mirror of
https://github.com/golang/go
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51 lines
735 B
Go
51 lines
735 B
Go
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// run
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// Copyright 2022 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package main
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func returnOption[T any](n int) Option[T] {
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if n == 1 {
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return Some[T]{}
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} else {
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return None{}
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}
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}
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type Option[T any] interface {
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sealedOption()
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}
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type Some[T any] struct {
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val T
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}
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func (s Some[T]) Value() T {
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return s.val
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}
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func (s Some[T]) sealedOption() {}
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type None struct{}
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func (s None) sealedOption() {}
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func main() {
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s := returnOption[int](1)
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_ = s.(Some[int])
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s = returnOption[int](0)
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_ = s.(None)
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switch (any)(s).(type) {
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case Some[int]:
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panic("s is a Some[int]")
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case None:
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// ok
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default:
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panic("oops")
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}
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}
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