Edebug: Overload `edebug-form-spec` even less

The `edebug-form-spec` symbol property was used both to map forms's
head symbol to the corresponding spec, and to map spec element names
to their expansion.

This lead to name conflicts which break instrumentation of examples such as

    (cl-flet ((gate (x) x)) (gate 4))

because of the Edebug spec element `gate`.
So introduce a new symbol property `edebug-elem-spec`.

* lisp/subr.el (def-edebug-elem-spec): New function.

* lisp/emacs-lisp/edebug.el (edebug--get-elem-spec): New function.
(edebug-match-symbol): Use it.
(Core Edebug elems): Put them on `edebug-elem-spec` instead of
`edebug-form-spec`.
(ELisp special forms): Set their `edebug-form-spec` via dolist.
(Other non-core Edebug elems): Use `def-edebug-elem-spec`.
(edebug-\`): Use `declare`.

* lisp/emacs-lisp/pcase.el (pcase-PAT, pcase-FUN, pcase-QPAT):
* lisp/skeleton.el (skeleton-edebug-spec):
* lisp/emacs-lisp/cl-macs.el: Use `def-edebug-elem-spec`.

* test/lisp/emacs-lisp/edebug-tests.el
(edebug-tests--conflicting-internal-names): New test.
* test/lisp/emacs-lisp/edebug-resources/edebug-test-code.el
(edebug-test-code-cl-flet1): New test case.

* doc/lispref/edebug.texi (Specification List): Add `def-edebug-elem-spec`.
(Specification Examples): Use it.

* doc/lispref/loading.texi (Hooks for Loading): Avoid the use of
`def-edebug-spec` in example (better use `debug` declaration).

1 files changed, 16 insertions, 1 deletions

diff --git a/lisp/subr.el b/lisp/subr.el
index 454ea54b6a4..70ee281fe6e 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -82,7 +82,7 @@ Testcover will raise an error."
   form)
 
 (defmacro def-edebug-spec (symbol spec)
-  "Set the `edebug-form-spec' property of SYMBOL according to SPEC.
+  "Set the Edebug SPEC to use for sexps which have SYMBOL as head.
 Both SYMBOL and SPEC are unevaluated.  The SPEC can be:
 0 (instrument no arguments); t (instrument all arguments);
 a symbol (naming a function with an Edebug specification); or a list.
@@ -91,6 +91,21 @@ Info node `(elisp)Specification List' for details."
   (declare (indent 1))
   `(put (quote ,symbol) 'edebug-form-spec (quote ,spec)))
 
+(defun def-edebug-elem-spec (name spec)
+  "Define a new Edebug spec element NAME as shorthand for SPEC.
+The SPEC has to be a list or a symbol.
+The elements of the list describe the argument types; see
+Info node `(elisp)Specification List' for details.
+If SPEC is a symbol it should name another pre-existing Edebug element."
+  (declare (indent 1))
+  (when (string-match "\\`[&:]" (symbol-name name))
+    ;; & and : have special meaning in spec element names.
+    (error "Edebug spec name cannot start with '&' or ':'"))
+  (unless (consp spec)
+    (error "Edebug spec has to be a list: %S" spec))
+  (put name 'edebug-elem-spec spec))
+
+
 (defmacro lambda (&rest cdr)
   "Return an anonymous function.
 Under dynamic binding, a call of the form (lambda ARGS DOCSTRING