testing/quick: support generation of array types in Value

Generating array types like [4]int would fail even though the int type
is generatable. Allow generating values of array types when the inner
type is generatable.

Change-Id: I7d71b3c18edb3737e2fec1ddf5e36c9dc8401971
Reviewed-on: https://go-review.googlesource.com/3865Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

src/testing/quick/quick.go

@@ -118,6 +118,14 @@ func Value(t reflect.Type, rand *rand.Rand) (value reflect.Value, ok bool) {
 			}
 			v.Index(i).Set(elem)
 		}
+	case reflect.Array:
+		for i := 0; i < v.Len(); i++ {
+			elem, ok := Value(concrete.Elem(), rand)
+			if !ok {
+				return reflect.Value{}, false
+			}
+			v.Index(i).Set(elem)
+		}
 	case reflect.String:
 		numChars := rand.Intn(complexSize)
 		codePoints := make([]rune, numChars)

src/testing/quick/quick_test.go

@@ -144,6 +144,12 @@ type TestIntptrAlias *int
 
 func fIntptrAlias(a TestIntptrAlias) TestIntptrAlias { return a }
 
+func fArray(a [4]byte) [4]byte { return a }
+
+type TestArrayAlias [4]byte
+
+func fArrayAlias(a TestArrayAlias) TestArrayAlias { return a }
+
 func reportError(property string, err error, t *testing.T) {
 	if err != nil {
 		t.Errorf("%s: %s", property, err)
@@ -195,6 +201,8 @@ func TestCheckEqual(t *testing.T) {
 	reportError("fUintptrAlias", CheckEqual(fUintptrAlias, fUintptrAlias, nil), t)
 	reportError("fIntptr", CheckEqual(fIntptr, fIntptr, nil), t)
 	reportError("fIntptrAlias", CheckEqual(fIntptrAlias, fIntptrAlias, nil), t)
+	reportError("fArray", CheckEqual(fArray, fArray, nil), t)
+	reportError("fArrayAlais", CheckEqual(fArrayAlias, fArrayAlias, nil), t)
 }
 
 // This tests that ArbitraryValue is working by checking that all the arbitrary