Allow setting font-lock-keyword property using declare form

* doc/lispref/functions.texi (Declare Form): Document
'font-lock-keyword' meta property.
* etc/NEWS: Announce addition of 'font-lock-keyword' meta property.
* lisp/emacs-lisp/byte-run.el (byte-run--set-font-lock-keyword): New
function.
* (defun-declarations-alist): Add entry for 'font-lock-keyword', using
'byte-run--set-font-lock-keyword'.
* (with-no-warnings): Set 'font-lock-keyword' meta property.

doc/lispref/functions.texi

@@ -2924,6 +2924,11 @@ original signature to avoid these issues.
 This is valid for macros only.  Macros with this declaration are
 highlighted by font-lock (@pxref{Font Lock Mode}) as normal functions,
 not specially as macros.
+
+@item font-lock-keyword
+Normal functions with this declaration are highlighted by font-lock
+(@pxref{Font Lock Mode}) like macros.
+
 @end table
 
 @end defmac

etc/NEWS

@@ -467,6 +467,7 @@ Emacs 30.  It allows Lisp programs that present completion candidates
 ("completion frontends") to provide additional information which can be
 used to adjust or optimize completion candidates computation.
 
++++
 ** D-Bus
 
 +++
@@ -508,6 +509,13 @@ the actual and expected output.
 Strings should use numeric abbreviations like "-0600" instead of
 alphabetic abbreviations like "CST", which are too often ambiguous.
 
+** Function 'declare' forms
+
++++
+*** New 'font-lock-keyword' function declaration
+The declaration '(font-lock-keyword t)' specifies that a normal
+functions is to be highlighted by font-lock a macros.
+
 
 * Changes in Emacs 32.1 on Non-Free Operating Systems
 

lisp/emacs-lisp/byte-run.el

@@ -252,6 +252,11 @@ declaration" f2 f))
           (let ((code (apply fn args)))
             (list 'progn ':autoload-end code)))))
 
+(defalias 'byte-run--set-font-lock-keyword
+  #'(lambda (name _args val)
+      (list 'function-put (list 'quote name)
+	    ''font-lock-keyword (list 'quote val))))
+
 ;; Add any new entries to info node `(elisp)Declare Form'.
 (defvar defun-declarations-alist
   (list
@@ -276,7 +281,8 @@ If `error-free', drop calls even if `byte-compile-delete-errors' is nil.")
    (list 'completion #'byte-run--set-completion)
    (list 'modes #'byte-run--set-modes)
    (list 'interactive-args #'byte-run--set-interactive-args)
-   (list 'ftype #'byte-run--set-function-type))
+   (list 'ftype #'byte-run--set-function-type)
+   (list 'font-lock-keyword #'byte-run--set-font-lock-keyword))
   "List associating function properties to their macro expansion.
 Each element of the list takes the form (PROP FUN) where FUN is
 a function.  For each (PROP . VALUES) in a function's declaration,
@@ -707,7 +713,7 @@ enabled."
 
 (defun with-no-warnings (&rest body)
   "Like `progn', but prevents compiler warnings in the body."
-  (declare (indent 0))
+  (declare (indent 0) (font-lock-keyword t))
   ;; The implementation for the interpreter is basically trivial.
   (car (last body)))