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