Jeremy Ong wrote:
> Thinking outloud, as an example, we might declare:
>
> template <bool>
> class Serializable {};
>
> And later use this class as a decorator like so:
>
> struct Foo
> {
>     @Serializable<true>
>     int data;
> }:

We can do this, but it isn't necessary. @type is not
substantially easier to implement than @expr, so we
can just do

struct serializable
{
    bool value;
};

struct Foo
{
    @serializable(true)
    int data;
};

instead.