| //@ compile-flags: -Znext-solver |
| //@ check-pass |
| |
| fn map<T: Default, U, F: FnOnce(T) -> U>(f: F) { |
| f(T::default()); |
| } |
| |
| fn main() { |
| map::<i32, _ /* ?U */, _ /* ?F */>(|x| x.to_string()); |
| // PREVIOUSLY when confirming the `map` call, we register: |
| // |
| // (1.) ?F: FnOnce<(i32,)> |
| // (2.) <?F as FnOnce<(i32,)>>::Output projects-to ?U |
| // |
| // While (1.) is ambiguous, (2.) immediately gets processed |
| // and we infer `?U := <?F as FnOnce<(i32,)>>::Output`. |
| // |
| // Thus, the only pending obligation that remains is (1.). |
| // Since it is a trait obligation, we don't use it to deduce |
| // the closure signature, and we fail! |
| } |
