Attached is a new paper addressing how the P2237/P2230 facilities might be expanded to be able handle the `Sum<T,U>` example discussed awhile back, and more generally subsume the capabilities of the "string-injection" approach, while avoiding its drawbacks.

Basically: `consteval {}` in more contexts (e.g. constructor initializer lists), and generalize the fragment syntax to allow for new fragment types (e.g. constructor initializer fragments).

I am attaching the markdown file as well for easier copying and pasting, e.g. to tweak the syntax of the examples for use in alternative proposals.

I haven’t yet figured out how to get a P number and put this on isocpp, but wanted to get this draft out before the weekend to give ample time for consideration before the upcoming meeting.

Thanks,

Dave