Bind-fn-annotation
Get the annotation associated with the innermost call of the given function being rewritten
Usage:
(bind-fn-annotation free-var 'my-fn)
finds the record of the innermost call of my-fn in the FGL rewriter's
stack, and checks whether there was a call of annotate wrapped
immediately around it. If so, it binds the given free variable to the first
argument of that call of annotate; otherwise, it binds it to NIL. The
bind-fn-annotation form always returns T, so it can be used as a
hypothesis in a rewrite rule.
A related utility is bind-nth-fn-annotation which gets the annotation
associated with the nth-innermost call of the function, rather than the
innermost.
