Andrea Corallo <acorallo@gnu.org> writes:

> branch: master
> commit da8b06bd6181bc56fb0f133d17cae7eff44a83e8
> Merge: 2f5c9b31161 64d3100cb59
> Author: Andrea Corallo <acorallo@gnu.org>
> Commit: Andrea Corallo <acorallo@gnu.org>
>
>     Merge branch 'lisp-func-type-decls' into 'master'
> ---
>  doc/lispref/functions.texi     | 52 ++++++++++++++++++++++++++++++++++
>  etc/NEWS                       |  5 ++++
>  lisp/custom.el                 |  3 +-
>  lisp/emacs-lisp/byte-run.el    |  8 +++++-
>  lisp/emacs-lisp/comp-common.el | 64 +++++++++++++-----------------------------
>  lisp/emacs-lisp/comp.el        | 24 +++++++++++-----
>  lisp/emacs-lisp/lisp.el        |  3 +-
>  lisp/emacs-lisp/regexp-opt.el  |  3 +-
>  lisp/env.el                    |  3 +-
>  lisp/files.el                  |  1 +
>  lisp/help-fns.el               |  2 +-
>  lisp/simple.el                 | 10 +++++--
>  lisp/subr.el                   | 36 ++++++++++++++++--------
>  lisp/window.el                 |  9 ++++--
>  14 files changed, 147 insertions(+), 76 deletions(-)
>
> diff --git a/doc/lispref/functions.texi b/doc/lispref/functions.texi
> index c57de08460f..d88f5d05339 100644
> --- a/doc/lispref/functions.texi
> +++ b/doc/lispref/functions.texi
> @@ -2709,6 +2709,58 @@ native code emitted for the function.  In particular, if @var{n} is
>  @minus{}1, native compilation of the function will emit bytecode
>  instead of native code for the function.
>  
> +@item (type @var{type})
> +Declare @var{type} to be the type of this function.  This is used for
> +documentation by @code{describe-function}.  Also it can be used by the
> +native compiler (@pxref{Native Compilation}) for improving code
> +generation and for deriving more precisely the type of other functions
> +without type declaration.
> +
> +@var{type} is a type specifier in the form @w{@code{(function
> +(ARG-1-TYPE ... ARG-N-TYPE) RETURN-TYPE)}}.  Argument types can be
> +interleaved with symbols @code{&optional} and @code{&rest} to match the
> +function's arguments (@pxref{Argument List}).
> +
> +Here's an example of using @code{type} inside @code{declare} to declare
> +a function @code{positive-p} that takes an argument of type @var{number}
> +and return a @var{boolean}:
> +
> +@group
> +@lisp
> +(defun positive-p (x)
> +  (declare (type (function (number) boolean)))
> +  (when (> x 0)
> +    t))
> +@end lisp
> +@end group
> +
> +Similarly this declares a function @code{cons-or-number} that: expects a
> +first argument being a @var{cons} or a @var{number}, a second optional
> +argument of type @var{string} and return one of the symbols
> +@code{is-cons} or @code{is-number}:
> +
> +@group
> +@lisp
> +(defun cons-or-number (x &optional err-msg)
> +  (declare (type (function ((or cons number) &optional string)
> +			   (member is-cons is-number))))
> +  (if (consp x)
> +      'is-cons
> +    (if (numberp x)
> +	'is-number
> +      (error (or err-msg "Unexpected input")))))
> +@end lisp
> +@end group
> +
> +More types are described in the Lisp Data Types chapter (@ref{Lisp Data
> +Types}).
> +
> +Declaring a function with an incorrect type produces undefined behavior
> +and could lead to unexpected results or might even crash Emacs when code
> +is native-compiled and loaded.  Note also that when redefining (or
> +advising) a type declared function the replacement should respect the
> +original signature to avoid undefined behavior.
