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Extraneous comma in trait bound suggestion #72693
Description
The following code (Playground):
trait T1 {
type A;
}
trait T2: T1
where
Self::A: Clone,
{
}
fn generic<T: T2>()
where
u8: Copy,
{
}Produces an invalid suggestion:
error[E0277]: the trait bound `<T as T1>::A: std::clone::Clone` is not satisfied
--> src/lib.rs:11:15
|
5 | trait T2: T1
| -- required by a bound in this
6 | where
7 | Self::A: Clone,
| ----- required by this bound in `T2`
...
11 | fn generic<T: T2>()
| ^^ the trait `std::clone::Clone` is not implemented for `<T as T1>::A`
|
help: consider further restricting the associated type
|
13 | u8: Copy,, <T as T1>::A: std::clone::Clone
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
on nightly. On stable, the error message looks a bit different but seems to also be suggesting an extra comma.
When trying to reduce this test case I found that in other cases this same lint seems to suggest the right thing (this may be useful as an additional test case):
#[derive(Clone)]
struct Generic<T>(T);
fn generic<T>() -> impl Clone
where
Generic<T>: Default,
{
Generic::<T>::default()
}correct suggestion (nightly):
Standard Error
Compiling playground v0.0.1 (/playground)
error[E0277]: the trait bound `T: std::clone::Clone` is not satisfied
--> src/lib.rs:4:20
|
4 | fn generic<T>() -> impl Clone
| ^^^^^^^^^^ the trait `std::clone::Clone` is not implemented for `T`
...
8 | Generic::<T>::default()
| ----------------------- this returned value is of type `Generic<T>`
|
= note: required because of the requirements on the impl of `std::clone::Clone` for `Generic<T>`
= note: the return type of a function must have a statically known size
help: consider further restricting type parameter `T`
|
6 | Generic<T>: Default, T: std::clone::Clone
| ^^^^^^^^^^^^^^^^^^^^^^
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Area: Messages for errors, warnings, and lintsArea: Suggestions generated by the compiler applied by `cargo fix`Category: This is a bug.Diagnostics: A diagnostic that is giving misleading or incorrect information.Diagnostics: An error or lint that needs small tweaks.Relevant to the compiler team, which will review and decide on the PR/issue.
Activity
Account for trailing comma when suggesting `where` clauses
Rollup merge of rust-lang#72715 - estebank:trailing-comma-where, r=pe…
Rollup merge of rust-lang#72715 - estebank:trailing-comma-where, r=pe…