From cb6cb42ede03d6a35fbe6603f22e8855910f9f51 Mon Sep 17 00:00:00 2001
From: Keith Randall <khr@golang.org>
Date: Tue, 20 May 2014 16:26:04 -0700
Subject: [PATCH] reflect: don't panic on delete from nil map.

Fixes #8051

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/95560046
---
 src/pkg/reflect/all_test.go | 3 +++
 src/pkg/runtime/hashmap.goc | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/pkg/reflect/all_test.go b/src/pkg/reflect/all_test.go
index 9c5eb4e554..e9949012c4 100644
--- a/src/pkg/reflect/all_test.go
+++ b/src/pkg/reflect/all_test.go
@@ -993,6 +993,9 @@ func TestNilMap(t *testing.T) {
 	if x.Kind() != Invalid {
 		t.Errorf("mbig.MapIndex(\"hello\") for nil map = %v, want Invalid Value", x)
 	}
+
+	// Test that deletes from a nil map succeed.
+	mv.SetMapIndex(ValueOf("hi"), Value{})
 }
 
 func TestChan(t *testing.T) {
diff --git a/src/pkg/runtime/hashmap.goc b/src/pkg/runtime/hashmap.goc
index 36707c6ede..3327bed65e 100644
--- a/src/pkg/runtime/hashmap.goc
+++ b/src/pkg/runtime/hashmap.goc
@@ -990,7 +990,7 @@ func reflect·mapassign(t *MapType, h *Hmap, key *byte, val *byte) {
 #pragma textflag NOSPLIT
 func reflect·mapdelete(t *MapType, h *Hmap, key *byte) {
 	if(h == nil)
-		runtime·panicstring("delete from nil map");
+		return; // see bug 8051
 	if(raceenabled) {
 		runtime·racewritepc(h, runtime·getcallerpc(&t), reflect·mapdelete);
 		runtime·racereadobjectpc(key, t->key, runtime·getcallerpc(&t), reflect·mapdelete);