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// 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")
}
}
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