Re: false warnings when compiling with lexical-binding and cl-lib.

[Thierry Volpiatto <thierry.volpiatto@gmail.com>]

Thierry Volpiatto <thierry.volpiatto@gmail.com> writes:

> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>
>>> This patch avoid adding a new binding by the 'into' clause when the
>>> binding have been already added by a 'with' clause.
>>> I wonder if this is correct, real common-lisp return an error in such
>>> case, WDYT?
>>
>> Oh, wait, then the warning is OK.  It indicates that the `with lst' is
>> extraneous and unused.  IOW, there's no bug to fix.  We could change
>> cl-loop to signal an error, but it doesn't seem to be worth the trouble.
>
> Yes, maybe the error message can be a little more explicit, common-lisp send a
> message like this:
>
> ,----
> |  Variable LST in INTO clause is a duplicate
> | current LOOP context: COLLECT I INTO LST FINALLY.
> |    [Condition of type SB-INT:COMPILED-PROGRAM-ERROR]
> `----
>
> Also the warning is only at compile time, should we return an error on
> evaluation ?
> This can be detected and handled from the same function 
> i.e (cl--loop-handle-accum)

--8<---------------cut here---------------start------------->8---
diff --git a/lisp/emacs-lisp/cl-macs.el b/lisp/emacs-lisp/cl-macs.el
index 2209297..3faf23b 100644
--- a/lisp/emacs-lisp/cl-macs.el
+++ b/lisp/emacs-lisp/cl-macs.el
@@ -1564,9 +1564,13 @@ If BODY is `setq', then use SPECS for assignments rather than for bindings."
 
 (defun cl--loop-handle-accum (def &optional func) ; uses loop-*
   (if (eq (car cl--loop-args) 'into)
-      (let ((var (cl--pop2 cl--loop-args)))
+      (let* ((var (cl--pop2 cl--loop-args))
+             (binding (list (list var def))))
 	(or (memq var cl--loop-accum-vars)
-	    (progn (push (list (list var def)) cl--loop-bindings)
+            (cl-assert (not (member binding cl--loop-bindings))
+                       nil "Variable %s in INTO clause is a duplicate"
+                       (upcase (symbol-name (caar binding))))
+	    (progn (push binding cl--loop-bindings)
 		   (push var cl--loop-accum-vars)))
 	var)
     (or cl--loop-accum-var
--8<---------------cut here---------------end--------------->8---

-- 
Thierry
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