Crash when type of closure has superclass-bound existential containing a function type containing a type parameter

[slavapestov]

class C<T> {}

protocol P {}

protocol Q {
  associatedtype A
}

func foo<T: Q>(t: T) {
  let fn: (any P & C<(T.A) -> ()>) -> T = { x in t }
}

[AnthonyLatsis]

Simplified it a bit:

func foo<T>(t: T) {
  let fn: (any P & C<T>) -> T = { x in t }
}