From c017d4c7c1bc1f8cd39e6c70b60885cef1231dcd Mon Sep 17 00:00:00 2001
From: Eduard Bondarenko <eduardbcom@gmail.com>
Date: Fri, 24 Jul 2020 16:52:53 +0300
Subject: [PATCH] regexp: improve Regexp.ReplaceAll documentation and tests
 related to Expand part

Fixes #40329
---
 src/regexp/example_test.go | 14 ++++++++++++++
 src/regexp/regexp.go       |  8 ++++----
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/src/regexp/example_test.go b/src/regexp/example_test.go
index 466b38b0fa2aa4..707445f9ff02f7 100644
--- a/src/regexp/example_test.go
+++ b/src/regexp/example_test.go
@@ -228,11 +228,18 @@ func ExampleRegexp_ReplaceAll() {
 	fmt.Printf("%s\n", re.ReplaceAll([]byte("-ab-axxb-"), []byte("$1")))
 	fmt.Printf("%s\n", re.ReplaceAll([]byte("-ab-axxb-"), []byte("$1W")))
 	fmt.Printf("%s\n", re.ReplaceAll([]byte("-ab-axxb-"), []byte("${1}W")))
+
+	re2 := regexp.MustCompile(`a(?P<1W>x*)b`)
+	fmt.Printf("%s\n", re2.ReplaceAll([]byte("-ab-axxb-"), []byte("$1W")))
+	fmt.Printf("%s\n", re2.ReplaceAll([]byte("-ab-axxb-"), []byte("${1}W")))
+
 	// Output:
 	// -T-T-
 	// --xx-
 	// ---
 	// -W-xxW-
+	// --xx-
+	// -W-xxW-
 }
 
 func ExampleRegexp_ReplaceAllLiteralString() {
@@ -252,11 +259,18 @@ func ExampleRegexp_ReplaceAllString() {
 	fmt.Println(re.ReplaceAllString("-ab-axxb-", "$1"))
 	fmt.Println(re.ReplaceAllString("-ab-axxb-", "$1W"))
 	fmt.Println(re.ReplaceAllString("-ab-axxb-", "${1}W"))
+
+	re2 := regexp.MustCompile(`a(?P<1W>x*)b`)
+	fmt.Printf("%s\n", re2.ReplaceAllString("-ab-axxb-", "$1W"))
+	fmt.Println(re.ReplaceAllString("-ab-axxb-", "${1}W"))
+
 	// Output:
 	// -T-T-
 	// --xx-
 	// ---
 	// -W-xxW-
+	// --xx-
+	// -W-xxW-
 }
 
 func ExampleRegexp_ReplaceAllStringFunc() {
diff --git a/src/regexp/regexp.go b/src/regexp/regexp.go
index 1c9b2fd4de43ee..3752b467c63e93 100644
--- a/src/regexp/regexp.go
+++ b/src/regexp/regexp.go
@@ -573,8 +573,8 @@ func Match(pattern string, b []byte) (matched bool, err error) {
 }
 
 // ReplaceAllString returns a copy of src, replacing matches of the Regexp
-// with the replacement string repl. Inside repl, $ signs are interpreted as
-// in Expand, so for instance $1 represents the text of the first submatch.
+// with the replacement string repl.
+// Inside repl, $ signs are interpreted as in Expand.
 func (re *Regexp) ReplaceAllString(src, repl string) string {
 	n := 2
 	if strings.Contains(repl, "$") {
@@ -672,8 +672,8 @@ func (re *Regexp) replaceAll(bsrc []byte, src string, nmatch int, repl func(dst
 }
 
 // ReplaceAll returns a copy of src, replacing matches of the Regexp
-// with the replacement text repl. Inside repl, $ signs are interpreted as
-// in Expand, so for instance $1 represents the text of the first submatch.
+// with the replacement text repl.
+// Inside repl, $ signs are interpreted as in Expand.
 func (re *Regexp) ReplaceAll(src, repl []byte) []byte {
 	n := 2
 	if bytes.IndexByte(repl, '$') >= 0 {