/src/test/ui/traits/object/with-self-in-projection-output-repeated-supertrait.rs
https://gitlab.com/rust-lang/rust · Rust · 51 lines · 25 code · 9 blank · 17 comment · 3 complexity · 0502eea64083bbfcd6ba0a11a72e7adc MD5 · raw file
- // build-pass (FIXME(62277): could be check-pass?)
- // FIXME(eddyb) shorten the name so windows doesn't choke on it.
- #![crate_name = "trait_test"]
- // Regression test related to #56288. Check that a supertrait projection (of
- // `Output`) that references `Self` is ok if there is another occurrence of
- // the same supertrait that specifies the projection explicitly, even if
- // the projection's associated type is not explicitly specified in the object type.
- //
- // Note that in order for this to compile, we need the `Self`-referencing projection
- // to normalize fairly directly to a concrete type, otherwise the trait resolver
- // will hate us.
- //
- // There is a test in `trait-object-with-self-in-projection-output-bad.rs` that
- // having a normalizing, but `Self`-containing projection does not *by itself*
- // allow you to avoid writing the projected type (`Output`, in this example)
- // explicitly.
- trait ConstI32 {
- type Out;
- }
- impl<T: ?Sized> ConstI32 for T {
- type Out = i32;
- }
- trait Base {
- type Output;
- }
- trait NormalizingHelper: Base<Output=<Self as ConstI32>::Out> + Base<Output=i32> {
- type Target;
- }
- impl Base for u32
- {
- type Output = i32;
- }
- impl NormalizingHelper for u32
- {
- type Target = i32;
- }
- fn main() {
- // Make sure this works both with and without the associated type
- // being specified.
- let _x: Box<dyn NormalizingHelper<Target=i32>> = Box::new(2u32);
- let _y: Box<dyn NormalizingHelper<Target=i32, Output=i32>> = Box::new(2u32);
- }