go/analysis/passes/directive: use strings.Cut

Change-Id: Ie3273daca752b8c22443edfdbde635a9f61577a3
GitHub-Last-Rev: 1e19b61
GitHub-Pull-Request: golang#450
Reviewed-on: https://go-review.googlesource.com/c/tools/+/530696
Reviewed-by: Tim King <taking@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: Tim King <taking@google.com>

Author: qiulaidongfeng

go/analysis/passes/directive/directive.go

@@ -124,7 +124,7 @@ func (check *checker) nonGoFile(pos token.Pos, fullText string) {
 	for text != "" {
 		offset := len(fullText) - len(text)
 		var line string
-		line, text, _ = stringsCut(text, "\n")
+		line, text, _ = strings.Cut(text, "\n")
 
 		if !inStar && strings.HasPrefix(line, "//") {
 			check.comment(pos+token.Pos(offset), line)
@@ -137,7 +137,7 @@ func (check *checker) nonGoFile(pos token.Pos, fullText string) {
 			line = strings.TrimSpace(line)
 			if inStar {
 				var ok bool
-				_, line, ok = stringsCut(line, "*/")
+				_, line, ok = strings.Cut(line, "*/")
 				if !ok {
 					break
 				}
@@ -200,14 +200,6 @@ func (check *checker) comment(pos token.Pos, line string) {
 	}
 }
 
-// Go 1.18 strings.Cut.
-func stringsCut(s, sep string) (before, after string, found bool) {
-	if i := strings.Index(s, sep); i >= 0 {
-		return s[:i], s[i+len(sep):], true
-	}
-	return s, "", false
-}
-
 // Go 1.20 strings.CutPrefix.
 func stringsCutPrefix(s, prefix string) (after string, found bool) {
 	if !strings.HasPrefix(s, prefix) {