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https://github.com/golang/go
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e24977d231
The next CL will remove the -G flag, effectively hard-coding it to its current default (-G=3). Change-Id: Ib4743b529206928f9f1cca9fdb19989728327831 Reviewed-on: https://go-review.googlesource.com/c/go/+/388534 Reviewed-by: Keith Randall <khr@golang.org> Trust: Matthew Dempsky <mdempsky@google.com> Run-TryBot: Matthew Dempsky <mdempsky@google.com> TryBot-Result: Gopher Robot <gobot@golang.org>
68 lines
1.5 KiB
Go
68 lines
1.5 KiB
Go
// run
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// Copyright 2021 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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// Testing various generic uses of indexing, both for reads and writes.
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package main
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import "fmt"
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// Can index an argument (read/write) constrained to be a slice or an array.
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func Index1[T interface{ []int64 | [5]int64 }](x T) int64 {
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x[2] = 5
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return x[3]
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}
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// Can index an argument (read) constrained to be a byte array or a string.
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func Index2[T interface{ []byte | string }](x T) byte {
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return x[3]
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}
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// Can index an argument (write) constrained to be a byte array, but not a string.
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func Index2a[T interface{ []byte }](x T) byte {
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x[2] = 'b'
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return x[3]
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}
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// Can index an argument (read/write) constrained to be a map. Maps can't
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// be combined with any other type for indexing purposes.
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func Index3[T interface{ map[int]int64 }](x T) int64 {
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x[2] = 43
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return x[3]
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}
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// But the type of the map keys or values can be parameterized.
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func Index4[T any](x map[int]T) T {
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var zero T
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x[2] = zero
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return x[3]
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}
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func test[T comparable](got, want T) {
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if got != want {
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panic(fmt.Sprintf("got %v, want %v", got, want))
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}
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}
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func main() {
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x := make([]int64, 4)
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x[3] = 2
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y := [5]int64{1, 2, 3, 4, 5}
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z := "abcd"
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w := make([]byte, 4)
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w[3] = 5
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v := make(map[int]int64)
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v[3] = 18
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test(Index1(x), int64(2))
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test(Index1(y), int64(4))
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test(Index2(z), byte(100))
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test(Index2(w), byte(5))
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test(Index2a(w), byte(5))
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test(Index3(v), int64(18))
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test(Index4(v), int64(18))
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}
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