f967532a47
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` |
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| .. | ||
| arena.rs | ||
| def_path_hash_map.rs | ||
| def.rs | ||
| definitions.rs | ||
| diagnostic_items.rs | ||
| hir_id.rs | ||
| hir.rs | ||
| intravisit.rs | ||
| lang_items.rs | ||
| lib.rs | ||
| pat_util.rs | ||
| stable_hash_impls.rs | ||
| target.rs | ||
| tests.rs | ||
| weak_lang_items.rs | ||