Re: defvar inside let-binding

[Lars Magne Ingebrigtsen <larsi@gnus.org>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> Yes, just like with defvar.  The difference is that defvar detects the
> problem and outputs a warning.

Ah, ok.  So if we decide to change the way let-bindings affect defvar
when we load files, then we have to basically implement the same
detection for defcustom.

Which we probably should do anyway.  :-)

It's this code, right?

      if (NILP (tem))
	Fset_default (sym, eval_sub (Fcar (tail)));
      else
	{ /* Check if there is really a global binding rather than just a let
	     binding that shadows the global unboundness of the var.  */
	  volatile struct specbinding *pdl = specpdl_ptr;
	  while (--pdl >= specpdl)
	    {
	      if (EQ (pdl->symbol, sym) && !pdl->func
		  && EQ (pdl->old_value, Qunbound))
		{
		  message_with_string ("Warning: defvar ignored because %s is let-bound",
				       SYMBOL_NAME (sym), 1);
		  break;
		}
	    }
	}

Since `defcustom' seems to be purely Emacs Lisp, and I don't think this
data is available on the Emacs Lisp level (am I wrong?), perhaps just
creating a C-level function `symbol-let-bound-p' (or something) would
allow us to issue the warning, as a first step?
        
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