mirror of
https://github.com/golang/go
synced 2024-11-26 17:07:09 -07:00
51 lines
735 B
Go
51 lines
735 B
Go
|
// run
|
||
|
|
|
||
|
|
// Copyright 2022 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 main
|
||
|
|
|
||
|
|
func returnOption[T any](n int) Option[T] {
|
||
|
|
if n == 1 {
|
||
|
|
return Some[T]{}
|
||
|
|
} else {
|
||
|
|
return None{}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
type Option[T any] interface {
|
||
|
|
sealedOption()
|
||
|
|
}
|
||
|
|
|
||
|
|
type Some[T any] struct {
|
||
|
|
val T
|
||
|
|
}
|
||
|
|
|
||
|
|
func (s Some[T]) Value() T {
|
||
|
|
return s.val
|
||
|
|
}
|
||
|
|
|
||
|
|
func (s Some[T]) sealedOption() {}
|
||
|
|
|
||
|
|
type None struct{}
|
||
|
|
|
||
|
|
func (s None) sealedOption() {}
|
||
|
|
|
||
|
|
func main() {
|
||
|
|
s := returnOption[int](1)
|
||
|
|
_ = s.(Some[int])
|
||
|
|
|
||
|
|
s = returnOption[int](0)
|
||
|
|
_ = s.(None)
|
||
|
|
|
||
|
|
switch (any)(s).(type) {
|
||
|
|
case Some[int]:
|
||
|
|
panic("s is a Some[int]")
|
||
|
|
case None:
|
||
|
|
// ok
|
||
|
|
default:
|
||
|
|
panic("oops")
|
||
|
|
}
|
||
|
|
}
|