// Copyright 2020 The Go Authors. All rights reserved. | |
// Use of this source code is governed by a BSD-style | |
// license that can be found in the LICENSE file. | |
package p | |
type Optional[T any] struct {} | |
func (_ Optional[T]) Val() (T, bool) | |
type Box[T any] interface { | |
Val() (T, bool) | |
} | |
func f[V interface{}, A, B Box[V]]() {} | |
func _() { | |
f[int, Optional[int], Optional[int]]() | |
_ = f[int, Optional[int], Optional /* ERROR does not implement Box */ [string]] | |
_ = f[int, Optional[int], Optional /* ERROR Optional.* does not implement Box.* */ [string]] | |
} |