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// 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();
}
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