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Improve ManuallyDrop suggestion #90901

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Nov 17, 2021
Merged

Improve ManuallyDrop suggestion #90901

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Improve ManuallyDrop suggestion
rukai Nov 14, 2021
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rukai Nov 15, 2021
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15 changes: 12 additions & 3 deletions compiler/rustc_typeck/src/check/check.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -371,16 +371,25 @@ 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");
};
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Suggested change
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");
};
let (field_span, ty_span) = match tcx.hir().get_if_local(field.did) {
// We are currently checking the type this field came from, so it must be local.
Some(Node::Field(field)) => (field.span, field.ty.span),
_ => unreachable!("mir field has to correspond to hir field"),
};

if field_ty.needs_drop(tcx, param_env) {
struct_span_err!(
tcx.sess,
field_span,
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))],
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Suggested change
vec![(ty_span, format!("std::mem::ManuallyDrop<{}>", field_ty))],
vec![
(ty_span.shrink_to_lo(), "std::mem::ManuallyDrop<".to_string()),
(ty_span.shrink_to_hi(), ">".to_string()),
],

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oh thats clever!

Applicability::MaybeIncorrect,
)
.emit();
return false;
}
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14 changes: 6 additions & 8 deletions src/test/ui/feature-gates/feature-gate-untagged_unions.stderr
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Expand Up @@ -13,23 +13,21 @@ 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
|
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

Expand Down
7 changes: 3 additions & 4 deletions src/test/ui/union/issue-41073.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -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

Expand Down
7 changes: 3 additions & 4 deletions src/test/ui/union/union-custom-drop.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -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

Expand Down
21 changes: 9 additions & 12 deletions src/test/ui/union/union-with-drop-fields.mirunsafeck.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -4,35 +4,32 @@ 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
|
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
|
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

Expand Down
21 changes: 9 additions & 12 deletions src/test/ui/union/union-with-drop-fields.thirunsafeck.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -4,35 +4,32 @@ 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
|
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
|
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

Expand Down