codekingpro/portable-devtools

1// run2 3// Copyright 2021 The Go Authors. All rights reserved.4// Use of this source code is governed by a BSD-style5// license that can be found in the LICENSE file.6 7// Testing various generic uses of indexing, both for reads and writes.8 9package main10 11import "fmt"12 13// Can index an argument (read/write) constrained to be a slice or an array.14func Index1[T interface{ []int64 | [5]int64 }](x T) int64 {15	x[2] = 516	return x[3]17}18 19// Can index an argument (read) constrained to be a byte array or a string.20func Index2[T interface{ []byte | string }](x T) byte {21	return x[3]22}23 24// Can index an argument (write) constrained to be a byte array, but not a string.25func Index2a[T interface{ []byte }](x T) byte {26	x[2] = 'b'27	return x[3]28}29 30// Can index an argument (read/write) constrained to be a map. Maps can't31// be combined with any other type for indexing purposes.32func Index3[T interface{ map[int]int64 }](x T) int64 {33	x[2] = 4334	return x[3]35}36 37// But the type of the map keys or values can be parameterized.38func Index4[T any](x map[int]T) T {39	var zero T40	x[2] = zero41	return x[3]42}43 44func test[T comparable](got, want T) {45	if got != want {46		panic(fmt.Sprintf("got %v, want %v", got, want))47	}48}49 50func main() {51	x := make([]int64, 4)52	x[3] = 253	y := [5]int64{1, 2, 3, 4, 5}54	z := "abcd"55	w := make([]byte, 4)56	w[3] = 557	v := make(map[int]int64)58	v[3] = 1859 60	test(Index1(x), int64(2))61	test(Index1(y), int64(4))62	test(Index2(z), byte(100))63	test(Index2(w), byte(5))64	test(Index2a(w), byte(5))65	test(Index3(v), int64(18))66	test(Index4(v), int64(18))67}68