diff options
Diffstat (limited to 'src/test/ui/type-alias-impl-trait/issue-84660-unsoundness.rs')
-rw-r--r-- | src/test/ui/type-alias-impl-trait/issue-84660-unsoundness.rs | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/src/test/ui/type-alias-impl-trait/issue-84660-unsoundness.rs b/src/test/ui/type-alias-impl-trait/issue-84660-unsoundness.rs new file mode 100644 index 000000000..f12d1b6d9 --- /dev/null +++ b/src/test/ui/type-alias-impl-trait/issue-84660-unsoundness.rs @@ -0,0 +1,41 @@ +// Another example from issue #84660, this time weaponized as a safe transmute: an opaque type in an +// impl header being accepted was used to create unsoundness. + +#![feature(type_alias_impl_trait)] + +trait Foo {} +impl Foo for () {} +type Bar = impl Foo; +fn _defining_use() -> Bar {} + +trait Trait<T, In> { + type Out; + fn convert(i: In) -> Self::Out; +} + +impl<In, Out> Trait<Bar, In> for Out { //~ ERROR cannot implement trait + type Out = Out; + fn convert(_i: In) -> Self::Out { + unreachable!(); + } +} + +impl<In, Out> Trait<(), In> for Out { + type Out = In; + fn convert(i: In) -> Self::Out { + i + } +} + +fn transmute<In, Out>(i: In) -> Out { + <Out as Trait<Bar, In>>::convert(i) +} + +fn main() { + let d; + { + let x = "Hello World".to_string(); + d = transmute::<&String, &String>(&x); + } + println!("{}", d); +} |