src/test/ui/traits/issue-38604.rs

   1 trait Q<T:?Sized> {}
   2 trait Foo where u32: Q<Self> {
   3     fn foo(&self);
   4 }
   5
   6 impl Q<()> for u32 {}
   7 impl Foo for () {
   8     fn foo(&self) {
   9         println!("foo!");
  10     }
  11 }
  12
  13 fn main() {
  14     let _f: Box<dyn Foo> = //~ ERROR `Foo` cannot be made into an object
  15         Box::new(()); //~ ERROR `Foo` cannot be made into an object
  16 }