Constexpr evaluation of user-defined functions

[Sainan]

For example:

local function add(a, b)
    return a + b
end
print($add(1, 2))

Should compile as if

print(3)

was written.

Although, for this to work we should maybe first figure out how to get this to work:

print($(1 + 2))

However, the main reason I suggest this is because I'd want something similar to the power of macros in Pluto for meta-programming.

[Sainan]

I think this is a bit too broad, I'll try to narrow down the exact use cases and track that in new issues.