Revert "testing/quick: generate more map and slice states"

This reverts commit 0ccabe2e0b42a2602e0f37ce28d5368aa811f530.

Change-Id: Ib1c230fb6801c0ee26f4a352b0c1130fa240a76a
Reviewed-on: https://go-review.googlesource.com/22860
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

2 files changed, 35 insertions, 29 deletions

diff --git a/src/testing/quick/quick.go b/src/testing/quick/quick.go
index 4bc8e3fc2e..798d41aa7d 100644
--- a/src/testing/quick/quick.go
+++ b/src/testing/quick/quick.go
@@ -14,7 +14,7 @@ import (
 	"strings"
 )
 
-var defaultMaxCount = flag.Int("quickchecks", 100, "The default number of iterations for each check")
+var defaultMaxCount *int = flag.Int("quickchecks", 100, "The default number of iterations for each check")
 
 // A Generator can generate random values of its own type.
 type Generator interface {
@@ -98,22 +98,18 @@ func sizedValue(t reflect.Type, rand *rand.Rand, size int) (value reflect.Value,
 	case reflect.Uintptr:
 		v.SetUint(uint64(randInt64(rand)))
 	case reflect.Map:
-		if generateNilValue(rand) {
-			v.Set(reflect.Zero(concrete)) // Generate nil map.
-		} else {
-			numElems := rand.Intn(size)
-			v.Set(reflect.MakeMap(concrete))
-			for i := 0; i < numElems; i++ {
-				key, ok1 := sizedValue(concrete.Key(), rand, size)
-				value, ok2 := sizedValue(concrete.Elem(), rand, size)
-				if !ok1 || !ok2 {
-					return reflect.Value{}, false
-				}
-				v.SetMapIndex(key, value)
+		numElems := rand.Intn(size)
+		v.Set(reflect.MakeMap(concrete))
+		for i := 0; i < numElems; i++ {
+			key, ok1 := sizedValue(concrete.Key(), rand, size)
+			value, ok2 := sizedValue(concrete.Elem(), rand, size)
+			if !ok1 || !ok2 {
+				return reflect.Value{}, false
 			}
+			v.SetMapIndex(key, value)
 		}
 	case reflect.Ptr:
-		if generateNilValue(rand) {
+		if rand.Intn(size) == 0 {
 			v.Set(reflect.Zero(concrete)) // Generate nil pointer.
 		} else {
 			elem, ok := sizedValue(concrete.Elem(), rand, size)
@@ -124,20 +120,15 @@ func sizedValue(t reflect.Type, rand *rand.Rand, size int) (value reflect.Value,
 			v.Elem().Set(elem)
 		}
 	case reflect.Slice:
-		if generateNilValue(rand) {
-			v.Set(reflect.Zero(concrete)) // Generate nil slice.
-		} else {
-			slCap := rand.Intn(size)
-			slLen := rand.Intn(slCap + 1)
-			sizeLeft := size - slCap
-			v.Set(reflect.MakeSlice(concrete, slLen, slCap))
-			for i := 0; i < slLen; i++ {
-				elem, ok := sizedValue(concrete.Elem(), rand, sizeLeft)
-				if !ok {
-					return reflect.Value{}, false
-				}
-				v.Index(i).Set(elem)
+		numElems := rand.Intn(size)
+		sizeLeft := size - numElems
+		v.Set(reflect.MakeSlice(concrete, numElems, numElems))
+		for i := 0; i < numElems; i++ {
+			elem, ok := sizedValue(concrete.Elem(), rand, sizeLeft)
+			if !ok {
+				return reflect.Value{}, false
 			}
+			v.Index(i).Set(elem)
 		}
 	case reflect.Array:
 		for i := 0; i < v.Len(); i++ {
@@ -385,5 +376,3 @@ func toString(interfaces []interface{}) string {
 	}
 	return strings.Join(s, ", ")
 }
-
-func generateNilValue(r *rand.Rand) bool { return r.Intn(20) == 0 }
diff --git a/src/testing/quick/quick_test.go b/src/testing/quick/quick_test.go
index 018ece2a52..fe443592f8 100644
--- a/src/testing/quick/quick_test.go
+++ b/src/testing/quick/quick_test.go
@@ -290,3 +290,20 @@ func TestMutuallyRecursive(t *testing.T) {
 	f := func(a A) bool { return true }
 	Check(f, nil)
 }
+
+// Some serialization formats (e.g. encoding/pem) cannot distinguish
+// between a nil and an empty map or slice, so avoid generating the
+// zero value for these.
+func TestNonZeroSliceAndMap(t *testing.T) {
+	type Q struct {
+		M map[int]int
+		S []int
+	}
+	f := func(q Q) bool {
+		return q.M != nil && q.S != nil
+	}
+	err := Check(f, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+}