Help find-function find methods defined inside macros

* doc/lispref/functions.texi (Finding Definitions): Document the
expanded definition-finding extension mechanism.
* etc/NEWS: Briefly describe the new feature.
* lisp/emacs-lisp/cl-generic.el
(cl--generic-find-defgeneric-regexp): Use defconst now that we
no longer have purespace.
(cl--generic-search-method-make-form-matcher): New function.
* lisp/emacs-lisp/find-func.el (find-function-regexp-alist)
(find-function-search-for-symbol): Parse out the new
factory function.
(find-function--search-by-expanding-macros): Try using it when
searching for definitions by expanding macros.

1 files changed, 15 insertions, 3 deletions

diff --git a/doc/lispref/functions.texi b/doc/lispref/functions.texi
index 1279b15b819..83acbff0885 100644
--- a/doc/lispref/functions.texi
+++ b/doc/lispref/functions.texi
@@ -849,9 +849,16 @@ The alist @code{find-function-regexp-alist} associates object types with
 a regexp or function that finds the definition of that object in its
 source file.  Each element's car is a symbol the describes the type of
 object, or @code{nil} to identify functions defined with @code{defun}.
-Each element's cdr is a symbol: either the value of that symbol is a
-string interpreted as a regexp, or that symbol names a function that can
-find the definition.
+Each element's cdr can be:
+
+@itemize
+@item
+A symbol whose value is a string interpreted as a regexp
+@item
+A symbol naming a function that can find the definition
+@item
+A cons cell where the car is a regexp (or function that returns one) and the cdr is a function that creates a matcher for macroexpanded forms
+@end itemize
 
 A regexp string is actually a format string, and @code{%s} will be
 substituted with the name of the symbol we are looking for.
@@ -859,6 +866,11 @@ substituted with the name of the symbol we are looking for.
 A function will be called with one argument, the (symbol for) the object
 we are searching for.
 
+The form-matcher function in a cons cell value is called with one argument (the
+symbol being sought) and should return a function that takes a form and returns
+non-nil if the form defines the sought symbol. This is useful for finding
+definitions that are created by macro expansion.
+
 @cindex @code{definition-name} (symbol property)
 If the function to be found is defined by a macro, it may be hard for
 Emacs to find the definition site in the source code.  A macro call may