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37 lines
672 B
Rust
37 lines
672 B
Rust
#![deny(deref_into_dyn_supertrait)]
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#![feature(trait_upcasting)] // remove this and the test compiles
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use std::ops::Deref;
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trait Bar<T> {}
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impl<T, U> Bar<U> for T {}
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trait Foo: Bar<i32> {
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fn as_dyn_bar_u32<'a>(&self) -> &(dyn Bar<u32> + 'a);
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}
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impl Foo for () {
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fn as_dyn_bar_u32<'a>(&self) -> &(dyn Bar<u32> + 'a) {
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self
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}
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}
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impl<'a> Deref for dyn Foo + 'a {
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type Target = dyn Bar<u32> + 'a;
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fn deref(&self) -> &Self::Target {
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self.as_dyn_bar_u32()
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}
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}
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fn take_dyn<T>(x: &dyn Bar<T>) -> T {
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todo!()
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}
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fn main() {
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let x: &dyn Foo = &();
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let y = take_dyn(x);
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let z: u32 = y;
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//~^ ERROR mismatched types
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}
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