diff options
Diffstat (limited to 'src/test/ui/type-alias-impl-trait/implied_bounds_from_types.rs')
-rw-r--r-- | src/test/ui/type-alias-impl-trait/implied_bounds_from_types.rs | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/src/test/ui/type-alias-impl-trait/implied_bounds_from_types.rs b/src/test/ui/type-alias-impl-trait/implied_bounds_from_types.rs new file mode 100644 index 000000000..8023cd24f --- /dev/null +++ b/src/test/ui/type-alias-impl-trait/implied_bounds_from_types.rs @@ -0,0 +1,51 @@ +#![feature(type_alias_impl_trait)] + +type WithLifetime<T> = impl Equals<SelfType = ()>; +fn _defining_use<T>() -> WithLifetime<T> {} + +trait Convert<'a> { + type Witness; + fn convert<'b, T: ?Sized>(_proof: &'b Self::Witness, x: &'a T) -> &'b T; +} + +impl<'a> Convert<'a> for () { + type Witness = WithLifetime<&'a ()>; + + fn convert<'b, T: ?Sized>(_proof: &'b WithLifetime<&'a ()>, x: &'a T) -> &'b T { + // compiler used to think it gets to assume 'a: 'b here because + // of the `&'b WithLifetime<&'a ()>` argument + x + //~^ ERROR lifetime may not live long enough + } +} + +fn extend_lifetime<'a, 'b, T: ?Sized>(x: &'a T) -> &'b T { + WithLifetime::<&'a ()>::convert_helper::<(), T>(&(), x) +} + +trait Equals { + type SelfType; + fn convert_helper<'a, 'b, W: Convert<'a, Witness = Self>, T: ?Sized>( + proof: &'b Self::SelfType, + x: &'a T, + ) -> &'b T; +} + +impl<S> Equals for S { + type SelfType = Self; + fn convert_helper<'a, 'b, W: Convert<'a, Witness = Self>, T: ?Sized>( + proof: &'b Self, + x: &'a T, + ) -> &'b T { + W::convert(proof, x) + } +} + +fn main() { + let r; + { + let x = String::from("Hello World?"); + r = extend_lifetime(&x); + } + println!("{}", r); +} |