> +
>  @item no-font-lock-keyword
>  This is valid for macros only.  Macros with this declaration are
>  highlighted by font-lock (@pxref{Font Lock Mode}) as normal functions,
> diff --git a/etc/NEWS b/etc/NEWS
> index 4d363d300a8..8477a1eed58 100644
> --- a/etc/NEWS
> +++ b/etc/NEWS
> @@ -1939,6 +1939,11 @@ unibyte string.
>  
>  * Lisp Changes in Emacs 30.1
>  
> ++++
> +** Function type declaration
> +It is now possible, using the 'declare' macro, to declare expected types
> +of function arguments and return type.
> +
>  ** New types 'closure' and 'interpreted-function'.
>  'interpreted-function' is the new type used for interpreted functions,
>  and 'closure' is the common parent type of 'interpreted-function'
> diff --git a/lisp/custom.el b/lisp/custom.el
> index a19b14aaf8a..6f2aa18ba1d 100644
> --- a/lisp/custom.el
> +++ b/lisp/custom.el
> @@ -667,7 +667,8 @@ If NOSET is non-nil, don't bother autoloading LOAD when setting the variable."
>  A customizable variable is either (i) a variable whose property
>  list contains a non-nil `standard-value' or `custom-autoload'
>  property, or (ii) an alias for another customizable variable."
> -  (declare (side-effect-free t))
> +  (declare (type (function (symbol) t))
> +           (side-effect-free t))
>    (when (symbolp variable)
>      (setq variable (indirect-variable variable))
>      (or (get variable 'standard-value)
> diff --git a/lisp/emacs-lisp/byte-run.el b/lisp/emacs-lisp/byte-run.el
> index cc176821026..84cc83f2270 100644
> --- a/lisp/emacs-lisp/byte-run.el
> +++ b/lisp/emacs-lisp/byte-run.el
> @@ -217,6 +217,11 @@ So far, FUNCTION can only be a symbol, not a lambda expression."
>                   (cadr elem)))
>                val)))))
>  
> +(defalias 'byte-run--set-function-type
> +  #'(lambda (f _args &rest val)
> +      (list 'function-put (list 'quote f)
> +            ''function-type (list 'quote val))))
> +
>  ;; Add any new entries to info node `(elisp)Declare Form'.
>  (defvar defun-declarations-alist
>    (list
> @@ -239,7 +244,8 @@ If `error-free', drop calls even if `byte-compile-delete-errors' is nil.")
>     (list 'speed #'byte-run--set-speed)
>     (list 'completion #'byte-run--set-completion)
>     (list 'modes #'byte-run--set-modes)
> -   (list 'interactive-args #'byte-run--set-interactive-args))
> +   (list 'interactive-args #'byte-run--set-interactive-args)
> +   (list 'type #'byte-run--set-function-type))
>    "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,
> diff --git a/lisp/emacs-lisp/comp-common.el b/lisp/emacs-lisp/comp-common.el
> index 62fd28f772e..ef40882a98a 100644
> --- a/lisp/emacs-lisp/comp-common.el
> +++ b/lisp/emacs-lisp/comp-common.el
> @@ -68,7 +68,7 @@ Used to modify the compiler environment."
>    :risky t
>    :version "28.1")
>  
> -(defconst comp-known-type-specifiers
> +(defconst comp-primitive-type-specifiers
>    `(
>      ;; Functions we can trust not to be redefined, or, if redefined,
>      ;; to expose the same type.  The vast majority of these are
> @@ -97,7 +97,6 @@ Used to modify the compiler environment."
>      (assq (function (t list) list))
>      (atan (function (number &optional number) float))
>      (atom (function (t) boolean))
> -    (bignump (function (t) boolean))
>      (bobp (function () boolean))
>      (bolp (function () boolean))
>      (bool-vector-count-consecutive
> @@ -107,7 +106,6 @@ Used to modify the compiler environment."
>      (bool-vector-p (function (t) boolean))
>      (bool-vector-subsetp (function (bool-vector bool-vector) boolean))
>      (boundp (function (symbol) boolean))
> -    (buffer-end (function ((or number marker)) integer))
>      (buffer-file-name (function (&optional buffer) (or string null)))
>      (buffer-list (function (&optional frame) list))
>      (buffer-local-variables (function (&optional buffer) list))
> @@ -157,8 +155,6 @@ Used to modify the compiler environment."
