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// Test where we might in theory be able to see that the relationship
// between two bound regions is true within closure and hence have no
// need to propagate; but in fact we do because identity of free
// regions is erased.
// compile-flags:-Zverbose
// check-pass
#![feature(rustc_attrs)]
use std::cell::Cell;
// In theory, callee knows that:
//
// 'x: 'a
// 'a: 'y
//
// and hence could satisfy that `'x: 'y` locally. However, in our
// checking, we ignore the precise free regions that come into the
// region and just assign each position a distinct universally bound
// region. Hence, we propagate a constraint to our caller that will
// wind up being solvable.
fn establish_relationships<'a, F>(
_cell_a: Cell<&'a u32>,
_closure: F,
) where
F: for<'x, 'y> FnMut(
Cell<&'a &'x u32>, // shows that 'x: 'a
Cell<&'y &'a u32>, // shows that 'a: '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>(cell_a: Cell<&'a u32>) {
establish_relationships(
cell_a,
|_outlives1, _outlives2, x, y| {
// Only works if 'x: 'y:
let p = x.get();
demand_y(x, y, p)
},
);
}
fn main() {}
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