* emacs-lisp/byte-run.el (advertised-signature-table): New var.

(set-advertised-calling-convention): New function.
(make-obsolete, define-obsolete-function-alias)
(make-obsolete-variable, define-obsolete-variable-alias):
Make the optional-ness of `when' obsolete.
(define-obsolete-face-alias): Make `when' non-optional.
* help-fns.el (help-function-arglist):
* emacs-lisp/bytecomp.el (byte-compile-fdefinition):
Use advertised-signature-table.

lisp/emacs-lisp/byte-run.el

@@ -106,6 +106,15 @@ The return value of this function is not used."
      (eval-and-compile
        (put ',name 'byte-optimizer 'byte-compile-inline-expand))))
 
+(defvar advertised-signature-table (make-hash-table :test 'eq :weakness 'key))
+
+(defun set-advertised-calling-convention (function signature)
+  "Set the advertised SIGNATURE of FUNCTION.
+This will allow the byte-compiler to warn the programmer when she uses
+an obsolete calling convention."
+  (puthash (indirect-function function) signature
+           advertised-signature-table))
+
 (defun make-obsolete (obsolete-name current-name &optional when)
   "Make the byte-compiler warn that OBSOLETE-NAME is obsolete.
 The warning will say that CURRENT-NAME should be used instead.
@@ -120,6 +129,9 @@ was first made obsolete, for example a date or a release number."
       (put obsolete-name 'byte-compile 'byte-compile-obsolete))
     (put obsolete-name 'byte-obsolete-info (list current-name handler when)))
   obsolete-name)
+(set-advertised-calling-convention
+ ;; New code should always provide the `when' argument.
+ 'make-obsolete '(obsolete-name current-name when))
 
 (defmacro define-obsolete-function-alias (obsolete-name current-name
 						   &optional when docstring)
@@ -137,6 +149,10 @@ See the docstrings of `defalias' and `make-obsolete' for more details."
   `(progn
      (defalias ,obsolete-name ,current-name ,docstring)
      (make-obsolete ,obsolete-name ,current-name ,when)))
+(set-advertised-calling-convention
+ ;; New code should always provide the `when' argument.
+ 'define-obsolete-function-alias
+ '(obsolete-name current-name when &optional docstring))
 
 (defun make-obsolete-variable (obsolete-name current-name &optional when)
   "Make the byte-compiler warn that OBSOLETE-NAME is obsolete.
@@ -152,6 +168,9 @@ was first made obsolete, for example a date or a release number."
     (car (read-from-string (read-string "Obsoletion replacement: ")))))
   (put obsolete-name 'byte-obsolete-variable (cons current-name when))
   obsolete-name)
+(set-advertised-calling-convention
+ ;; New code should always provide the `when' argument.
+ 'make-obsolete-variable '(obsolete-name current-name when))
 
 (defmacro define-obsolete-variable-alias (obsolete-name current-name
 						 &optional when docstring)
@@ -179,14 +198,17 @@ Info node `(elisp)Variable Aliases' for more details."
   `(progn
      (defvaralias ,obsolete-name ,current-name ,docstring)
      (make-obsolete-variable ,obsolete-name ,current-name ,when)))
+(set-advertised-calling-convention
+ ;; New code should always provide the `when' argument.
+ 'define-obsolete-variable-alias
+ '(obsolete-name current-name when &optional docstring))
 
 ;; FIXME This is only defined in this file because the variable- and
 ;; function- versions are too.  Unlike those two, this one is not used
 ;; by the byte-compiler (would be nice if it could warn about obsolete
 ;; faces, but it doesn't really do anything special with faces).
 ;; It only really affects M-x describe-face output.
-(defmacro define-obsolete-face-alias (obsolete-face current-face
-						    &optional when)
+(defmacro define-obsolete-face-alias (obsolete-face current-face when)
   "Make OBSOLETE-FACE a face alias for CURRENT-FACE and mark it obsolete.
 The optional string WHEN gives the Emacs version where OBSOLETE-FACE
 became obsolete."

lisp/emacs-lisp/bytecomp.el

@@ -1230,11 +1230,11 @@ Each function's symbol gets added to `byte-compile-noruntime-functions'."
 
 ;;; sanity-checking arglists
 
-;; If a function has an entry saying (FUNCTION . t).
-;; that means we know it is defined but we don't know how.
-;; If a function has an entry saying (FUNCTION . nil),
-;; that means treat it as not defined.
 (defun byte-compile-fdefinition (name macro-p)
+  ;; If a function has an entry saying (FUNCTION . t).
+  ;; that means we know it is defined but we don't know how.
+  ;; If a function has an entry saying (FUNCTION . nil),
+  ;; that means treat it as not defined.
   (let* ((list (if macro-p
 		   byte-compile-macro-environment
 		 byte-compile-function-environment))
@@ -1248,16 +1248,18 @@ Each function's symbol gets added to `byte-compile-noruntime-functions'."
 			  (and (not macro-p)
 			       (byte-code-function-p (symbol-function fn)))))
 	    (setq fn (symbol-function fn)))
-	  (if (and (not macro-p) (byte-code-function-p fn))
-	      fn
-	    (and (consp fn)
-		 (if (eq 'macro (car fn))
-		     (cdr fn)
-		   (if macro-p
-		       nil
-		     (if (eq 'autoload (car fn))
-			 nil
-		       fn)))))))))
+          (let ((advertised (gethash fn advertised-signature-table t)))
+            (cond
+             ((listp advertised)
+              (if macro-p
+                  `(macro lambda ,advertised)
+                `(lambda ,advertised)))
+             ((and (not macro-p) (byte-code-function-p fn)) fn)
+             ((not (consp fn)) nil)
+             ((eq 'macro (car fn)) (cdr fn))
+             (macro-p nil)
+             ((eq 'autoload (car fn)) nil)
+             (t fn)))))))
 
 (defun byte-compile-arglist-signature (arglist)
   (let ((args 0)