rust/compiler/rustc_ast_lowering
bors 3cfa4def7c Auto merge of #91403 - cjgillot:inherit-async, r=oli-obk
Inherit lifetimes for async fn instead of duplicating them.

The current desugaring of `async fn foo<'a>(&usize) -> &u8` is equivalent to
```rust
fn foo<'a, '0>(&'0 usize) -> foo<'static, 'static>::Opaque<'a, '0, '_>;
type foo<'_a, '_0>::Opaque<'a, '0, '1> = impl Future<Output = &'1 u8>;
```
following the RPIT model.

Duplicating all the inherited lifetime parameters and setting the inherited version to `'static` makes lowering more complex and causes issues like #61949. This PR removes the duplication of inherited lifetimes to directly use
```rust
fn foo<'a, '0>(&'0 usize) -> foo<'a, '0>::Opaque<'_>;
type foo<'a, '0>::Opaque<'1> = impl Future<Output = &'1 u8>;
```
following the TAIT model.

Fixes https://github.com/rust-lang/rust/issues/61949
2022-02-12 21:42:10 +00:00
..
src Auto merge of #91403 - cjgillot:inherit-async, r=oli-obk 2022-02-12 21:42:10 +00:00
Cargo.toml Forbid hashing HIR outside of indexing. 2021-10-09 18:38:28 +02:00