>      (copy-sequence (function (sequence) sequence))
>      (copysign (function (float float) float))
>      (cos (function (number) float))
> -    (count-lines
> -     (function ((or integer marker) (or integer marker) &optional t) integer))
>      (current-buffer (function () buffer))
>      (current-global-map (function () cons))
>      (current-indentation (function () integer))
> @@ -171,7 +167,6 @@ Used to modify the compiler environment."
>      (current-time-zone (function (&optional (or number list)
>                                              (or symbol string cons integer))
>                                   cons))
> -    (custom-variable-p (function (symbol) t))
>      (decode-char (function (cons t) (or fixnum null)))
>      (decode-time (function (&optional (or number list)
>                                        (or symbol string cons integer)
> @@ -179,7 +174,6 @@ Used to modify the compiler environment."
>                             cons))
>      (default-boundp (function (symbol) boolean))
>      (default-value (function (symbol) t))
> -    (degrees-to-radians (function (number) float))
>      (documentation
>       (function ((or function symbol subr) &optional t) (or null string)))
>      (downcase (function ((or fixnum string)) (or fixnum string)))
> @@ -192,7 +186,6 @@ Used to modify the compiler environment."
>      (eql (function (t t) boolean))
>      (equal (function (t t) boolean))
>      (error-message-string (function (list) string))
> -    (eventp (function (t) boolean))
>      (exp (function (number) float))
>      (expt (function (number number) number))
>      (fboundp (function (symbol) boolean))
> @@ -207,7 +200,6 @@ Used to modify the compiler environment."
>      (file-readable-p (function (string) boolean))
>      (file-symlink-p (function (string) (or boolean string)))
>      (file-writable-p (function (string) boolean))
> -    (fixnump (function (t) boolean))
>      (float (function (number) float))
>      (float-time (function (&optional (or number list)) float))
>      (floatp (function (t) boolean))
> @@ -230,18 +222,12 @@ Used to modify the compiler environment."
>       (function (&optional (or buffer string) (or symbol (integer 0 0)))
>                 (or null window)))
>      (get-file-buffer (function (string) (or null buffer)))
> -    (get-largest-window (function (&optional t t t) (or window null)))
> -    (get-lru-window (function (&optional t t t) (or window null)))
> -    (getenv (function (string &optional frame) (or null string)))
>      (gethash (function (t hash-table &optional t) t))
>      (hash-table-count (function (hash-table) integer))
>      (hash-table-p (function (t) boolean))
>      (identity (function (t) t))
> -    (ignore (function (&rest t) null))
> -    (int-to-string (function (number) string))
>      (integer-or-marker-p (function (t) boolean))
>      (integerp (function (t) boolean))
> -    (interactive-p (function () boolean))
>      (intern-soft (function ((or string symbol) &optional (or obarray vector))
>                             symbol))
>      (invocation-directory (function () string))
> @@ -250,8 +236,6 @@ Used to modify the compiler environment."
>      (keymap-parent (function (cons) (or cons null)))
>      (keymapp (function (t) boolean))
>      (keywordp (function (t) boolean))
> -    (last (function (list &optional integer) list))
> -    (lax-plist-get (function (list t) t))
>      (ldexp (function (number integer) float))
>      (length (function (t) (integer 0 *)))
>      (length< (function (sequence fixnum) boolean))
> @@ -265,7 +249,6 @@ Used to modify the compiler environment."
>      (local-variable-p (function (symbol &optional buffer) boolean))
>      (locale-info (function ((member codeset days months paper)) (or null string)))
>      (log (function (number number) float))
> -    (log10 (function (number) float))
>      (logand (function (&rest (or integer marker)) integer))
>      (logb (function (number) integer))
>      (logcount (function (integer) integer))
> @@ -273,7 +256,6 @@ Used to modify the compiler environment."
