src/test/ui/regions/regions-trait-object-subtyping.rs

   1 trait Dummy { fn dummy(&self); }
   2
   3 fn foo1<'a:'b,'b>(x: &'a mut (dyn Dummy+'a)) -> &'b mut (dyn Dummy+'b) {
   4     // Here, we are able to coerce
   5     x
   6 }
   7
   8 fn foo2<'a:'b,'b>(x: &'b mut (dyn Dummy+'a)) -> &'b mut (dyn Dummy+'b) {
   9     // Here, we are able to coerce
  10     x
  11 }
  12
  13 fn foo3<'a,'b>(x: &'a mut dyn Dummy) -> &'b mut dyn Dummy {
  14     // Without knowing 'a:'b, we can't coerce
  15     x //~ ERROR lifetime bound not satisfied
  16      //~^ ERROR cannot infer an appropriate lifetime
  17 }
  18
  19 struct Wrapper<T>(T);
  20 fn foo4<'a:'b,'b>(x: Wrapper<&'a mut dyn Dummy>) -> Wrapper<&'b mut dyn Dummy> {
  21     // We can't coerce because it is packed in `Wrapper`
  22     x //~ ERROR mismatched types
  23 }
  24
  25 fn main() {}