2 // ignore-compare-mode-nll
3 //[nll] compile-flags: -Z borrowck=mir
5 // Test an `exists<'a> { forall<'b> { 'a = 'b } }` pattern -- which should not compile!
7 // In particular, we test this pattern in trait solving, where it is not connected
8 // to any part of the source code.
16 T: Trait<for<'b> fn(Cell<&'b u32>)>,
20 impl<'a> Trait<fn(Cell<&'a u32>)> for () {}
23 // Here, proving that `(): Trait<for<'b> fn(&'b u32)>` uses the impl:
25 // - The impl provides the clause `forall<'a> { (): Trait<fn(&'a u32)> }`
26 // - We instantiate `'a` existentially to get `(): Trait<fn(&?a u32)>`
27 // - We unify `fn(&?a u32)` with `for<'b> fn(&'b u32)`
28 // - This requires (among other things) instantiating `'b` universally,
29 // yielding `fn(&!b u32)`, in a fresh universe U1
30 // - So we get `?a = !b` but the universe U0 assigned to `?a` cannot name `!b`.
32 foo::<()>(); //~ ERROR implementation of `Trait` is not general enough