// Regression test for #19618.
// Generic interface inference should bind nested generic struct arguments.

interface MyInterface[T] {
    is_good(a T) bool
}

struct MyStruct[T] {}

struct Opt[T] {
    x ?T
}

fn (_ MyStruct[T]) is_good(a Opt[T]) bool {
    if _ := a.x {
        return true
    }
    return false
}

fn check[T](a MyInterface[T], b T) bool {
    return a.is_good(b)
}

fn test_generic_interface_infers_nested_generic_struct_argument() {
    a := MyStruct[int]{}
    b := Opt[int]{
        x: 6
    }
    assert check(a, b)
}