PR# 19826 Invalid free operators but valid alias declarations

The compiler will reject invalid aliases such as:

~~~~~~~~~~~~
f alias ";": INTEGER
~~~~~~~~~~~~

But it accepts this one:

~~~~~~~~~~~~
g alias "∀": INTEGER
~~~~~~~~~~~~

even though it is not valid to write:

~~~~~~~~~~~~
i := ∀ foo
~~~~~~~~~~~~

I think that `alias "∀"` should be rejected by the compiler. Likewise, with the standard syntax level it is not possible anymore to write:

~~~~~~~~~~~~
i := @ foo
~~~~~~~~~~~~

So the following should be rejected by the compiler:

~~~~~~~~~~~~
g alias "@": INTEGER
~~~~~~~~~~~~

--
Eric Bezault