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Fix implicit Sized relaxation when attempting to relax other, unsupported trait

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This commit is contained in:
robojumper 2021-07-18 12:29:21 +02:00
parent 4156473bca
commit 3dbe0cebd8
3 changed files with 17 additions and 25 deletions
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1
compiler/rustc_typeck/src/astconv/mod.rs
View File

@ -838,6 +838,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
this does nothing because the given bound is not \
a default; only `?Sized` is supported",
);
return false;
}
}
}

3
src/test/ui/issues/issue-87199.rs
View File

@ -7,15 +7,14 @@
// Check that these function definitions only emit warnings, not errors
fn arg<T: ?Send>(_: T) {}
//~^ warning: default bound relaxed for a type parameter, but this does nothing
//~^^ the size for values of type `T`
fn ref_arg<T: ?Send>(_: &T) {}
//~^ warning: default bound relaxed for a type parameter, but this does nothing
fn ret() -> impl Iterator<Item = ()> + ?Send { std::iter::empty() }
//~^ warning: default bound relaxed for a type parameter, but this does nothing
//~^^ the size for values of type `impl Iterator+?Sized` cannot be known
// Check that there's no `?Sized` relaxation!
fn main() {
ref_arg::<i32>(&5);
ref_arg::<[i32]>(&[5]);
//~^ the size for values of type `[i32]` cannot be known
}

38
src/test/ui/issues/issue-87199.stderr
View File

@ -5,40 +5,32 @@ LL | fn arg<T: ?Send>(_: T) {}
| ^
warning: default bound relaxed for a type parameter, but this does nothing because the given bound is not a default; only `?Sized` is supported
--> $DIR/issue-87199.rs:11:12
--> $DIR/issue-87199.rs:10:12
|
LL | fn ref_arg<T: ?Send>(_: &T) {}
| ^
warning: default bound relaxed for a type parameter, but this does nothing because the given bound is not a default; only `?Sized` is supported
--> $DIR/issue-87199.rs:13:13
--> $DIR/issue-87199.rs:12:13
|
LL | fn ret() -> impl Iterator<Item = ()> + ?Send { std::iter::empty() }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error[E0277]: the size for values of type `impl Iterator+?Sized` cannot be known at compilation time
--> $DIR/issue-87199.rs:13:13
error[E0277]: the size for values of type `[i32]` cannot be known at compilation time
--> $DIR/issue-87199.rs:18:22
|
LL | fn ret() -> impl Iterator<Item = ()> + ?Send { std::iter::empty() }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
LL | fn ref_arg<T: ?Send>(_: &T) {}
| - required by this bound in `ref_arg`
...
LL | ref_arg::<[i32]>(&[5]);
| ^^^^ doesn't have a size known at compile-time
|
= help: the trait `Sized` is not implemented for `impl Iterator+?Sized`
= note: the return type of a function must have a statically known size
= help: the trait `Sized` is not implemented for `[i32]`
help: consider relaxing the implicit `Sized` restriction
|
LL | fn ref_arg<T: ?Send + ?Sized>(_: &T) {}
| ^^^^^^^^
error[E0277]: the size for values of type `T` cannot be known at compilation time
--> $DIR/issue-87199.rs:8:18
|
LL | fn arg<T: ?Send>(_: T) {}
| - ^ doesn't have a size known at compile-time
| |
| this type parameter needs to be `std::marker::Sized`
|
= help: unsized fn params are gated as an unstable feature
help: function arguments must have a statically known size, borrowed types always have a known size
|
LL | fn arg<T: ?Send>(_: &T) {}
| ^
error: aborting due to 2 previous errors; 3 warnings emitted
error: aborting due to previous error; 3 warnings emitted
For more information about this error, try `rustc --explain E0277`.