Since Emacs 25, docstrings can be constructed using
(:documentation FORM) in closures, when lexical-binding is on. This
isn't documented except in NEWS. Bug #24773 is about Edebug specs
which have not been updated to recognize :documentation. I'd like to
fix it, so I started trying to figure out which macros accept
:documentation forms so I would know which Edebug specs to update, and
that effort turned into a collection of tests for the feature, see
attached: