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Auto merge of #66561 - TimoFreiberg:trait-name-report, r=estebank
Add version mismatch help message for unimplemented trait Improves issue #22750 The error reporting for E0277 (the trait `X` is not implemented for `Foo`) now checks whether `Foo` implements a trait with the same path as `X`, which probably means that the programmer wanted to actually use only one version of the trait `X` instead of the two. Still open: * the same diagnostic should be added for [the trait method case](#22750 (comment)) * Showing the real crate versions would be nice, but rustc currently doesn't have that information [according to Esteban](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/diagnostics.20for.20crate.20version.20mismatch/near/180572989)
2 parents 2626f3d + 2a0292f commit 0f6f66f

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‎src/librustc/traits/error_reporting.rs‎

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@@ -38,6 +38,7 @@ use std::fmt;
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use syntax::ast;
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use syntax::symbol::{sym, kw};
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use syntax_pos::{DUMMY_SP, Span, ExpnKind, MultiSpan};
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use rustc::hir::def_id::LOCAL_CRATE;
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use rustc_error_codes::*;
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@@ -799,6 +800,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
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self.suggest_fn_call(&obligation, &mut err, &trait_ref, points_at_arg);
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self.suggest_remove_reference(&obligation, &mut err, &trait_ref);
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self.suggest_semicolon_removal(&obligation, &mut err, span, &trait_ref);
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self.note_version_mismatch(&mut err, &trait_ref);
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// Try to report a help message
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if !trait_ref.has_infer_types() &&
@@ -1050,6 +1052,43 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
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err.emit();
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}
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/// If the `Self` type of the unsatisfied trait `trait_ref` implements a trait
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/// with the same path as `trait_ref`, a help message about
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/// a probable version mismatch is added to `err`
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fn note_version_mismatch(
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&self,
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err: &mut DiagnosticBuilder<'_>,
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trait_ref: &ty::PolyTraitRef<'tcx>,
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) {
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let get_trait_impl = |trait_def_id| {
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let mut trait_impl = None;
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self.tcx.for_each_relevant_impl(trait_def_id, trait_ref.self_ty(), |impl_def_id| {
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if trait_impl.is_none() {
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trait_impl = Some(impl_def_id);
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}
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});
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trait_impl
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};
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let required_trait_path = self.tcx.def_path_str(trait_ref.def_id());
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let all_traits = self.tcx.all_traits(LOCAL_CRATE);
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let traits_with_same_path: std::collections::BTreeSet<_> = all_traits
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.iter()
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.filter(|trait_def_id| **trait_def_id != trait_ref.def_id())
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.filter(|trait_def_id| self.tcx.def_path_str(**trait_def_id) == required_trait_path)
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.collect();
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for trait_with_same_path in traits_with_same_path {
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if let Some(impl_def_id) = get_trait_impl(*trait_with_same_path) {
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let impl_span = self.tcx.def_span(impl_def_id);
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err.span_help(impl_span, "trait impl with same name found");
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let trait_crate = self.tcx.crate_name(trait_with_same_path.krate);
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let crate_msg = format!(
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"Perhaps two different versions of crate `{}` are being used?",
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trait_crate
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);
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err.note(&crate_msg);
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}
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}
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}
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fn suggest_restricting_param_bound(
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&self,
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err: &mut DiagnosticBuilder<'_>,

‎src/test/ui/traits/auxiliary/crate_a1.rs‎

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@@ -1,11 +1,9 @@
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pub struct Foo;
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pub trait Bar {}
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pub trait Bar{}
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pub fn try_foo(x: impl Bar) {}
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pub fn bar() -> Box<Bar> {
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unimplemented!()
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pub struct ImplementsTraitForUsize<T> {
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_marker: std::marker::PhantomData<T>,
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}
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9-
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pub fn try_foo(x: Foo){}
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pub fn try_bar(x: Box<Bar>){}
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impl Bar for ImplementsTraitForUsize<usize> {}

‎src/test/ui/traits/auxiliary/crate_a2.rs‎

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@@ -0,0 +1,13 @@
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pub struct Foo;
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pub trait Bar {}
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impl Bar for Foo {}
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pub struct DoesNotImplementTrait;
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pub struct ImplementsWrongTraitConditionally<T> {
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_marker: std::marker::PhantomData<T>,
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}
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impl Bar for ImplementsWrongTraitConditionally<isize> {}

