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Rollup of 5 pull requests - #71046
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Dylan-DPC-zz wants to merge 18 commits into
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… r=Centril
Handle `impl Trait` where `Trait` has an assoc type with missing bounds
When encountering a type parameter that needs more bounds the trivial case is `T` `where T: Bound`, but it can also be an `impl Trait` param that needs to be decomposed to a type param for cleaner code. For example, given
```rust
fn foo(constraints: impl Iterator) {
for constraint in constraints {
println!("{:?}", constraint);
}
}
```
the previous output was
```
error[E0277]: `<impl Iterator as std::iter::Iterator>::Item` doesn't implement `std::fmt::Debug`
--> src/main.rs:3:26
|
1 | fn foo(constraints: impl Iterator) {
| - help: consider further restricting the associated type: `where <impl Iterator as std::iter::Iterator>::Item: std::fmt::Debug`
2 | for constraint in constraints {
3 | println!("{:?}", constraint);
| ^^^^^^^^^^ `<impl Iterator as std::iter::Iterator>::Item` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
|
= help: the trait `std::fmt::Debug` is not implemented for `<impl Iterator as std::iter::Iterator>::Item`
= note: required by `std::fmt::Debug::fmt`
```
which is incorrect as `where <impl Iterator as std::iter::Iterator>::Item: std::fmt::Debug` is not valid syntax nor would it restrict the positional `impl Iterator` parameter if it were.
The output being introduced is
```
error[E0277]: `<impl Iterator as std::iter::Iterator>::Item` doesn't implement `std::fmt::Debug`
--> src/main.rs:3:26
|
3 | println!("{:?}", constraint);
| ^^^^^^^^^^ `<impl Iterator as std::iter::Iterator>::Item` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
|
= help: the trait `std::fmt::Debug` is not implemented for `<impl Iterator as std::iter::Iterator>::Item`
= note: required by `std::fmt::Debug::fmt`
help: introduce a type parameter with a trait bound instead of using `impl Trait`
|
LL | fn foo<T: Iterator>(constraints: T) where <T as std::iter::Iterator>::Item: std::fmt::Debug {
| ^^^^^^^^^^^^^ ^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```
This suggestion is correct and lead the user in the right direction: because you have an associated type restriction you can no longer use `impl Trait`, the only reasonable alternative is to introduce a named type parameter, bound by `Trait` and with a `where` binding on the associated type for the new type parameter `as Trait` for the missing bound.
*Ideally*, we would want to suggest something like the following, but that is not valid syntax today
```
error[E0277]: `<impl Iterator as std::iter::Iterator>::Item` doesn't implement `std::fmt::Debug`
--> src/main.rs:3:26
|
3 | println!("{:?}", constraint);
| ^^^^^^^^^^ `<impl Iterator as std::iter::Iterator>::Item` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
|
= help: the trait `std::fmt::Debug` is not implemented for `<impl Iterator as std::iter::Iterator>::Item`
= note: required by `std::fmt::Debug::fmt`
help: introduce a type parameter with a trait bound instead of using `impl Trait`
|
LL | fn foo(constraints: impl Iterator<Item: std::fmt::Debug>) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```
Fixrust-lang#69638.…=eddyb Pass the `PlaceElem::Index` local to `visit_local` Fixesrust-lang#71008 cc @rust-lang/wg-mir-opt r? @spastorino
…p, r=Amanieu [windows] Add testscase for self-contained executables
…an-DPC Clean up E0515 explanation r? @Dylan-DPC
…schievink Update links of `rustc guide` Picks up the things we left behind in the transition, hopefully they're last ones. r? @spastorino
Dylan-DPC-zz
commented
Apr 12, 2020
Author
@bors r+ p=5 rollup=never |
bors
commented
Apr 12, 2020
Collaborator
📌 Commit 082db80 has been approved by |
bors
commented
Apr 12, 2020
Collaborator
⌛ Testing commit 082db80 with merge 4006305ff68920a709ca1a671a69552264f16931... |
bors
commented
Apr 12, 2020
Collaborator
💔 Test failed - checks-azure |
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Successful merges:
impl TraitwhereTraithas an assoc type with missing bounds #69707 (Handleimpl TraitwhereTraithas an assoc type with missing bounds)PlaceElem::Indexlocal tovisit_local#71013 (Pass thePlaceElem::Indexlocal tovisit_local)rustc guide#71041 (Update links ofrustc guide)Failed merges:
r? @ghost