TAIT fails where RPIT works #101903
Description
I tried this code:
trait Duh {} impl Duh for i32 {} trait Trait { type Assoc: Duh; } impl<R: Duh, F: FnMut() -> R> Trait for F { type Assoc = R; } type Sendable = impl Send; type Foo = impl Trait<Assoc = Sendable>; fn foo() -> Foo { || 42 }I expected to see this happen: it compiles, just like
trait Duh {} impl Duh for i32 {} trait Trait { type Assoc: Duh; } impl<R: Duh, F: FnMut() -> R> Trait for F { type Assoc = R; } type Sendable = impl Send; fn foo() -> impl Trait<Assoc = Sendable> { || 42 }Instead, this happened:
error[[E0277]](https://doc.rust-lang.org/nightly/error-index.html#E0277): the trait bound `Sendable: Duh` is not satisfied --> src/lib.rs:19:5 | 19 | || 42 | ^^^^^ the trait `Duh` is not implemented for `Sendable` | = help: the trait `Duh` is implemented for `i32` note: required for `[closure@src/lib.rs:19:5: 19:7]` to implement `Trait` --> src/lib.rs:10:31 | 10 | impl<R: Duh, F: FnMut() -> R> Trait for F { | ^^^^^ ^