//go:build go1.mn comment directives don't work with Go toolchain v1.22.x versions when no go.mod files are involved
for-range and tranditional for;; loops. Since the semantic changes alter the behavior of existing code written according to the previous semantics, they break backward compatibility.
for-range loops are almost unaffected, traditional for;; loops exhibit unexpected behaviors due to the breakage.
//go:build go1.21 comment directive at the beginning of the Go source file containing the old code.
go.mod file, the //go:build go1.mn comment directive in it fails to specify the Go verison for it.
//go:build go1.21
package main
import "fmt"
func filter(n int) bool {
return n&3 == 1
}
// Search values and return them without perversing order.
func search(start, end int) (r []int) {
var count = 0
for i, index := start, 0; i <= end; i++ {
if filter(i) {
count++
defer func(value int) {
r[index] = value
index++
}(i)
}
}
r = make([]int, count)
return
}
go run command (without a go.mod file involved), the example program prints [13 0] with Go toolchain 1.22.x versions, due to Go 1.22+ semantics are used, which is wrongly. It should prints [17 13], as with older and newer toolchain versions.
$ gotv 1.21. run example.go [Run]: $HOME/.cache/gotv/tag_go1.21.12/bin/go run aa.go [17 13] $ gotv 1.22. run example.go [Run]: $HOME/.cache/gotv/tag_go1.22.5/bin/go run aa.go [13 0] $ gotv 1.23. run example.go [Run]: $HOME/.cache/gotv/tag_go1.23rc1/bin/go run aa.go [17 13]
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