1 #![feature(type_alias_impl_trait)]
3 type Foo = impl std::fmt::Debug;
5 fn foo(b: bool) -> Foo {
9 let mut x = foo(false);
10 x = std::iter::empty().collect(); //~ ERROR `Foo` cannot be built from an iterator
14 fn bar(b: bool) -> impl std::fmt::Debug {
18 let mut x = bar(false);
19 x = std::iter::empty().collect(); //~ ERROR `impl Debug` cannot be built from an iterator