Rollup merge of #128527 - estebank:ambiguity-suggestion, r=Nadrieril

More information for fully-qualified suggestion when there are multiple impls ``` error[E0790]: cannot call associated function on trait without specifying the corresponding `impl` type --> $DIR/E0283.rs:30:21 | LL | fn create() -> u32; | ------------------- `Coroutine::create` defined here ... LL | let cont: u32 = Coroutine::create(); | ^^^^^^^^^^^^^^^^^^^ cannot call associated function of trait | help: use a fully-qualified path to a specific available implementation | LL | let cont: u32 = <Impl as Coroutine>::create(); | LL | let cont: u32 = <AnotherImpl as Coroutine>::create(); | ```
rust-lang · Aug 7, 2024 · 493233c · 493233c
2 parents a6cacee 2c83c99
commit 493233c
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diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
@@ -388,39 388,67 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
  trait_impls.non_blanket_impls().values().flatten().count();
  // If there is only one implementation of the trait, suggest using it.
  // Otherwise, use a placeholder comment for the implementation.
- let (message, self_type) = if non_blanket_impl_count == 1 {
  let (message, self_types) = if non_blanket_impl_count == 1 {
  (
  "use the fully-qualified path to the only available \
  implementation",
- format!(
  vec![format!(
  "{}",
  self.tcx.type_of(impl_def_id).instantiate_identity()
- ),
  )],
  )
  } else if non_blanket_impl_count < 20 {
  (
  "use a fully-qualified path to one of the available \
  implementations",
  trait_impls
  .non_blanket_impls()
  .values()
  .flatten()
  .map(|id| {
  format!(
  "{}",
  self.tcx.type_of(id).instantiate_identity()
  )
  })
  .collect::<Vec<String>>(),
  )
  } else {
  (
  "use a fully-qualified path to a specific available \
  implementation",
- "/* self type */".to_string(),
  vec!["/* self type */".to_string()],
  )
  };
- let mut suggestions =
- vec![(path.span.shrink_to_lo(), format!("<{self_type} as "))];
- if let Some(generic_arg) = trait_path_segment.args {
- let between_span =
- trait_path_segment.ident.span.between(generic_arg.span_ext);
- // get rid of :: between Trait and <type>
- // must be '::' between them, otherwise the parser won't accept the code
- suggestions.push((between_span, "".to_string()));
- suggestions
- .push((generic_arg.span_ext.shrink_to_hi(), ">".to_string()));
- } else {
- suggestions.push((
- trait_path_segment.ident.span.shrink_to_hi(),
- ">".to_string(),
- ));
- }
- err.multipart_suggestion(
  let suggestions: Vec<_> = self_types
  .into_iter()
  .map(|self_type| {
  let mut suggestions = vec![(
  path.span.shrink_to_lo(),
  format!("<{self_type} as "),
  )];
  if let Some(generic_arg) = trait_path_segment.args {
  let between_span = trait_path_segment
  .ident
  .span
  .between(generic_arg.span_ext);
  // get rid of :: between Trait and <type>
  // must be '::' between them, otherwise the parser won't accept the code
  suggestions.push((between_span, "".to_string()));
  suggestions.push((
  generic_arg.span_ext.shrink_to_hi(),
  ">".to_string(),
  ));
  } else {
  suggestions.push((
  trait_path_segment.ident.span.shrink_to_hi(),
  ">".to_string(),
  ));
  }
  suggestions
  })
  .collect();
  err.multipart_suggestions(
  message,
  suggestions,
  Applicability::MaybeIncorrect,

diff --git a/tests/ui/error-codes/E0283.stderr b/tests/ui/error-codes/E0283.stderr
@@ -7,10 7,12 @@ LL | fn create() -> u32;
 LL | let cont: u32 = Coroutine::create();
  | ^^^^^^^^^^^^^^^^^^^ cannot call associated function of trait
  |
-help: use a fully-qualified path to a specific available implementation
 help: use a fully-qualified path to one of the available implementations
  |
-LL | let cont: u32 = </* self type */ as Coroutine>::create();
- | 
 LL | let cont: u32 = <Impl as Coroutine>::create();
  | 
 LL | let cont: u32 = <AnotherImpl as Coroutine>::create();
  | 
 
 error[E0283]: type annotations needed
  --> $DIR/E0283.rs:35:24

diff --git a/tests/ui/error-codes/E0790.stderr b/tests/ui/error-codes/E0790.stderr
@@ -63,10 63,12 @@ LL | fn my_fn();
 LL | MyTrait2::my_fn();
  | ^^^^^^^^^^^^^^^^^ cannot call associated function of trait
  |
-help: use a fully-qualified path to a specific available implementation
 help: use a fully-qualified path to one of the available implementations
  |
-LL | </* self type */ as MyTrait2>::my_fn();
- | 
 LL | <Impl1 as MyTrait2>::my_fn();
  | 
 LL | <Impl2 as MyTrait2>::my_fn();
  | 
 
 error: aborting due to 5 previous errors