>      (lognot (function (integer) integer))
>      (logxor (function (&rest (or integer marker)) integer))
>      ;; (lsh (function ((integer ,most-negative-fixnum *) integer) integer)) ?
> -    (lsh (function (integer integer) integer))
>      (make-byte-code
>       (function ((or fixnum list) string vector integer &optional string t
>                  &rest t)
> @@ -282,14 +264,12 @@ Used to modify the compiler environment."
>      (make-marker (function () marker))
>      (make-string (function (integer fixnum &optional t) string))
>      (make-symbol (function (string) symbol))
> -    (mark (function (&optional t) (or integer null)))
>      (mark-marker (function () marker))
>      (marker-buffer (function (marker) (or buffer null)))
>      (markerp (function (t) boolean))
>      (max (function ((or number marker) &rest (or number marker)) number))
>      (max-char (function (&optional t) fixnum))
>      (member (function (t list) list))
> -    (memory-limit (function () integer))
>      (memq (function (t list) list))
>      (memql (function (t list) list))
>      (min (function ((or number marker) &rest (or number marker)) number))
> @@ -298,7 +278,6 @@ Used to modify the compiler environment."
>      (mod
>       (function ((or number marker) (or number marker))
>                 (or (integer 0 *) (float 0 *))))
> -    (mouse-movement-p (function (t) boolean))
>      (multibyte-char-to-unibyte (function (fixnum) fixnum))
>      (natnump (function (t) boolean))
>      (next-window (function (&optional window t t) window))
> @@ -310,9 +289,7 @@ Used to modify the compiler environment."
>      (number-or-marker-p (function (t) boolean))
>      (number-to-string (function (number) string))
>      (numberp (function (t) boolean))
> -    (one-window-p (function (&optional t t) boolean))
>      (overlayp (function (t) boolean))
> -    (parse-colon-path (function (string) list))
>      (plist-get (function (list t &optional t) t))
>      (plist-member (function (list t &optional t) list))
>      (point (function () integer))
> @@ -325,13 +302,11 @@ Used to modify the compiler environment."
>      (processp (function (t) boolean))
>      (proper-list-p (function (t) (or fixnum null)))
>      (propertize (function (string &rest t) string))
> -    (radians-to-degrees (function (number) float))
>      (rassoc (function (t list) list))
>      (rassq (function (t list) list))
>      (read-from-string (function (string &optional integer integer) cons))
>      (recent-keys (function (&optional (or cons null)) vector))
>      (recursion-depth (function () integer))
> -    (regexp-opt (function (list) string))
>      (regexp-quote (function (string) string))
>      (region-beginning (function () integer))
>      (region-end (function () integer))
> @@ -387,7 +362,6 @@ Used to modify the compiler environment."
>      (upcase (function ((or fixnum string)) (or fixnum string)))
>      (user-full-name (function (&optional integer) (or string null)))
>      (user-login-name (function (&optional integer) (or string null)))
> -    (user-original-login-name (function (&optional integer) (or string null)))
>      (user-real-login-name (function () string))
>      (user-real-uid (function () integer))
>      (user-uid (function () integer))
> @@ -400,13 +374,8 @@ Used to modify the compiler environment."
>      (window-live-p (function (t) boolean))
>      (window-valid-p (function (t) boolean))
>      (windowp (function (t) boolean))
> -    (zerop (function (number) boolean))
> -    ;; Type hints
> -    (comp-hint-fixnum (function (t) fixnum))
> -    (comp-hint-cons (function (t) cons))
>      ;; Non returning functions
>      (throw (function (t t) nil))
> -    (error (function (string &rest t) nil))
>      (signal (function (symbol t) nil)))
>    "Alist used for type propagation.")
>  
> @@ -532,22 +501,27 @@ Account for `native-comp-eln-load-path' and `comp-native-version-dir'."
>  (defun comp-function-type-spec (function)
>    "Return the type specifier of FUNCTION.
