src/test/ui/traits/object/with-self-in-projection-output-bad.rs

   1 // Regression test for #56288. Checks that if a supertrait defines an associated type
   2 // projection that references `Self`, then that associated type must still be explicitly
   3 // specified in the `dyn Trait` variant, since we don't know what `Self` is anymore.
   4
   5 trait Base {
   6     type Output;
   7 }
   8
   9 trait Helper: Base<Output=<Self as Helper>::Target> {
  10     type Target;
  11 }
  12
  13 impl Base for u32
  14 {
  15     type Output = i32;
  16 }
  17
  18 impl Helper for u32
  19 {
  20     type Target = i32;
  21 }
  22
  23 trait ConstI32 {
  24     type Out;
  25 }
  26
  27 impl<T: ?Sized> ConstI32 for T {
  28     type Out = i32;
  29 }
  30
  31 // Test that you still need to manually give a projection type if the Output type
  32 // is normalizable.
  33 trait NormalizableHelper:
  34     Base<Output=<Self as ConstI32>::Out>
  35 {
  36     type Target;
  37 }
  38
  39 impl NormalizableHelper for u32
  40 {
  41     type Target = i32;
  42 }
  43
  44 fn main() {
  45     let _x: Box<dyn Helper<Target=i32>> = Box::new(2u32);
  46     //~^ ERROR the value of the associated type `Output` (from trait `Base`) must be specified
  47
  48     let _y: Box<dyn NormalizableHelper<Target=i32>> = Box::new(2u32);
  49     //~^ ERROR the value of the associated type `Output` (from trait `Base`) must be specified
  50 }