src/test/ui/regions/regions-fn-subtyping.rs

   1 // run-pass
   2 #![allow(dead_code)]
   3 #![allow(unused_assignments)]
   4 // Issue #2263.
   5
   6 // pretty-expanded FIXME #23616
   7
   8 #![allow(unused_variables)]
   9
  10 // Should pass region checking.
  11 fn ok(f: Box<dyn FnMut(&usize)>) {
  12     // Here, g is a function that can accept a usize pointer with
  13     // lifetime r, and f is a function that can accept a usize pointer
  14     // with any lifetime.  The assignment g = f should be OK (i.e.,
  15     // f's type should be a subtype of g's type), because f can be
  16     // used in any context that expects g's type.  But this currently
  17     // fails.
  18     let mut g: Box<dyn for<'r> FnMut(&'r usize)> = Box::new(|x| { });
  19     g = f;
  20 }
  21
  22 // This version is the same as above, except that here, g's type is
  23 // inferred.
  24 fn ok_inferred(f: Box<dyn FnMut(&usize)>) {
  25     let mut g: Box<dyn for<'r> FnMut(&'r usize)> = Box::new(|_| {});
  26     g = f;
  27 }
  28
  29 pub fn main() {
  30 }