bug#16868: Instrumenting macro for edebug turns it "not documented"

[Juanma Barranquero]

Package: emacs
Severity: minor

Is there any reason that instrumenting a macro for edebug "loses" its
docstring, which does not happen for functions?

emacs -Q
eval the following code:

(defmacro test-macro (&rest body)
  "This is a test macro."
  `(progn ,@body))

C-h f test-macro <RET> => This is a test macro
C-u C-M-x
C-h f test-macro <RET> => Not documented.

I can see that it is nothing new, it already happens in 21.X. But it's puzzling.