[Oberon] Conditional compilation using IF const THEN

[Andreas Pirklbauer]

   > A) add code to only parse. Something like a clever SkipUntilMatchingEnd(). It has to handle nesting. 
   > B) influence code generation if the IF-condition is constant. Not very elegant code ..

This is, perhaps, one of the reasons why the IF optimization has not been carried forward
from the previous (multi-pass) compilers to the (first) single-pass M2 compiler back in ’84.

If someone forced me to introduce the IF optimization, I’d probably pick variant A. At
least then one can “offload/hide the inelegance" to SkipUntilMatchingEnd..

Generally though, I believe this would be optimization at the wrong place. The compiler is not
not here to correct bad programming habits.

And if I really wanted to implement *conditional compilation*, I would not use the IF language
construct for that, but something else, e.g. a compiler directive #IF or something. Not great
either IMHO. And of course not common at all in Wirthian compilers, to say the least..