From b2aad2c9a95d14eb978f29baa6e3a5c3c20eef30 Mon Sep 17 00:00:00 2001
From: motomux <motomux@gmail.com>
Date: Fri, 9 Dec 2016 12:52:51 -0800
Subject: [PATCH] Diff nil and empty for slice and map

---
 diff.go      | 8 ++++++++
 diff_test.go | 4 ++++
 2 files changed, 12 insertions(+)

diff --git a/diff.go b/diff.go
index 6aa7f74..125e7eb 100644
--- a/diff.go
+++ b/diff.go
@@ -142,6 +142,10 @@ func (w diffPrinter) diff(av, bv reflect.Value) {
 			w := w.relabel(fmt.Sprintf("[%#v]", k))
 			w.printf("(missing) != %q", bv.MapIndex(k))
 		}
+		if av.IsNil() != bv.IsNil() {
+			w.printf("%#v != %#v", av, bv)
+			break
+		}
 	case reflect.Ptr:
 		switch {
 		case av.IsNil() && !bv.IsNil():
@@ -161,6 +165,10 @@ func (w diffPrinter) diff(av, bv reflect.Value) {
 		for i := 0; i < lenA; i++ {
 			w.relabel(fmt.Sprintf("[%d]", i)).diff(av.Index(i), bv.Index(i))
 		}
+		if av.IsNil() != bv.IsNil() {
+			w.printf("%#v != %#v", av, bv)
+			break
+		}
 	case reflect.String:
 		if a, b := av.String(), bv.String(); a != b {
 			w.printf("%q != %q", a, b)
diff --git a/diff_test.go b/diff_test.go
index a951e4b..7e14798 100644
--- a/diff_test.go
+++ b/diff_test.go
@@ -40,6 +40,8 @@ var (
 	f1 = func() {}
 	i0 = 0
 	i1 = 1
+	s0 []int
+	m0 map[int]int
 )
 
 var diffs = []difftest{
@@ -126,6 +128,8 @@ var diffs = []difftest{
 		struct{ x unsafe.Pointer }{unsafe.Pointer(uintptr(1))},
 		[]string{`x: 0x0 != 0x1`},
 	},
+	{[]int{}, s0, []string{"[]int{} != []int(nil)"}},
+	{map[int]int{}, m0, []string{"map[int]int{} != map[int]int(nil)"}},
 }
 
 func TestDiff(t *testing.T) {