op: bug in do: must insert @1 into unexpanded form.

In the case when the do syntax has no metavariables, and it
expands as-is without the addition of symbol in the tail
position, we are doing something wrong: we are adding the
@1 into the expanded version of the form, rather than
the original. For instance:

  1> (expand '(do pop a))
  (lambda (#:arg-1-0017 . #:arg-rest-0016)
    (prog1 (car a)
      (sys:setq a (cdr a))
      #:arg-1-0017))

Here, the @1 was inserted into the (prog1 ...) form
which is the expansion of pop. This is incorrect;
it must be inserted into the original (pop a)
syntax as (pop a @1).

* op.tl (op-expand): In this case when there are no
metas and no do-gen that can be replaced by @1 via
symacrolet, go back to the original args syntax,
add the arg1 meta into that syntax, and process it
from the beginning through parallel expansions
steps.

* tests/012/op.tl: Couple of tests added.

1 files changed, 5 insertions, 0 deletions

diff --git a/tests/012/op.tl b/tests/012/op.tl
index 0fffb6ee..12969dcc 100644
--- a/tests/012/op.tl
+++ b/tests/012/op.tl
@@ -40,6 +40,11 @@
   (fi (do if @42 @rest)) (42 t)
   (fi (do if @1 @3 @rest @2)) (3 t))
 
+(mtest
+  [(do quote x) 3] :error
+  [(do quote @1) 3] :error
+  (do pop a) :error)
+
 (defun y (f)
   [(op @1 @1)
    (op f (op [@@1 @@1]))])