type of #expr argument in macro @a(int #expr) is ignored

[Book-reader]

the type should probably be either checked or disallowed.

fn void main()
{
  @a("hello");
}

macro @a(int #expr)
{
  io::printfn("Type of #expr was %s", $typeof(#expr).nameof);
}

 ~/code/c3 ❯ c3c compile-run test.c3

Program linked to executable 'test'.
Launching ./test
Type of #expr was String
Program completed with exit code 0.

[lerno]

This requires some change in the behaviour of #foo parameters.

1. Keep as today, but disallow compile time variable mutation (e.g. $a += 1 would not be accepted). This can be somewhat fragile and hard to track, but might work.
2. Keep as today but completely disallow compile time variables inside
3. Remove typing
4. Make #foo arguments always evaluate ONCE as a check, then this evaluation is copied 0 to n times, without actually evaluation compile time arguments again. This would mean that $a += 1 would evaluate exactly once regardless whether #foo is used or not. There are some possible questions as to whether this would remove some flexibility in foo.#bar constructs, but likely that would be possible to handle.

One of these should be selected, as otherwise the semantics will be hard to figure out for a reader, and it would be easy to make mistakes.