[Gcl-devel] SYMBOL-MACROLET problem

[Paul F. Dietz]

I wrote:

> I think the proper way to fix this is to rip out the PCL implementation
> of symbol-macrolet and instead do symbol-macrolet expansion in the same
> place ordinary macroexpansion is performed.  The PCL implementation is
> something of a hack, and I don't think it can be made correct in general
> (the generic problem is that it 'manually' macroexpands subterms during
> the code walk, but those subterms don't have symbol-macro substitution
> performed on them, so if the macro inspects the results of such expansion
> it sees the wrong thing.)

I've added a test that shows the problem in PCL's symbol-macrolet.
It's macrolet.13, in ansi-tests/macrolet.lsp.  The test is:

(deftest macrolet.13
  (symbol-macrolet ((a b))
    (macrolet ((foo (x &environment env)
                    (let ((y (macroexpand x env)))
                      (if (eq y 'a) 1 2))))
      (foo a)))
  2)

gcl expands FOO before substituting for A, and so incorrectly yields
1 instead of 2.

        Paul