Expanding recurse EQUS "recurse" or recurse EQUS "\{recurse\}" hangs rgbasm

[Rangi42]

This was noted in #557:

tokens that end precisely at the end of an EQUS are not reported as coming from within the EQUS. It means that recurse EQUS "recurse" does infinitely hang RGBASM.

[Rangi42]

A more visible example: this stops after the recursion limit due to the newline at the end of recurse:

n = 0
recurse EQUS """
println n
n = n + 1
 recurse
"""
 recurse

But this recurses infinitely:

n = 0
recurse EQUS """
println n
n = n + 1
 recurse"""
 recurse

[Rangi42]

This problem exists with interpolation as well as EQUS expansion: recurse EQUS "\{recurse\}" will also loop forever.

I don't think it can happen with macro args (the third kind of expansion) because they can't be recursive.

[Rangi42]

#829 has some comments regarding a possible fix, if expansions stay unfreed even at the moment they're left, i.e. when exp->offset == exp->size. This would need to handle going back to the top-level correctly, and potentially free a whole nesting of expansions at once.