// The returned encoder only checks CanAddr when allowAddr is true.
func newTypeEncoder(t reflect.Type, allowAddr bool) encoderFunc {
	// If we have a non-pointer value whose type implements
	// Marshaler with a value receiver, then we're better off taking
	// the address of the value - otherwise we end up with an
	// allocation as we cast the value to an interface.
	if t.Kind() != reflect.Pointer && allowAddr && reflect.PointerTo(t).Implements(marshalerType) {