DIR/union-custom-drop.rs:7:5
+help: wrap the type with `std::mem::ManuallyDrop` and ensure it is manually dropped
    |
-LL |     bar: Bar,
-   |     ^^^^^^^^
+LL |     bar: std::mem::ManuallyDrop<Bar>,
+   |          ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/union/union-with-drop-fields.mirunsafeck.stderr b/src/test/ui/union/union-with-drop-fields.mirunsafeck.stderr
index 2062fb7473f..8f3d30cd7ee 100644
--- a/src/test/ui/union/union-with-drop-fields.mirunsafeck.stderr
+++ b/src/test/ui/union/union-with-drop-fields.mirunsafeck.stderr
@@ -4,11 +4,10 @@ error[E0740]: unions may not contain fields that need dropping
 LL |     a: String,
    |     ^^^^^^^^^
    |
-note: `std::mem::ManuallyDrop` can be used to wrap the type
-  --> $DIR/union-with-drop-fields.rs:11:5
+help: wrap the type with `std::mem::ManuallyDrop` and ensure it is manually dropped
    |
-LL |     a: String,
-   |     ^^^^^^^^^
+LL |     a: std::mem::ManuallyDrop<String>,
+   |        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 error[E0740]: unions may not contain fields that need dropping
   --> $DIR/union-with-drop-fields.rs:19:5
@@ -16,11 +15,10 @@ error[E0740]: unions may not contain fields that need dropping
 LL |     a: S,
    |     ^^^^
    |
-note: `std::mem::ManuallyDrop` can be used to wrap the type
-  --> $DIR/union-with-drop-fields.rs:19:5
+help: wrap the type with `std::mem::ManuallyDrop` and ensure it is manually dropped
    |
-LL |     a: S,
-   |     ^^^^
+LL |     a: std::mem::ManuallyDrop<S>,
+   |        ~~~~~~~~~~~~~~~~~~~~~~~~~
 
 error[E0740]: unions may not contain fields that need dropping
   --> $DIR/union-with-drop-fields.rs:24:5
@@ -28,11 +26,10 @@ error[E0740]: unions may not contain fields that need dropping
 LL |     a: T,
    |     ^^^^
    |
-note: `std::mem::ManuallyDrop` can be used to wrap the type
-  --> $DIR/union-with-drop-fields.rs:24:5
+help: wrap the type with `std::mem::ManuallyDrop` and ensure it is manually dropped
    |
-LL |     a: T,
-   |     ^^^^
+LL |     a: std::mem::ManuallyDrop<T>,
+   |        ~~~~~~~~~~~~~~~~~~~~~~~~~
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/union/union-with-drop-fields.thirunsafeck.stderr b/src/test/ui/union/union-with-drop-fields.thirunsafeck.stderr
index 2062fb7473f..8f3d30cd7ee 100644
--- a/src/test/ui/union/union-with-drop-fields.thirunsafeck.stderr
+++ b/src/test/ui/union/union-with-drop-fields.thirunsafeck.stderr
@@ -4,11 +4,10 @@ error[E0740]: unions may not contain fields that need dropping
 LL |     a: String,
    |     ^^^^^^^^^
    |
-note: `std::mem::ManuallyDrop` can be used to wrap the type
-  --> $DIR/union-with-drop-fields.rs:11:5
+help: wrap the type with `std::mem::ManuallyDrop` and ensure it is manually dropped
    |
-LL |     a: String,
-   |     ^^^^^^^^^
+LL |     a: std::mem::ManuallyDrop<String>,
+   |        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 error[E0740]: unions may not contain fields that need dropping
   --> $DIR/union-with-drop-fields.rs:19:5
@@ -16,11 +15,10 @@ error[E0740]: unions may not contain fields that need dropping
 LL |     a: S,
    |     ^^^^
    |
-note: `std::mem::ManuallyDrop` can be used to wrap the type
-  --> $DIR/union-with-drop-fields.rs:19:5
+help: wrap the type with `std::mem::ManuallyDrop` and ensure it is manually dropped
    |
-LL |     a: S,
-   |     ^^^^
+LL |     a: std::mem::ManuallyDrop<S>,
+   |        ~~~~~~~~~~~~~~~~~~~~~~~~~
 
 error[E0740]: unions may not contain fields that need dropping
   --> $DIR/union-with-drop-fields.rs:24:5
@@ -28,11 +26,10 @@ error[E0740]: unions may not contain fields that need dropping
 LL |     a: T,
    |     ^^^^
    |
-note: `std::mem::ManuallyDrop` can be used to wrap the type
-  --> $DIR/union-with-drop-fields.rs:24:5
+help: wrap the type with `std::mem::ManuallyDrop` and ensure it is manually dropped
    |
-LL |     a: T,
-   |     ^^^^
+LL |     a: std::mem::ManuallyDrop<T>,
+   |        ~~~~~~~~~~~~~~~~~~~~~~~~~
 
 error: aborting due to 3 previous errors