Introduce element &error into edebug specification lists for macros

This fixes bug #37540.

* lisp/emacs-lisp/edebug.el (top level): New entry for &error in alist used to
associate elements with their handling functions.
(edebug-match-&error): New function.
(nested-backquote-form): Use the new element &error to abort instrumentation
on encountering a three deep nesting of backquotes (without intervening
commas).

* doc/lispref/edebug.texi (Specification List): Add an entry for &error.

* etc/NEWS: Add an entry for &error.

1 files changed, 5 insertions, 0 deletions

diff --git a/doc/lispref/edebug.texi b/doc/lispref/edebug.texi
index 8be8307c75f..cfef5c12d1e 100644
--- a/doc/lispref/edebug.texi
+++ b/doc/lispref/edebug.texi
@@ -1362,6 +1362,11 @@ while matching the remainder of the specifications at this level.  This
 is primarily used to generate more specific syntax error messages.  See
 @ref{Backtracking}, for more details.  Also see the @code{let} example.
 
+@item &error
+@code{&error} should be followed by a string, an error message, in the
+edebug-spec; it aborts the instrumentation, displaying the message in
+the minibuffer.
+
 @item @var{other-symbol}
 @cindex indirect specifications
 Any other symbol in a specification list may be a predicate or an