Re: Adding rassq-delete-all to lisp/subr.el.

[Richard Stallman]

    > Strange, (cadr ...) is just a defsubst for (car (cdr ...)).  So
    > compiled it should make no difference.

    The defsubst binds and unbinds x.  I consider that a byte compiler
    deficiency.

In general, the byte compiler cannot omit that binding.
It does not know that the binding won't be  referred to
from one of the functions that is called.

However, in this specific case, cadr calls only primitives, so that
can't happen.  It would not be too hard to change the compiler to
recognize that and eliminate the binding.  That could be a useful
thing to work on, but shouldn't be installed now.