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// Similarly to escape-argument-callee, a test case where the closure
// requires a relationship between 2 unrelated higher-ranked regions,
// with no helpful relations between the HRRs and free regions.
//
// In this case, the error is reported by the closure itself. This is
// because it is unable to approximate the higher-ranked region `'x`,
// as it only knows of regions that `'x` is outlived by, and none that
// `'x` outlives.
// compile-flags:-Zverbose
#![feature(rustc_attrs)]
use std::cell::Cell;
// Callee knows that:
//
// 'a: 'x
// 'b: 'y
//
// but this doesn't really help us in proving that `'x: 'y`, so
// closure gets an error. In particular, we would need to know that
// `'x: 'a`, so that we could approximate `'x` "downwards" to `'a`.
fn establish_relationships<'a, 'b, F>(_cell_a: &Cell<&'a u32>, _cell_b: &Cell<&'b u32>, _closure: F)
where
F: for<'x, 'y> FnMut(
&Cell<&'x &'a u32>, // shows that 'a: 'x
&Cell<&'y &'b u32>, // shows that 'b: 'y
&Cell<&'x u32>,
&Cell<&'y u32>,
),
{
}
fn demand_y<'x, 'y>(_cell_x: &Cell<&'x u32>, _cell_y: &Cell<&'y u32>, _y: &'y u32) {}
#[rustc_regions]
fn supply<'a, 'b>(cell_a: Cell<&'a u32>, cell_b: Cell<&'b u32>) {
establish_relationships(&cell_a, &cell_b, |_outlives1, _outlives2, x, y| {
// Only works if 'x: 'y:
demand_y(x, y, x.get())
//~^ ERROR
});
}
fn main() {}
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