>  
> -This function returns a cons cell whose car is the function
> -specifier, and cdr is a symbol, either `inferred' or `know'.
> -If the symbol is `inferred', the type specifier is automatically
> -inferred from the code itself by the native compiler; if it is
> -`know', the type specifier comes from `comp-known-type-specifiers'."
> -  (let ((kind 'know)
> -        type-spec )
> -    (when-let ((res (assoc function comp-known-type-specifiers)))
> +This function returns a cons cell whose car is the function specifier,
> +and cdr is a symbol, either `inferred' or `declared'.  If the symbol is
> +`inferred', the type specifier is automatically inferred from the code
> +itself by the native compiler; if it is `declared', the type specifier
> +comes from `comp-primitive-type-specifiers' or the function type declaration
> +itself."
> +  (let ((kind 'declared)
> +        type-spec)
> +    (when-let ((res (assoc function comp-primitive-type-specifiers)))
> +      ;; Declared primitive
>        (setf type-spec (cadr res)))
>      (let ((f (and (symbolp function)
>                    (symbol-function function))))
> -      (when (and f
> -                 (null type-spec)
> -                 (subr-native-elisp-p f))
> -        (setf kind 'inferred
> -              type-spec (subr-type f))))
> +      (when (and f (null type-spec))
> +        (if-let ((delc-type (function-get function 'function-type)))
> +            ;; Declared Lisp function
> +            (setf type-spec (car delc-type))
> +          (when (subr-native-elisp-p f)
> +            ;; Native compiled inferred
> +            (setf kind 'inferred
> +                  type-spec (subr-type f))))))
>      (when type-spec
>          (cons type-spec kind))))
>  
> diff --git a/lisp/emacs-lisp/comp.el b/lisp/emacs-lisp/comp.el
> index 2ec55ed98ee..d7cd6b79c86 100644
> --- a/lisp/emacs-lisp/comp.el
> +++ b/lisp/emacs-lisp/comp.el
> @@ -179,16 +179,24 @@ For internal use by the test suite only.")
>  Each function in FUNCTIONS is run after PASS.
>  Useful to hook into pass checkers.")
>  
> -(defconst comp-known-func-cstr-h
> +(defconst comp-primitive-func-cstr-h
>    (cl-loop
>     with comp-ctxt = (make-comp-cstr-ctxt)
>     with h = (make-hash-table :test #'eq)
> -   for (f type-spec) in comp-known-type-specifiers
> +   for (f type-spec) in comp-primitive-type-specifiers
>     for cstr = (comp-type-spec-to-cstr type-spec)
>     do (puthash f cstr h)
>     finally return h)
>    "Hash table function -> `comp-constraint'.")
>  
> +(defun comp--get-function-cstr (function)
> +  "Given FUNCTION return the corresponding `comp-constraint'."
> +  (when (symbolp function)
> +    (let ((f (symbol-function function)))
> +      (or (gethash f comp-primitive-func-cstr-h)
> +          (when-let ((res (function-get function 'function-type)))
> +            (comp-type-spec-to-cstr (car res)))))))
> +
>  ;; Keep it in sync with the `cl-deftype-satisfies' property set in
>  ;; cl-macs.el. We can't use `cl-deftype-satisfies' directly as the
>  ;; relation type <-> predicate is not bijective (bug#45576).
> @@ -2102,10 +2110,10 @@ TARGET-BB-SYM is the symbol name of the target block."
>       (when-let ((match
>                   (pcase insn
>                     (`(set ,lhs (,(pred comp--call-op-p) ,f . ,args))
> -                    (when-let ((cstr-f (gethash f comp-known-func-cstr-h)))
> +                    (when-let ((cstr-f (comp--get-function-cstr f)))
>                        (cl-values f cstr-f lhs args)))
>                     (`(,(pred comp--call-op-p) ,f . ,args)
> -                    (when-let ((cstr-f (gethash f comp-known-func-cstr-h)))
> +                    (when-let ((cstr-f (comp--get-function-cstr f)))
>                        (cl-values f cstr-f nil args))))))
>         (cl-multiple-value-bind (f cstr-f lhs args) match
>           (cl-loop
> @@ -2642,7 +2650,7 @@ Fold the call in case."
