Do not use custom format for nil slice (#201)

The custom diff output for slices does not accurately reflect the minute
differences between a nil slice and an empty slice.
Avoid the custom diffing if either value is nil.

1 files changed, 38 insertions, 0 deletions

diff --git a/cmp/compare_test.go b/cmp/compare_test.go
index a08df1b..f305b80 100644
--- a/cmp/compare_test.go
+++ b/cmp/compare_test.go
@@ -905,6 +905,44 @@ using the AllowUnexported option.`, "\n"),
 		},
 		wantEqual: false,
 		reason:    "batched per-line diff desired since string looks like multi-line textual data",
+	}, {
+		label: label,
+		x: MyComposite{
+			BytesA:  []byte{1, 2, 3},
+			BytesB:  []MyByte{4, 5, 6},
+			BytesC:  MyBytes{7, 8, 9},
+			IntsA:   []int8{-1, -2, -3},
+			IntsB:   []MyInt{-4, -5, -6},
+			IntsC:   MyInts{-7, -8, -9},
+			UintsA:  []uint16{1000, 2000, 3000},
+			UintsB:  []MyUint{4000, 5000, 6000},
+			UintsC:  MyUints{7000, 8000, 9000},
+			FloatsA: []float32{1.5, 2.5, 3.5},
+			FloatsB: []MyFloat{4.5, 5.5, 6.5},
+			FloatsC: MyFloats{7.5, 8.5, 9.5},
+		},
+		y:         MyComposite{},
+		wantEqual: false,
+		reason:    "batched diffing for non-nil slices and nil slices",
+	}, {
+		label: label,
+		x: MyComposite{
+			BytesA:  []byte{},
+			BytesB:  []MyByte{},
+			BytesC:  MyBytes{},
+			IntsA:   []int8{},
+			IntsB:   []MyInt{},
+			IntsC:   MyInts{},
+			UintsA:  []uint16{},
+			UintsB:  []MyUint{},
+			UintsC:  MyUints{},
+			FloatsA: []float32{},
+			FloatsB: []MyFloat{},
+			FloatsC: MyFloats{},
+		},
+		y:         MyComposite{},
+		wantEqual: false,
+		reason:    "batched diffing for empty slices and nil slices",
 	}}
 }