mirror of https://github.com/rust-lang/rust
37 lines
840 B
Rust
37 lines
840 B
Rust
#![feature(specialization)] //~ WARN the feature `specialization` is incomplete
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// Make sure we can't project defaulted associated types
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trait Foo {
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type Assoc;
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}
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impl<T> Foo for T {
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default type Assoc = ();
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}
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impl Foo for u8 {
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type Assoc = String;
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}
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fn generic<T>() -> <T as Foo>::Assoc {
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// `T` could be some downstream crate type that specializes (or,
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// for that matter, `u8`).
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() //~ ERROR mismatched types
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}
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fn monomorphic() -> () {
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// Even though we know that `()` is not specialized in a
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// downstream crate, typeck refuses to project here.
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generic::<()>() //~ ERROR mismatched types
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}
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fn main() {
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// No error here, we CAN project from `u8`, as there is no `default`
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// in that impl.
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let s: String = generic::<u8>();
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println!("{}", s); // bad news if this all compiles
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}
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