>                 (comp-cstr-imm-vld-p (car args)))
>        (setf f (comp-cstr-imm (car args))
>              args (cdr args)))
> -    (when-let ((cstr-f (gethash f comp-known-func-cstr-h)))
> +    (when-let ((cstr-f (comp--get-function-cstr f)))
>        (let ((cstr (comp-cstr-f-ret cstr-f)))
>          (when (comp-cstr-empty-p cstr)
>            ;; Store it to be rewritten as non local exit.
> @@ -3301,11 +3309,13 @@ Prepare every function for final compilation and drive the C back-end."
>  ;; are assumed just to be true. Use with extreme caution...
>  
>  (defun comp-hint-fixnum (x)
> -  (declare (gv-setter (lambda (val) `(setf ,x ,val))))
> +  (declare (type (function (t) fixnum))
> +           (gv-setter (lambda (val) `(setf ,x ,val))))
>    x)
>  
>  (defun comp-hint-cons (x)
> -  (declare (gv-setter (lambda (val) `(setf ,x ,val))))
> +  (declare (type (function (t) cons))
> +           (gv-setter (lambda (val) `(setf ,x ,val))))
>    x)
>  
>  
> diff --git a/lisp/emacs-lisp/lisp.el b/lisp/emacs-lisp/lisp.el
> index 7e6db51b1d5..9edc11ad132 100644
> --- a/lisp/emacs-lisp/lisp.el
> +++ b/lisp/emacs-lisp/lisp.el
> @@ -534,7 +534,8 @@ major mode's decisions about context.")
>    "Return the \"far end\" position of the buffer, in direction ARG.
>  If ARG is positive, that's the end of the buffer.
>  Otherwise, that's the beginning of the buffer."
> -  (declare (side-effect-free error-free))
> +  (declare (type (function ((or number marker)) integer))
> +           (side-effect-free error-free))
>    (if (> arg 0) (point-max) (point-min)))
>  
>  (defun end-of-defun (&optional arg interactive)
> diff --git a/lisp/emacs-lisp/regexp-opt.el b/lisp/emacs-lisp/regexp-opt.el
> index 59c1b7d8e10..f23343a34c6 100644
> --- a/lisp/emacs-lisp/regexp-opt.el
> +++ b/lisp/emacs-lisp/regexp-opt.el
> @@ -130,7 +130,8 @@ usually more efficient than that of a simplified version:
>       (concat (car parens)
>               (mapconcat \\='regexp-quote strings \"\\\\|\")
>               (cdr parens))))"
> -  (declare (pure t) (side-effect-free t))
> +  (declare (type (function (list &optional t) string))
> +           (pure t) (side-effect-free t))
>    (save-match-data
>      ;; Recurse on the sorted list.
>      (let* ((max-lisp-eval-depth 10000)
> diff --git a/lisp/env.el b/lisp/env.el
> index e0a8df8476c..7d0c7dd0126 100644
> --- a/lisp/env.el
> +++ b/lisp/env.el
> @@ -207,7 +207,8 @@ parameter.
>  Otherwise, this function searches `process-environment' for
>  VARIABLE.  If it is not found there, then it continues the search
>  in the environment list of the selected frame."
> -  (declare (side-effect-free t))
> +  (declare (type (function (string &optional frame) (or null string)))
> +           (side-effect-free t))
>    (interactive (list (read-envvar-name "Get environment variable: " t)))
>    (let ((value (getenv-internal (if (multibyte-string-p variable)
>  				    (encode-coding-string
> diff --git a/lisp/files.el b/lisp/files.el
> index b7ebb727c72..c24e48e3db2 100644
> --- a/lisp/files.el
> +++ b/lisp/files.el
> @@ -862,6 +862,7 @@ GNU and Unix systems).  Substitute environment variables into the
>  resulting list of directory names.  For an empty path element (i.e.,
>  a leading or trailing separator, or two adjacent separators), return
>  nil (meaning `default-directory') as the associated list element."
