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Extend support of _ in type parameters

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- Account for `impl Trait<_>`.
 - Provide a reasonable `Span` for empty `Generics` in `impl`s.
 - Account for `fn foo<_>(_: _) {}` to suggest `fn foo<T>(_: T) {}`.
 - Fix #67995.
This commit is contained in:
Esteban Küber 2020-01-09 13:46:37 -08:00
parent ed6468da16
commit c751961d29
6 changed files with 91 additions and 12 deletions
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13
src/test/ui/typeck/typeck_type_placeholder_item.rs
View file

@ -131,3 +131,16 @@ trait T {
fn assoc_fn_test3() -> _;
//~^ ERROR the type placeholder `_` is not allowed within types on item signatures
}
struct BadStruct<_>(_);
//~^ ERROR expected identifier, found reserved identifier `_`
//~| ERROR the type placeholder `_` is not allowed within types on item signatures
trait BadTrait<_> {}
//~^ ERROR expected identifier, found reserved identifier `_`
impl BadTrait<_> for BadStruct<_> {}
//~^ ERROR the type placeholder `_` is not allowed within types on item signatures
fn impl_trait() -> impl BadTrait<_> {
//~^ ERROR the type placeholder `_` is not allowed within types on item signatures
unimplemented!()
}

44
src/test/ui/typeck/typeck_type_placeholder_item.stderr
View file

@ -1,3 +1,15 @@
error: expected identifier, found reserved identifier `_`
--> $DIR/typeck_type_placeholder_item.rs:135:18
|
LL | struct BadStruct<_>(_);
| ^ expected identifier, found reserved identifier
error: expected identifier, found reserved identifier `_`
--> $DIR/typeck_type_placeholder_item.rs:138:16
|
LL | trait BadTrait<_> {}
| ^ expected identifier, found reserved identifier
error[E0121]: the type placeholder `_` is not allowed within types on item signatures
--> $DIR/typeck_type_placeholder_item.rs:4:14
|
@ -255,6 +267,36 @@ LL | fn fn_test13(x: _) -> (i32, _) { (x, x) }
| | not allowed in type signatures
| help: replace with the correct return type: `(i32, i32)`
error[E0121]: the type placeholder `_` is not allowed within types on item signatures
--> $DIR/typeck_type_placeholder_item.rs:135:21
|
LL | struct BadStruct<_>(_);
| ^ not allowed in type signatures
|
help: use type parameters instead
|
LL | struct BadStruct<T>(T);
| ^ ^
error[E0121]: the type placeholder `_` is not allowed within types on item signatures
--> $DIR/typeck_type_placeholder_item.rs:140:15
|
LL | impl BadTrait<_> for BadStruct<_> {}
| ^ ^ not allowed in type signatures
| |
| not allowed in type signatures
|
help: use type parameters instead
|
LL | impl<T> BadTrait<T> for BadStruct<T> {}
| ^^^ ^ ^
error[E0121]: the type placeholder `_` is not allowed within types on item signatures
--> $DIR/typeck_type_placeholder_item.rs:143:34
|
LL | fn impl_trait() -> impl BadTrait<_> {
| ^ not allowed in type signatures
error[E0121]: the type placeholder `_` is not allowed within types on item signatures
--> $DIR/typeck_type_placeholder_item.rs:121:31
|
@ -405,7 +447,7 @@ help: use type parameters instead
LL | fn clone_from<T>(&mut self, other: T) { *self = FnTest9; }
| ^^^ ^
error: aborting due to 40 previous errors
error: aborting due to 45 previous errors
Some errors have detailed explanations: E0121, E0282.
For more information about an error, try `rustc --explain E0121`.