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rperierrperier
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Add a note when a type implements a trait with the same name as the required one
This is useful when you have two dependencies that use different trait for the same thing and with the same name. The user can accidentally implement the bad one which might be confusing.
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‎compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs‎

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@@ -498,6 +498,8 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
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);
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}
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self.suggest_impl_similarly_named_trait(&mut err, &obligation, leaf_trait_predicate);
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self.try_to_add_help_message(
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&root_obligation,
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&obligation,

‎compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs‎

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Original file line numberDiff line numberDiff line change
@@ -5127,6 +5127,73 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
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_ => {}
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}
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}
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pub(crate) fn suggest_impl_similarly_named_trait(
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&self,
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err: &mut Diag<'_>,
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obligation: &PredicateObligation<'tcx>,
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trait_predicate: ty::PolyTraitPredicate<'tcx>,
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) {
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let trait_def_id = trait_predicate.def_id();
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let trait_name = self.tcx.item_name(trait_def_id);
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let trait_has_same_params = |other_trait_def_id: DefId| -> bool {
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let trait_generics = self.tcx.generics_of(trait_def_id);
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let other_trait_generics = self.tcx.generics_of(other_trait_def_id);
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if trait_generics.count() != other_trait_generics.count() {
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return false;
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}
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trait_generics.own_params.iter().zip(other_trait_generics.own_params.iter()).all(
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|(a, b)| {
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a.name == b.name
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&& a.index == b.index
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&& ((matches!(a.kind, ty::GenericParamDefKind::Type { .. })
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&& matches!(b.kind, ty::GenericParamDefKind::Type { .. }))
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|| (matches!(a.kind, ty::GenericParamDefKind::Lifetime,)
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&& matches!(b.kind, ty::GenericParamDefKind::Lifetime))
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|| (matches!(a.kind, ty::GenericParamDefKind::Const { .. })
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&& matches!(b.kind, ty::GenericParamDefKind::Const { .. })))
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},
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)
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};
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if let Some(other_trait_def_id) = self.tcx.all_traits_including_private().find(|def_id| {
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trait_def_id != *def_id
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&& trait_name == self.tcx.item_name(def_id)
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&& trait_has_same_params(*def_id)
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&& self
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.tcx
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.predicates_of(*def_id)
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.instantiate(self.tcx, trait_predicate.skip_binder().trait_ref.args)
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.predicates
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.iter()
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.find(|clause| {
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if clause
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.as_trait_clause()
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.map_or(false, |trait_clause| trait_clause.def_id() == *def_id)
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== false
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{
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return false;
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}
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let pred = clause.as_trait_clause().unwrap();
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self.predicate_must_hold_modulo_regions(&Obligation::new(
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self.tcx,
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obligation.cause.clone(),
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obligation.param_env,
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pred,
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))
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})
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.is_some()
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}) {
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err.note(format!(
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"`{}` implements similarly named `{}`, but not `{}`",
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trait_predicate.self_ty(),
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self.tcx.def_path_str(other_trait_def_id),
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trait_predicate.print_modifiers_and_trait_path()
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));
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}
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()
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}
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}
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/// Add a hint to add a missing borrow or remove an unnecessary one.

‎tests/run-make/crate-loading-crate-depends-on-itself/foo.stderr‎

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@@ -4,6 +4,7 @@ error[E0277]: the trait bound `foo::Struct: Trait` is not satisfied
44
13 | check_trait::<foo::Struct>();
55
| ^^^^^^^^^^^ the trait `Trait` is not implemented for `foo::Struct`
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|
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= note: `foo::Struct` implements similarly named `foo::Trait`, but not `Trait`
78
note: there are multiple different versions of crate `foo` in the dependency graph
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--> foo-current.rs:7:1
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|

‎tests/run-make/crate-loading/multiple-dep-versions.stderr‎

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@@ -6,6 +6,7 @@ LL | do_something(Type);
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| |
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| required by a bound introduced by this call
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|
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= note: `dep_2_reexport::Type` implements similarly named `dependency::Trait`, but not `Trait`
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note: there are multiple different versions of crate `dependency` in the dependency graph
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--> replaced
1112
|
@@ -92,6 +93,7 @@ LL | do_something(OtherType);
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| |
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| required by a bound introduced by this call
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|
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= note: `OtherType` implements similarly named `dependency::Trait`, but not `Trait`
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note: there are multiple different versions of crate `dependency` in the dependency graph
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--> replaced
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|

