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Delegation: support generics for delegation from free functions (The PR was split from https://github.com/rust-lang/rust/pull/123958, explainer - https://github.com/Bryanskiy/posts/blob/master/delegation%20in%20generic%20contexts.md) This PR implements generics inheritance from free functions to free functions and trait methods. #### free functions to free functions: ```rust fn to_reuse<T: Clone>(_: T) {} reuse to_reuse as bar; // desugaring: fn bar<T: Clone>(x: T) { to_reuse(x) } ``` Generics, predicates and signature are simply copied. Generic arguments in paths are ignored during generics inheritance: ```rust fn to_reuse<T: Clone>(_: T) {} reuse to_reuse::<u8> as bar; // desugaring: fn bar<T: Clone>(x: T) { to_reuse::<u8>(x) // ERROR: mismatched types } ``` Due to implementation limitations callee path is lowered without modifications. Therefore, it is a compilation error at the moment. #### free functions to trait methods: ```rust trait Trait<'a, A> { fn foo<'b, B>(&self, x: A, y: B) {...} } reuse Trait::foo; // desugaring: fn foo<'a, 'b, This: Trait<'a, A>, A, B>(this: &This, x: A, y: B) { Trait::foo(this, x, y) } ``` The inheritance is similar to the previous case but with some corrections: - `Self` parameter converted into `T: Trait` - generic parameters need to be reordered so that lifetimes go first Arguments are similarly ignored. --- In the future, we plan to support generic inheritance for delegating from all contexts to all contexts (from free/trait/impl to free/trait /impl). These cases were considered first as the simplest from the implementation perspective. |
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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.