1 // Issue 52985: user code provides no use case that allows a type alias `impl Trait`
2 // We now emit a 'unconstrained opaque type' error
4 #![feature(type_alias_impl_trait)]
7 pub type Foo = impl Copy;
8 //~^ ERROR unconstrained opaque type
10 // make compiler happy about using 'Foo'
11 pub fn bar(x: Foo) -> Foo {
17 let _: foo::Foo = std::mem::transmute(0u8);