Re: Warning: `mapcar' called for effect; use `mapc' or `dolist'

[Richard Stallman]

    In Common-Lisp, I think you use (declare (special VAR ...)) to indicate
    a localized use of dynamic binding (as the first thing inside the let
    form where it is bound).

    Since Elisp already uses `declare' for some other things, it would seem
    reasonable to also use it to inform the byte compiler that an apparently
    local variable is known to be accessed non-locally.

I would not mind adding this feature to Emacs Lisp.
But I still think that part of Gnus should get a total rewrite
using a different mechanism.