abcd crash on [foo>>(s), foo<<(s+s)]
[foo(x,y,z)] creates a multi-arc instead of a tuple

abcd substitues for loops variables:
net Foo (x) :
    buffer b : int = [x for x in range(4)]
                      ^     ^
                      substituted (should not)

errors during expressions evaluation are directly sent to user, should be wrapper to indicate this is a model error. And should be catched in abcd --simul/check
