src/test/ui/impl-trait/issues/issue-70877.rs

   1 #![feature(type_alias_impl_trait)]
   2
   3 type FooArg<'a> = &'a dyn ToString;
   4 type FooRet = impl std::fmt::Debug;
   5
   6 type FooItem = Box<dyn Fn(FooArg) -> FooRet>;
   7 type Foo = impl Iterator<Item = FooItem>;
   8
   9 #[repr(C)]
  10 struct Bar(u8);
  11
  12 impl Iterator for Bar {
  13     type Item = FooItem;
  14
  15     fn next(&mut self) -> Option<Self::Item> {
  16         Some(Box::new(quux))
  17     }
  18 }
  19
  20 fn quux(st: FooArg) -> FooRet {
  21     Some(st.to_string())
  22 }
  23
  24 fn ham() -> Foo {
  25     Bar(1)
  26 }
  27
  28 fn oof() -> impl std::fmt::Debug {
  29     let mut bar = ham();
  30     let func = bar.next().unwrap();
  31     return func(&"oof"); //~ ERROR opaque type's hidden type cannot be another opaque type
  32 }
  33
  34 fn main() {
  35     let _ = oof();
  36 }