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Rollup merge of #117959 - estebank:issue-76086, r=compiler-errors

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Better handle type errors involving `Self` literals

When encountering a type error involving a `Self` literal, point at the self type of the enclosing `impl` and suggest using the actual type name instead.

```
error[E0308]: mismatched types
  --> $DIR/struct-path-self-type-mismatch.rs:13:9
   |
LL |   impl<T> Foo<T> {
   |        -  ------ this is the type of the `Self` literal
   |        |
   |        found type parameter
LL |       fn new<U>(u: U) -> Foo<U> {
   |              -           ------ expected `Foo<U>` because of return type
   |              |
   |              expected type parameter
LL | /         Self {
LL | |
LL | |             inner: u
LL | |
LL | |         }
   | |_________^ expected `Foo<U>`, found `Foo<T>`
   |
   = note: expected struct `Foo<U>`
              found struct `Foo<T>`
   = note: a type parameter was expected, but a different one was found; you might be missing a type parameter or trait bound
   = note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters
help: use the type name directly
   |
LL |         Foo::<U> {
   |         ~~~~~~~~
```
Fix #76086.
This commit is contained in:
Matthias Krüger 2023-11-17 00:41:23 +01:00 committed by GitHub
commit dd49c39e02
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2 changed files with 61 additions and 1 deletions
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54
compiler/rustc_hir_typeck/src/demand.rs
View File

@ -31,6 +31,7 @@ pub fn emit_type_mismatch_suggestions(
}
self.annotate_alternative_method_deref(err, expr, error);
self.explain_self_literal(err, expr, expected, expr_ty);
// Use `||` to give these suggestions a precedence
let suggested = self.suggest_missing_parentheses(err, expr)
@ -1027,6 +1028,59 @@ pub(crate) fn is_destruct_assignment_desugaring(&self, expr: &hir::Expr<'_>) ->
return false;
}
fn explain_self_literal(
&self,
err: &mut Diagnostic,
expr: &hir::Expr<'tcx>,
expected: Ty<'tcx>,
found: Ty<'tcx>,
) {
match expr.peel_drop_temps().kind {
hir::ExprKind::Struct(
hir::QPath::Resolved(
None,
hir::Path { res: hir::def::Res::SelfTyAlias { alias_to, .. }, span, .. },
),
..,
)
| hir::ExprKind::Call(
hir::Expr {
kind:
hir::ExprKind::Path(hir::QPath::Resolved(
None,
hir::Path {
res: hir::def::Res::SelfTyAlias { alias_to, .. },
span,
..
},
)),
..
},
..,
) => {
if let Some(hir::Node::Item(hir::Item {
kind: hir::ItemKind::Impl(hir::Impl { self_ty, .. }),
..
})) = self.tcx.hir().get_if_local(*alias_to)
{
err.span_label(self_ty.span, "this is the type of the `Self` literal");
}
if let ty::Adt(e_def, e_args) = expected.kind()
&& let ty::Adt(f_def, _f_args) = found.kind()
&& e_def == f_def
{
err.span_suggestion_verbose(
*span,
"use the type name directly",
self.tcx.value_path_str_with_args(*alias_to, e_args),
Applicability::MaybeIncorrect,
);
}
}
_ => {}
}
}
fn note_wrong_return_ty_due_to_generic_arg(
&self,
err: &mut Diagnostic,

8
tests/ui/structs/struct-path-self-type-mismatch.stderr
View File

@ -24,7 +24,9 @@ error[E0308]: mismatched types
--> $DIR/struct-path-self-type-mismatch.rs:13:9
|
LL | impl<T> Foo<T> {
| - found type parameter
| - ------ this is the type of the `Self` literal
| |
| found type parameter
LL | fn new<U>(u: U) -> Foo<U> {
| - ------ expected `Foo<U>` because of return type
| |
@ -40,6 +42,10 @@ LL | | }
found struct `Foo<T>`
= note: a type parameter was expected, but a different one was found; you might be missing a type parameter or trait bound
= note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters
help: use the type name directly
|
LL | Foo::<U> {
| ~~~~~~~~
error: aborting due to 3 previous errors