rust/tests/ui/traits/trivial_impl_sized.rs

//! This test checks that we currently need to implement
//! members, even if their where bounds don't hold for the impl type.

trait Foo {
    fn foo()
    where
        Self: Sized;
}

impl Foo for () {
    fn foo() {}
}

// Must not be allowed
impl Foo for i32 {}
//~^ ERROR: not all trait items implemented, missing: `foo`

// Should be allowed
impl Foo for dyn std::fmt::Debug {}
//~^ ERROR: not all trait items implemented, missing: `foo`

impl Foo for dyn std::fmt::Display {
    fn foo() {}
}

fn main() {}