From 7cd7f340e2cac31e7ea312dbadc83f6d71c15d04 Mon Sep 17 00:00:00 2001
From: Cristian Angelini <cristian.angelini@rocket-internet.de>
Date: Tue, 14 Nov 2017 13:33:52 +0100
Subject: [PATCH] Fixes slices equality, when slices are extracted from the
 same array

---
 deep.go      |  7 +++---
 deep_test.go | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+), 3 deletions(-)

diff --git a/deep.go b/deep.go
index 2fd634d..c7eceb0 100644
--- a/deep.go
+++ b/deep.go
@@ -257,12 +257,13 @@ func (c *cmp) equals(a, b reflect.Value, level int) {
 			return
 		}
 
-		if a.Pointer() == b.Pointer() {
+		aLen := a.Len()
+		bLen := b.Len()
+
+		if a.Pointer() == b.Pointer() && aLen == bLen {
 			return
 		}
 
-		aLen := a.Len()
-		bLen := b.Len()
 		n := aLen
 		if bLen > aLen {
 			n = bLen
diff --git a/deep_test.go b/deep_test.go
index 9bd54e8..78ed6cf 100644
--- a/deep_test.go
+++ b/deep_test.go
@@ -539,6 +539,77 @@ func TestSlice(t *testing.T) {
 	}
 }
 
+func TestSiblingSlices(t *testing.T) {
+	father := []int{1, 2, 3, 4}
+	a := father[0:3]
+	b := father[0:3]
+
+	diff := deep.Equal(a, b)
+	if len(diff) > 0 {
+		t.Error("should be equal:", diff)
+	}
+	diff = deep.Equal(b, a)
+	if len(diff) > 0 {
+		t.Error("should be equal:", diff)
+	}
+
+	a = father[0:3]
+	b = father[0:2]
+	diff = deep.Equal(a, b)
+	if diff == nil {
+		t.Fatal("no diff")
+	}
+	if len(diff) != 1 {
+		t.Error("too many diff:", diff)
+	}
+	if diff[0] != "slice[2]: 3 != <no value>" {
+		t.Error("wrong diff:", diff[0])
+	}
+
+	a = father[0:2]
+	b = father[0:3]
+
+	diff = deep.Equal(a, b)
+	if diff == nil {
+		t.Fatal("no diff")
+	}
+	if len(diff) != 1 {
+		t.Error("too many diff:", diff)
+	}
+	if diff[0] != "slice[2]: <no value> != 3" {
+		t.Error("wrong diff:", diff[0])
+	}
+
+	a = father[0:2]
+	b = father[2:4]
+
+	diff = deep.Equal(a, b)
+	if diff == nil {
+		t.Fatal("no diff")
+	}
+	if len(diff) != 2 {
+		t.Error("too many diff:", diff)
+	}
+	if diff[0] != "slice[0]: 1 != 3" {
+		t.Error("wrong diff:", diff[0])
+	}
+	if diff[1] != "slice[1]: 2 != 4" {
+		t.Error("wrong diff:", diff[1])
+	}
+
+	a = father[0:0]
+	b = father[1:1]
+
+	diff = deep.Equal(a, b)
+	if len(diff) > 0 {
+		t.Error("should be equal:", diff)
+	}
+	diff = deep.Equal(b, a)
+	if len(diff) > 0 {
+		t.Error("should be equal:", diff)
+	}
+}
+
 func TestPointer(t *testing.T) {
 	type T struct {
 		i int