src/test/ui/nll/closure-requirements/propagate-approximated-fail-no-postdom.rs

   1 // Test where we fail to approximate due to demanding a postdom
   2 // relationship between our upper bounds.
   3
   4 // compile-flags:-Zverbose
   5
   6 #![feature(rustc_attrs)]
   7
   8 use std::cell::Cell;
   9
  10 // Callee knows that:
  11 //
  12 // 'x: 'a
  13 // 'x: 'b
  14 // 'c: 'y
  15 //
  16 // we have to prove that `'x: 'y`. We currently can only approximate
  17 // via a postdominator -- hence we fail to choose between `'a` and
  18 // `'b` here and report the error in the closure.
  19 fn establish_relationships<'a, 'b, 'c, F>(
  20     _cell_a: Cell<&'a u32>,
  21     _cell_b: Cell<&'b u32>,
  22     _cell_c: Cell<&'c u32>,
  23     _closure: F,
  24 ) where
  25     F: for<'x, 'y> FnMut(
  26         Cell<&'a &'x u32>, // shows that 'x: 'a
  27         Cell<&'b &'x u32>, // shows that 'x: 'b
  28         Cell<&'y &'c u32>, // shows that 'c: 'y
  29         Cell<&'x u32>,
  30         Cell<&'y u32>,
  31     ),
  32 {
  33 }
  34
  35 fn demand_y<'x, 'y>(_cell_x: Cell<&'x u32>, _cell_y: Cell<&'y u32>, _y: &'y u32) {}
  36
  37 #[rustc_regions]
  38 fn supply<'a, 'b, 'c>(cell_a: Cell<&'a u32>, cell_b: Cell<&'b u32>, cell_c: Cell<&'c u32>) {
  39     establish_relationships(
  40         cell_a,
  41         cell_b,
  42         cell_c,
  43         |_outlives1, _outlives2, _outlives3, x, y| {
  44             // Only works if 'x: 'y:
  45             let p = x.get();
  46             demand_y(x, y, p) //~ ERROR
  47         },
  48     );
  49 }
  50
  51 fn main() {}