rust/compiler/rustc_ast_lowering
bors 7402519c63 Auto merge of #109010 - compiler-errors:rtn, r=eholk
Initial support for return type notation (RTN)

See: https://smallcultfollowing.com/babysteps/blog/2023/02/13/return-type-notation-send-bounds-part-2/

1. Only supports `T: Trait<method(): Send>` style bounds, not `<T as Trait>::method(): Send`. Checking validity and injecting an implicit binder for all of the late-bound method generics is harder to do for the latter.
    * I'd add this in a follow-up.
3. ~Doesn't support RTN in general type position, i.e. no `let x: <T as Trait>::method() = ...`~
    * I don't think we actually want this.
5. Doesn't add syntax for "eliding" the function args -- i.e. for now, we write `method(): Send` instead of `method(..): Send`.
    * May be a hazard if we try to add it in the future. I'll probably add it in a follow-up later, with a structured suggestion to change `method()` to `method(..)` once we add it.
7. ~I'm not in love with the feature gate name 😺~
    * I renamed it to `return_type_notation` ✔️

Follow-up PRs will probably add support for `where T::method(): Send` bounds. I'm not sure if we ever want to support return-type-notation in arbitrary type positions. I may also make the bounds require `..` in the args list later.

r? `@ghost`
2023-03-31 18:04:12 +00:00
..
src Auto merge of #109010 - compiler-errors:rtn, r=eholk 2023-03-31 18:04:12 +00:00
Cargo.toml Upgrade thin-vec from 0.2.9 to 0.2.12. 2023-02-21 11:51:55 +11:00
messages.ftl Add (..) syntax for RTN 2023-03-28 01:14:28 +00:00