5 files changed, 9 insertions, 9 deletions
diff --git a/src/encoding/csv/writer.go b/src/encoding/csv/writer.go
index 353d91f238..a6056285b4 100644
--- a/src/encoding/csv/writer.go
+++ b/src/encoding/csv/writer.go
@@ -130,7 +130,7 @@ func (w *Writer) fieldNeedsQuotes(field string) bool {
 	if field == "" {
 		return false
 	}
-	if field == `\.` || strings.IndexRune(field, w.Comma) >= 0 || strings.IndexAny(field, "\"\r\n") >= 0 {
+	if field == `\.` || strings.ContainsRune(field, w.Comma) || strings.ContainsAny(field, "\"\r\n") {
 		return true
 	}
 
diff --git a/src/encoding/gob/codec_test.go b/src/encoding/gob/codec_test.go
index 8efcdc78ff..b772171f93 100644
--- a/src/encoding/gob/codec_test.go
+++ b/src/encoding/gob/codec_test.go
@@ -970,7 +970,7 @@ func TestBadRecursiveType(t *testing.T) {
 	err := NewEncoder(b).Encode(&rec)
 	if err == nil {
 		t.Error("expected error; got none")
-	} else if strings.Index(err.Error(), "recursive") < 0 {
+	} else if !strings.Contains(err.Error(), "recursive") {
 		t.Error("expected recursive type error; got", err)
 	}
 	// Can't test decode easily because we can't encode one, so we can't pass one to a Decoder.
diff --git a/src/encoding/gob/encoder_test.go b/src/encoding/gob/encoder_test.go
index 570d79696b..811dd2b18c 100644
--- a/src/encoding/gob/encoder_test.go
+++ b/src/encoding/gob/encoder_test.go
@@ -280,7 +280,7 @@ func TestValueError(t *testing.T) {
 	}
 	t4p := &Type4{3}
 	var t4 Type4 // note: not a pointer.
-	if err := encAndDec(t4p, t4); err == nil || strings.Index(err.Error(), "pointer") < 0 {
+	if err := encAndDec(t4p, t4); err == nil || !strings.Contains(err.Error(), "pointer") {
 		t.Error("expected error about pointer; got", err)
 	}
 }
@@ -388,7 +388,7 @@ func TestSingletons(t *testing.T) {
 			t.Errorf("expected error decoding %v: %s", test.in, test.err)
 			continue
 		case err != nil && test.err != "":
-			if strings.Index(err.Error(), test.err) < 0 {
+			if !strings.Contains(err.Error(), test.err) {
 				t.Errorf("wrong error decoding %v: wanted %s, got %v", test.in, test.err, err)
 			}
 			continue
@@ -414,7 +414,7 @@ func TestStructNonStruct(t *testing.T) {
 	var ns NonStruct
 	if err := encAndDec(s, &ns); err == nil {
 		t.Error("should get error for struct/non-struct")
-	} else if strings.Index(err.Error(), "type") < 0 {
+	} else if !strings.Contains(err.Error(), "type") {
 		t.Error("for struct/non-struct expected type error; got", err)
 	}
 	// Now try the other way
@@ -424,7 +424,7 @@ func TestStructNonStruct(t *testing.T) {
 	}
 	if err := encAndDec(ns, &s); err == nil {
 		t.Error("should get error for non-struct/struct")
-	} else if strings.Index(err.Error(), "type") < 0 {
+	} else if !strings.Contains(err.Error(), "type") {
 		t.Error("for non-struct/struct expected type error; got", err)
 	}
 }
diff --git a/src/encoding/gob/gobencdec_test.go b/src/encoding/gob/gobencdec_test.go
index eb76b481d1..d674f0c784 100644
--- a/src/encoding/gob/gobencdec_test.go
+++ b/src/encoding/gob/gobencdec_test.go
@@ -548,7 +548,7 @@ func TestGobEncoderFieldTypeError(t *testing.T) {
 	if err == nil {
 		t.Fatal("expected decode error for mismatched fields (encoder to non-decoder)")
 	}
-	if strings.Index(err.Error(), "type") < 0 {
+	if !strings.Contains(err.Error(), "type") {
 		t.Fatal("expected type error; got", err)
 	}
 	// Non-encoder to GobDecoder: error
@@ -562,7 +562,7 @@ func TestGobEncoderFieldTypeError(t *testing.T) {
 	if err == nil {
 		t.Fatal("expected decode error for mismatched fields (non-encoder to decoder)")
 	}
-	if strings.Index(err.Error(), "type") < 0 {
+	if !strings.Contains(err.Error(), "type") {
 		t.Fatal("expected type error; got", err)
 	}
 }
diff --git a/src/encoding/xml/marshal.go b/src/encoding/xml/marshal.go
index 8ebd693030..9fcd5d7695 100644
--- a/src/encoding/xml/marshal.go
+++ b/src/encoding/xml/marshal.go
@@ -850,7 +850,7 @@ func (p *printer) marshalStruct(tinfo *typeInfo, val reflect.Value) error {
 			switch k {
 			case reflect.String:
 				s := vf.String()
-				dashDash = strings.Index(s, "--") >= 0
+				dashDash = strings.Contains(s, "--")
 				dashLast = s[len(s)-1] == '-'
 				if !dashDash {
 					p.WriteString(s)