32 lines
522 B
Rust
32 lines
522 B
Rust
|
// check-pass
|
||
|
|
|
||
|
|
trait Variable<'a> {
|
||
|
|
type Type;
|
||
|
|
}
|
||
|
|
|
||
|
|
impl Variable<'_> for () {
|
||
|
|
type Type = ();
|
||
|
|
}
|
||
|
|
|
||
|
|
fn check<F, T>(_: F)
|
||
|
|
where
|
||
|
|
F: Fn(T), // <- if removed, all fn_* then require type annotations
|
||
|
|
F: for<'a> Fn(<T as Variable<'a>>::Type),
|
||
|
|
T: for<'a> Variable<'a>,
|
||
|
|
{
|
||
|
|
}
|
||
|
|
|
||
|
|
fn test(arg: impl Fn(())) {
|
||
|
|
fn fn_1(_: ()) {}
|
||
|
|
let fn_2 = |_: ()| ();
|
||
|
|
let fn_3 = |a| fn_1(a);
|
||
|
|
let fn_4 = arg;
|
||
|
|
|
||
|
|
check(fn_1); // Error
|
||
|
|
check(fn_2); // Ok
|
||
|
|
check(fn_3); // Ok
|
||
|
|
check(fn_4); // Error
|
||
|
|
}
|
||
|
|
|
||
|
|
fn main() {}
|