| // Test that the NLL `relate_tys` code correctly deduces that a |
| // function returning always its first argument can be upcast to one |
| // that returns either first or second argument. |
| |
| use std::cell::Cell; |
| |
| type DoubleCell<A> = Cell<(A, A)>; |
| type DoublePair<A> = (A, A); |
| |
| fn make_cell<'b>(x: &'b u32) -> Cell<(&'static u32, &'b u32)> { |
| panic!() |
| } |
| |
| fn main() { |
| let a: &'static u32 = &22; |
| let b = 44; |
| |
| // Here we get an error because `DoubleCell<_>` requires the same type |
| // on both parts of the `Cell`, and we can't have that. |
| let x: DoubleCell<_> = make_cell(&b); //~ ERROR |
| |
| // Here we do not get an error because `DoublePair<_>` permits |
| // variance on the lifetimes involved. |
| let y: DoublePair<_> = make_cell(&b).get(); |
| } |
