rust/tests/mir-opt/building/async_await.rs
Arpad Borsos 96931a787a
Transform async ResumeTy in generator transform
- Eliminates all the `get_context` calls that async lowering created.
- Replace all `Local` `ResumeTy` types with `&mut Context<'_>`.

The `Local`s that have their types replaced are:
- The `resume` argument itself.
- The argument to `get_context`.
- The yielded value of a `yield`.

The `ResumeTy` hides a `&mut Context<'_>` behind an unsafe raw pointer, and the
`get_context` function is being used to convert that back to a `&mut Context<'_>`.

Ideally the async lowering would not use the `ResumeTy`/`get_context` indirection,
but rather directly use `&mut Context<'_>`, however that would currently
lead to higher-kinded lifetime errors.
See <https://github.com/rust-lang/rust/issues/105501>.

The async lowering step and the type / lifetime inference / checking are
still using the `ResumeTy` indirection for the time being, and that indirection
is removed here. After this transform, the generator body only knows about `&mut Context<'_>`.
2023-01-19 09:03:05 +01:00

18 lines
493 B
Rust

// This test makes sure that the generator MIR pass eliminates all calls to
// `get_context`, and that the MIR argument type for an async fn and all locals
// related to `yield` are `&mut Context`, and its return type is `Poll`.
// edition:2018
// compile-flags: -C panic=abort
#![crate_type = "lib"]
// EMIT_MIR async_await.a-{closure#0}.generator_resume.0.mir
async fn a() {}
// EMIT_MIR async_await.b-{closure#0}.generator_resume.0.mir
pub async fn b() {
a().await;
a().await
}