‎tests/ui/traits/bound/same-crate-name.stderr‎

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@@ -12,6 +12,7 @@ help: trait impl with same name found
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LL | impl Bar for Foo {}
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| ^^^^^^^^^^^^^^^^
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= note: perhaps two different versions of crate `crate_a2` are being used?
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= note: `Foo` implements similarly named `main::a::Bar`, but not `main::a::Bar`
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= help: the trait `main::a::Bar` is implemented for `ImplementsTraitForUsize<usize>`
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note: required by a bound in `try_foo`
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--> $DIR/auxiliary/crate_a1.rs:3:24
@@ -48,6 +49,7 @@ help: trait impl with same name found
4849
LL | impl Bar for ImplementsWrongTraitConditionally<isize> {}
4950
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
5051
= note: perhaps two different versions of crate `crate_a2` are being used?
52+
= note: `ImplementsWrongTraitConditionally<isize>` implements similarly named `main::a::Bar`, but not `main::a::Bar`
5153
= help: the trait `main::a::Bar` is implemented for `ImplementsTraitForUsize<usize>`
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note: required by a bound in `try_foo`
5355
--> $DIR/auxiliary/crate_a1.rs:3:24

‎tests/ui/traits/similarly_named_trait.rs‎

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@@ -0,0 +1,27 @@
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trait Trait {} //~ HELP this trait has no implementations, consider adding one
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trait TraitWithParam<T> {} //~ HELP this trait has no implementations, consider adding one
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4+
mod m {
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pub trait Trait {}
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pub trait TraitWithParam<T> {}
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pub struct St;
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impl Trait for St {}
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impl<T> TraitWithParam<T> for St {}
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}
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fn func<T: Trait>(_: T) {} //~ NOTE required by a bound in `func`
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//~^ NOTE required by this bound in `func`
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fn func2<T: TraitWithParam<T>> (_: T) {} //~ NOTE required by a bound in `func2`
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//~^ NOTE required by this bound in `func2`
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18+
fn main() {
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func(m::St); //~ ERROR the trait bound `St: Trait` is not satisfied
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//~^ NOTE the trait `Trait` is not implemented for `St`
21+
//~| NOTE required by a bound introduced by this call
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//~| NOTE `St` implements similarly named `m::Trait`, but not `Trait`
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func2(m::St); //~ ERROR the trait bound `St: TraitWithParam<St>` is not satisfied
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//~^ NOTE the trait `TraitWithParam<St>` is not implemented for `St`
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//~| NOTE required by a bound introduced by this call
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//~| NOTE `St` implements similarly named `m::TraitWithParam`, but not `TraitWithParam<St>`
27+
}

‎tests/ui/traits/similarly_named_trait.stderr‎

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@@ -0,0 +1,43 @@
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error[E0277]: the trait bound `St: Trait` is not satisfied
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--> $DIR/similarly_named_trait.rs:19:10
3+
|
4+
LL | func(m::St);
5+
| ---- ^^^^^ the trait `Trait` is not implemented for `St`
6+
| |
7+
| required by a bound introduced by this call
8+
|
9+
= note: `St` implements similarly named `m::Trait`, but not `Trait`
10+
help: this trait has no implementations, consider adding one
11+
--> $DIR/similarly_named_trait.rs:1:1
12+
|
13+
LL | trait Trait {}
14+
| ^^^^^^^^^^^
15+
note: required by a bound in `func`
16+
--> $DIR/similarly_named_trait.rs:12:12
17+
|
18+
LL | fn func<T: Trait>(_: T) {}
19+
| ^^^^^ required by this bound in `func`
20+
21+
error[E0277]: the trait bound `St: TraitWithParam<St>` is not satisfied
22+
--> $DIR/similarly_named_trait.rs:23:11
23+
|
24+
LL | func2(m::St);
25+
| ----- ^^^^^ the trait `TraitWithParam<St>` is not implemented for `St`
26+
| |
27+
| required by a bound introduced by this call
28+
|
29+
= note: `St` implements similarly named `m::TraitWithParam`, but not `TraitWithParam<St>`
30+
help: this trait has no implementations, consider adding one
31+
--> $DIR/similarly_named_trait.rs:2:1
32+
|
33+
LL | trait TraitWithParam<T> {}
34+
| ^^^^^^^^^^^^^^^^^^^^^^^
35+
note: required by a bound in `func2`
36+
--> $DIR/similarly_named_trait.rs:15:13
37+
|
38+
LL | fn func2<T: TraitWithParam<T>> (_: T) {}
39+
| ^^^^^^^^^^^^^^^^^ required by this bound in `func2`
40+
41+
error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0277`.

‎tests/ui/union/issue-81199.stderr‎

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@@ -16,6 +16,7 @@ error[E0277]: the trait bound `T: Pointee` is not satisfied
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LL | components: PtrComponents<T>,
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| ^^^^^^^^^^^^^^^^ the trait `Pointee` is not implemented for `T`
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|
19+
= note: `T` implements similarly named `std::ptr::Pointee`, but not `Pointee`
1920
note: required by a bound in `PtrComponents`
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--> $DIR/issue-81199.rs:11:25
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|

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