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Merged
merged 1 commit into from
Sep 25, 2025
+14 −11
Merged

Improve derive suggestion of const param #146894

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11 changes: 7 additions & 4 deletions compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1305,17 +1305,20 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
{
if ty.is_structural_eq_shallow(self.tcx) {
diag.span_suggestion(
span,
"add `#[derive(ConstParamTy)]` to the struct",
span.shrink_to_lo(),
format!("add `#[derive(ConstParamTy)]` to the {}", def.descr()),
"#[derive(ConstParamTy)]\n",
Applicability::MachineApplicable,
);
} else {
// FIXME(adt_const_params): We should check there's not already an
// overlapping `Eq`/`PartialEq` impl.
diag.span_suggestion(
span,
"add `#[derive(ConstParamTy, PartialEq, Eq)]` to the struct",
span.shrink_to_lo(),
format!(
"add `#[derive(ConstParamTy, PartialEq, Eq)]` to the {}",
def.descr()
),
"#[derive(ConstParamTy, PartialEq, Eq)]\n",
Applicability::MachineApplicable,
);
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2 changes: 1 addition & 1 deletion tests/ui/const-generics/forbid-non-structural_match-types.stderr
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Expand Up @@ -6,8 +6,8 @@ LL | struct D<const X: C>;
|
help: add `#[derive(ConstParamTy, PartialEq, Eq)]` to the struct
|
LL - struct C;
LL + #[derive(ConstParamTy, PartialEq, Eq)]
LL | struct C;
|

error: aborting due to 1 previous error
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4 changes: 2 additions & 2 deletions tests/ui/const-generics/issue-80471.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -4,10 +4,10 @@ error[E0741]: `Nat` must implement `ConstParamTy` to be used as the type of a co
LL | fn foo<const N: Nat>() {}
| ^^^
|
help: add `#[derive(ConstParamTy)]` to the struct
help: add `#[derive(ConstParamTy)]` to the enum
|
LL - enum Nat {
LL + #[derive(ConstParamTy)]
LL | enum Nat {
|

error: aborting due to 1 previous error
Expand Down
4 changes: 2 additions & 2 deletions tests/ui/const-generics/issues/issue-97278.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -4,10 +4,10 @@ error[E0741]: `Bar` must implement `ConstParamTy` to be used as the type of a co
LL | fn test<const BAR: Bar>() {}
| ^^^
|
help: add `#[derive(ConstParamTy)]` to the struct
help: add `#[derive(ConstParamTy)]` to the enum
|
LL - enum Bar {
LL + #[derive(ConstParamTy)]
LL | enum Bar {
|

error: aborting due to 1 previous error
Expand Down
4 changes: 2 additions & 2 deletions tests/ui/consts/refs_check_const_eq-issue-88384.stderr
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Expand Up @@ -15,8 +15,8 @@ LL | struct Foo<const T: CompileTimeSettings>;
|
help: add `#[derive(ConstParamTy)]` to the struct
|
LL - struct CompileTimeSettings {
LL + #[derive(ConstParamTy)]
LL | struct CompileTimeSettings {
|

error[E0741]: `CompileTimeSettings` must implement `ConstParamTy` to be used as the type of a const generic parameter
Expand All @@ -27,8 +27,8 @@ LL | impl<const T: CompileTimeSettings> Foo<T> {
|
help: add `#[derive(ConstParamTy)]` to the struct
|
LL - struct CompileTimeSettings {
LL + #[derive(ConstParamTy)]
LL | struct CompileTimeSettings {
|

error: aborting due to 2 previous errors; 1 warning emitted
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