TypedValue:
	int(typeId) Value
TypeDefinition:
	int(-typeId) encodingOfWireType
Value:
	SingletonValue | StructValue
SingletonValue:
	uint(0) FieldValue
FieldValue:
	builtinValue | ArrayValue | MapValue | SliceValue | StructValue | InterfaceValue
InterfaceValue:
	NilInterfaceValue | NonNilInterfaceValue
NilInterfaceValue:
	uint(0)
NonNilInterfaceValue:
	ConcreteTypeName TypeSequence InterfaceContents
ConcreteTypeName:

		// Convert extra from []int to []Value.
		e0 := make([]Value, len(test.extra))
		for j, e := range test.extra {
			e0[j] = ValueOf(e)
		}
		// Convert extra from []int to *SliceValue.
		e1 := ValueOf(test.extra)

		// Test Append.
		a0 := ValueOf(&test.orig).Elem()
		have0 := Append(a0, e0...)
		if have0.CanAddr() {
			t.Errorf("Append #%d: have slice should not be addressable", i)