reflect: uncomment TestAppend and fix a bug it found

src/reflect/all_test.go

@@ -874,8 +874,6 @@ var appendTests = []struct {
 	{make([]int, 2, 4), []int{22, 33, 44}},
 }
 
-/*
-
 func TestAppend(t *testing.T) {
 	for i, test := range appendTests {
 		origLen, extraLen := len(test.orig), len(test.extra)
@@ -935,8 +933,6 @@ func TestAppend(t *testing.T) {
 	}
 }
 
-*/
-
 func TestCopy(t *testing.T) {
 	a := []int{1, 2, 3, 4, 10, 9, 8, 7}
 	b := []int{11, 22, 33, 44, 1010, 99, 88, 77, 66, 55, 44}

src/reflect/value.go

@@ -1666,6 +1666,7 @@ func (v *Value) extendSlice(n int) {
 		cap:  ncap,
 	}
 
+	v.flags = valueFlagExported
 	v.value = (unsafe.Pointer)(&newslice)
 }