Catch function objects embedded in code

[MichaelBlume]

It's not that hard when writing a macro to accidentally wind up generating code that has an actual function object where there should be an s-expression. Badly contrived example:

(defmacro add2 [x]
  `(~+ ~x 2))

This will work even though the author probably should have written

(defmacro add2 [x]
  `(+ ~x 2))

It'd be nice to have a clear warning about this.