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