bors f967532a47 Auto merge of #118420 - compiler-errors:async-gen, r=eholk ... Introduce support for `async gen` blocks I'm delighted to demonstrate that `async gen` block are not very difficult to support. They're simply coroutines that yield `Poll<Option<T>>` and return `()`. **This PR is WIP and in draft mode for now** -- I'm mostly putting it up to show folks that it's possible. This PR needs a lang-team experiment associated with it or possible an RFC, since I don't think it falls under the jurisdiction of the `gen` RFC that was recently authored by oli (https://github.com/rust-lang/rfcs/pull/3513, https://github.com/rust-lang/rust/issues/117078). ### Technical note on the pre-generator-transform yield type: The reason that the underlying coroutines yield `Poll<Option<T>>` and not `Poll<T>` (which would make more sense, IMO, for the pre-transformed coroutine), is because the `TransformVisitor` that is used to turn coroutines into built-in state machine functions would have to destructure and reconstruct the latter into the former, which requires at least inserting a new basic block (for a `switchInt` terminator, to match on the `Poll` discriminant). This does mean that the desugaring (at the `rustc_ast_lowering` level) of `async gen` blocks is a bit more involved. However, since we already need to intercept both `.await` and `yield` operators, I don't consider it much of a technical burden. r? `@ghost`		2023-12-08 19:13:57 +00:00
..
src	Auto merge of #118420 - compiler-errors:async-gen, r=eholk	2023-12-08 19:13:57 +00:00
Cargo.toml	Clean up rustc_*/Cargo.toml.	2023-10-30 08:46:02 +11:00
messages.ftl	Keep fluent slugs in alphabetical order	2023-10-05 16:17:32 +02:00