src/test/ui/regions/regions-variance-contravariant-use-contravariant.rs

   1 // run-pass
   2 #![allow(dead_code)]
   3 #![allow(unused_variables)]
   4 // Test that a type which is contravariant with respect to its region
   5 // parameter compiles successfully when used in a contravariant way.
   6 //
   7 // Note: see ui/variance/variance-regions-*.rs for the tests that check that the
   8 // variance inference works in the first place.
   9
  10 // pretty-expanded FIXME #23616
  11
  12 struct Contravariant<'a> {
  13     f: &'a isize
  14 }
  15
  16 fn use_<'a>(c: Contravariant<'a>) {
  17     let x = 3;
  18
  19     // 'b winds up being inferred to this call.
  20     // Contravariant<'a> <: Contravariant<'call> is true
  21     // if 'call <= 'a, which is true, so no error.
  22     collapse(&x, c);
  23
  24     fn collapse<'b>(x: &'b isize, c: Contravariant<'b>) { }
  25 }
  26
  27 pub fn main() {}