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33 lines
857 B
Rust
33 lines
857 B
Rust
#![feature(generic_const_exprs)]
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#![allow(incomplete_features)]
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use std::marker::PhantomData;
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trait SadBee {
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const ASSOC: usize;
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}
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// `fn(&'static ())` is a supertype of `for<'a> fn(&'a ())` while
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// we allow two different impls for these types, leading
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// to different const eval results.
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impl SadBee for for<'a> fn(&'a ()) {
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const ASSOC: usize = 0;
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}
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impl SadBee for fn(&'static ()) {
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//~^ WARN conflicting implementations of trait
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//~| WARN the behavior may change in a future release
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const ASSOC: usize = 100;
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}
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struct Foo<T: SadBee>([u8; <T as SadBee>::ASSOC], PhantomData<T>)
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where
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[(); <T as SadBee>::ASSOC]:;
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fn covariant(v: &'static Foo<for<'a> fn(&'a ())>) -> &'static Foo<fn(&'static ())> {
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v
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//~^ ERROR mismatched types
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}
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fn main() {
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let y = covariant(&Foo([], PhantomData));
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println!("{:?}", y.0);
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}
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