20af878588
Robustify and genericize return-type-notation resolution in `resolve_bound_vars` #129629 implemented return-type-notation (RTN) in its path form, like `where T::method(..): Bound`. As part of lowering, we must record the late-bound vars for the where clause introduced by the method (namely, its early- and late-bound lifetime arguments, since `where T::method(..)` turns into a higher-ranked where clause over all of the lifetimes according to [RFC 3654](https://rust-lang.github.io/rfcs/3654-return-type-notation.html#converting-to-higher-ranked-trait-bounds)). However, this logic was only looking at the where clauses of the parent item that the `T::method(..)` bound was written on, and not any parent items. This PR generalizes that logic to look at the parent item (i.e. the outer impl or trait) instead and fixes a (debug only) assertion as an effect. This logic is also more general and likely easier to adapt to more interesting (though likely very far off) cases like non-lifetime binder `for<T: Trait> T::method(..): Send` bounds. Tracking: - https://github.com/rust-lang/rust/issues/109417 |
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| README.md | ||
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.