error: implementation of `Foo` is not general enough --> $DIR/issue-46989.rs:38:5 | LL | assert_foo::(); | ^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Foo` is not general enough | = note: `Foo` would have to be implemented for the type `for<'a> fn(&'a i32)` = note: ...but `Foo` is actually implemented for the type `fn(&'0 i32)`, for some specific lifetime `'0` error: aborting due to previous error