golang issue39754 代码
文件路径：/src/go/types/testdata/fixedbugs/issue39754.go
/ 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]]
}