From 7faf72bd0d2124b799e397b08d37a11ed627bed3 Mon Sep 17 00:00:00 2001
From: Jonathan Allie <jonallie@google.com>
Date: Sat, 26 Apr 2014 10:25:16 -0600
Subject: [PATCH]       encoding/gob: handle interface types in isZero() by
 returning true for nil interfaces.

Fixes #7741.

LGTM=r
R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/96830044
---
 src/pkg/encoding/gob/encode.go         |  2 +-
 src/pkg/encoding/gob/gobencdec_test.go | 19 ++++++++++++++++---
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/pkg/encoding/gob/encode.go b/src/pkg/encoding/gob/encode.go
index d158b6442a..7831c02d13 100644
--- a/src/pkg/encoding/gob/encode.go
+++ b/src/pkg/encoding/gob/encode.go
@@ -491,7 +491,7 @@ func isZero(val reflect.Value) bool {
 		return !val.Bool()
 	case reflect.Complex64, reflect.Complex128:
 		return val.Complex() == 0
-	case reflect.Chan, reflect.Func, reflect.Ptr:
+	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Ptr:
 		return val.IsNil()
 	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
 		return val.Int() == 0
diff --git a/src/pkg/encoding/gob/gobencdec_test.go b/src/pkg/encoding/gob/gobencdec_test.go
index 0193e2b67d..157b7723a7 100644
--- a/src/pkg/encoding/gob/gobencdec_test.go
+++ b/src/pkg/encoding/gob/gobencdec_test.go
@@ -705,13 +705,14 @@ func TestGobEncoderExtraIndirect(t *testing.T) {
 }
 
 // Another bug: this caused a crash with the new Go1 Time type.
-// We throw in a gob-encoding array, to test another case of isZero
-
+// We throw in a gob-encoding array, to test another case of isZero,
+// and a struct containing an nil interface, to test a third.
 type isZeroBug struct {
 	T time.Time
 	S string
 	I int
 	A isZeroBugArray
+	F isZeroBugInterface
 }
 
 type isZeroBugArray [2]uint8
@@ -731,8 +732,20 @@ func (a *isZeroBugArray) GobDecode(data []byte) error {
 	return nil
 }
 
+type isZeroBugInterface struct {
+	I interface{}
+}
+
+func (i isZeroBugInterface) GobEncode() (b []byte, e error) {
+	return []byte{}, nil
+}
+
+func (i *isZeroBugInterface) GobDecode(data []byte) error {
+	return nil
+}
+
 func TestGobEncodeIsZero(t *testing.T) {
-	x := isZeroBug{time.Now(), "hello", -55, isZeroBugArray{1, 2}}
+	x := isZeroBug{time.Now(), "hello", -55, isZeroBugArray{1, 2}, isZeroBugInterface{}}
 	b := new(bytes.Buffer)
 	enc := NewEncoder(b)
 	err := enc.Encode(x)