‎src/test/ui/traits/trait-bounds-same-crate-name.rs‎

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@@ -0,0 +1,55 @@
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// aux-build:crate_a1.rs
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// aux-build:crate_a2.rs
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// Issue 22750
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// This tests the extra help message reported when a trait bound
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// is not met but the struct implements a trait with the same path.
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fn main() {
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let foo = {
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extern crate crate_a2 as a;
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a::Foo
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};
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let implements_no_traits = {
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extern crate crate_a2 as a;
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a::DoesNotImplementTrait
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};
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let other_variant_implements_mismatched_trait = {
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extern crate crate_a2 as a;
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a::ImplementsWrongTraitConditionally { _marker: std::marker::PhantomData::<isize> }
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};
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let other_variant_implements_correct_trait = {
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extern crate crate_a1 as a;
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a::ImplementsTraitForUsize { _marker: std::marker::PhantomData::<isize> }
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};
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{
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extern crate crate_a1 as a;
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a::try_foo(foo);
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//~^ ERROR E0277
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//~| trait impl with same name found
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//~| Perhaps two different versions of crate `crate_a2`
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// We don't want to see the "version mismatch" help message here
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// because `implements_no_traits` has no impl for `Foo`
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a::try_foo(implements_no_traits);
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//~^ ERROR E0277
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41+
// We don't want to see the "version mismatch" help message here
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// because `other_variant_implements_mismatched_trait`
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// does not have an impl for its `<isize>` variant,
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// only for its `<usize>` variant.
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a::try_foo(other_variant_implements_mismatched_trait);
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//~^ ERROR E0277
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48+
// We don't want to see the "version mismatch" help message here
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// because `ImplementsTraitForUsize` only has
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// impls for the correct trait where the path is not misleading.
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a::try_foo(other_variant_implements_correct_trait);
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//~^ ERROR E0277
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//~| the following implementations were found:
54+
}
55+
}

‎src/test/ui/traits/trait-bounds-same-crate-name.stderr‎

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@@ -0,0 +1,64 @@
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error[E0277]: the trait bound `main::a::Foo: main::a::Bar` is not satisfied
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--> $DIR/trait-bounds-same-crate-name.rs:31:20
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|
4+
LL | a::try_foo(foo);
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| ^^^ the trait `main::a::Bar` is not implemented for `main::a::Foo`
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|
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::: $DIR/auxiliary/crate_a1.rs:3:24
8+
|
9+
LL | pub fn try_foo(x: impl Bar) {}
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| --- required by this bound in `main::a::try_foo`
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|
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help: trait impl with same name found
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--> $DIR/auxiliary/crate_a2.rs:5:1
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|
15+
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?
18+
19+
error[E0277]: the trait bound `main::a::DoesNotImplementTrait: main::a::Bar` is not satisfied
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--> $DIR/trait-bounds-same-crate-name.rs:38:20
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|
22+
LL | a::try_foo(implements_no_traits);
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| ^^^^^^^^^^^^^^^^^^^^ the trait `main::a::Bar` is not implemented for `main::a::DoesNotImplementTrait`
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|
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::: $DIR/auxiliary/crate_a1.rs:3:24
26+
|
27+
LL | pub fn try_foo(x: impl Bar) {}
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| --- required by this bound in `main::a::try_foo`
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30+
error[E0277]: the trait bound `main::a::ImplementsWrongTraitConditionally<isize>: main::a::Bar` is not satisfied
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--> $DIR/trait-bounds-same-crate-name.rs:45:20
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|
33+
LL | a::try_foo(other_variant_implements_mismatched_trait);
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `main::a::Bar` is not implemented for `main::a::ImplementsWrongTraitConditionally<isize>`
35+
|
36+
::: $DIR/auxiliary/crate_a1.rs:3:24
37+
|
38+
LL | pub fn try_foo(x: impl Bar) {}
39+
| --- required by this bound in `main::a::try_foo`
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|
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help: trait impl with same name found
42+
--> $DIR/auxiliary/crate_a2.rs:13:1
43+
|
44+
LL | impl Bar for ImplementsWrongTraitConditionally<isize> {}
45+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
46+
= note: Perhaps two different versions of crate `crate_a2` are being used?
47+
48+
error[E0277]: the trait bound `main::a::ImplementsTraitForUsize<isize>: main::a::Bar` is not satisfied
49+
--> $DIR/trait-bounds-same-crate-name.rs:51:20
50+
|
51+
LL | a::try_foo(other_variant_implements_correct_trait);
52+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `main::a::Bar` is not implemented for `main::a::ImplementsTraitForUsize<isize>`
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|
54+
::: $DIR/auxiliary/crate_a1.rs:3:24
55+
|
56+
LL | pub fn try_foo(x: impl Bar) {}
57+
| --- required by this bound in `main::a::try_foo`
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|
59+
= help: the following implementations were found:
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<main::a::ImplementsTraitForUsize<usize> as main::a::Bar>
61+
62+
error: aborting due to 4 previous errors
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For more information about this error, try `rustc --explain E0277`.

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