From f408d0f37b425271be02049495ca47a54028b35d Mon Sep 17 00:00:00 2001
From: Shivaram Lingamneni <slingamn@cs.stanford.edu>
Date: Wed, 23 May 2018 15:39:30 -0400
Subject: [PATCH] review fix: add nil receivers to other read-only ModeSet
 methods

---
 irc/modes/modes.go      | 23 ++++++++++++++++-------
 irc/modes/modes_test.go | 13 +++++++++++++
 2 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/irc/modes/modes.go b/irc/modes/modes.go
index 19328457..310e46f4 100644
--- a/irc/modes/modes.go
+++ b/irc/modes/modes.go
@@ -366,6 +366,10 @@ func (set *ModeSet) SetMode(mode Mode, on bool) (applied bool) {
 
 // return the modes in the set as a slice
 func (set *ModeSet) AllModes() (result []Mode) {
+	if set == nil {
+		return
+	}
+
 	set.RLock()
 	defer set.RUnlock()
 
@@ -376,22 +380,27 @@ func (set *ModeSet) AllModes() (result []Mode) {
 }
 
 // String returns the modes in this set.
-func (set *ModeSet) String() string {
+func (set *ModeSet) String() (result string) {
+	if set == nil {
+		return
+	}
+
 	set.RLock()
 	defer set.RUnlock()
 
-	if len(set.modes) == 0 {
-		return ""
-	}
-	var result []byte
+	var buf strings.Builder
 	for mode := range set.modes {
-		result = append(result, mode.String()...)
+		buf.WriteRune(rune(mode))
 	}
-	return string(result)
+	return buf.String()
 }
 
 // Prefixes returns a list of prefixes for the given set of channel modes.
 func (set *ModeSet) Prefixes(isMultiPrefix bool) (prefixes string) {
+	if set == nil {
+		return
+	}
+
 	set.RLock()
 	defer set.RUnlock()
 
diff --git a/irc/modes/modes_test.go b/irc/modes/modes_test.go
index 8f20bdfc..216add3c 100644
--- a/irc/modes/modes_test.go
+++ b/irc/modes/modes_test.go
@@ -35,3 +35,16 @@ func TestSetMode(t *testing.T) {
 		t.Errorf("unexpected modestring: %s", modeString)
 	}
 }
+
+func TestNilReceivers(t *testing.T) {
+	var set ModeSet
+
+	if set.HasMode(Invisible) {
+		t.Errorf("nil ModeSet should not have any modes")
+	}
+
+	str := set.String()
+	if str != "" {
+		t.Errorf("nil Modeset should have empty String(), got %v instead", str)
+	}
+}