> +  (declare (type (function (string) list)))
>    (when (stringp search-path)
>      (let ((spath (substitute-env-vars search-path))
>            (double-slash-special-p
> diff --git a/lisp/help-fns.el b/lisp/help-fns.el
> index 9bf2f61aee6..182b22549b5 100644
> --- a/lisp/help-fns.el
> +++ b/lisp/help-fns.el
> @@ -732,7 +732,7 @@ the C sources, too."
>                (insert (format
>                         (if (eq kind 'inferred)
>                             "\nInferred type: %s\n"
> -                         "\nType: %s\n")
> +                         "\nDeclared type: %s\n")
>                         type-spec))))
>            (fill-region fill-begin (point))
>            high-doc)))))
> diff --git a/lisp/simple.el b/lisp/simple.el
> index be64f3574e0..a459f6ecfd2 100644
> --- a/lisp/simple.el
> +++ b/lisp/simple.el
> @@ -1762,7 +1762,9 @@ not at the start of a line.
>  
>  When IGNORE-INVISIBLE-LINES is non-nil, invisible lines are not
>  included in the count."
> -  (declare (side-effect-free t))
> +  (declare (type (function ((or integer marker) (or integer marker) &optional t)
> +                           integer))
> +           (side-effect-free t))
>    (save-excursion
>      (save-restriction
>        (narrow-to-region start end)
> @@ -6882,7 +6884,8 @@ is active, and returns an integer or nil in the usual way.
>  
>  If you are using this in an editing command, you are most likely making
>  a mistake; see the documentation of `set-mark'."
> -  (declare (side-effect-free t))
> +  (declare (type (function (&optional t) (or integer null)))
> +           (side-effect-free t))
>    (if (or force (not transient-mark-mode) mark-active mark-even-if-inactive)
>        (marker-position (mark-marker))
>      (signal 'mark-inactive nil)))
> @@ -11163,7 +11166,8 @@ killed."
>  
>  (defun lax-plist-get (plist prop)
>    "Extract a value from a property list, comparing with `equal'."
> -  (declare (pure t) (side-effect-free t) (obsolete plist-get "29.1"))
> +  (declare (type (function (list t) t))
> +           (pure t) (side-effect-free t) (obsolete plist-get "29.1"))
>    (plist-get plist prop #'equal))
>  
>  (defun lax-plist-put (plist prop val)
> diff --git a/lisp/subr.el b/lisp/subr.el
> index 352ecc315ef..92d1e50ab2c 100644
> --- a/lisp/subr.el
> +++ b/lisp/subr.el
> @@ -451,7 +451,8 @@ This function accepts any number of arguments in ARGUMENTS.
>  Also see `always'."
>    ;; Not declared `side-effect-free' because we don't want calls to it
>    ;; elided; see `byte-compile-ignore'.
> -  (declare (pure t) (completion ignore))
> +  (declare (type (function (&rest t) null))
> +           (pure t) (completion ignore))
>    (interactive)
>    nil)
>  
> @@ -480,7 +481,8 @@ for the sake of consistency.
>  
>  To alter the look of the displayed error messages, you can use
>  the `command-error-function' variable."
> -  (declare (advertised-calling-convention (string &rest args) "23.1"))
> +  (declare (type (function (string &rest t) nil))
> +           (advertised-calling-convention (string &rest args) "23.1"))
>    (signal 'error (list (apply #'format-message args))))
>  
>  (defun user-error (format &rest args)
> @@ -545,19 +547,22 @@ was called."
>    "Return t if NUMBER is zero."
>    ;; Used to be in C, but it's pointless since (= 0 n) is faster anyway because
>    ;; = has a byte-code.
> -  (declare (pure t) (side-effect-free t)
> +  (declare (type (function (number) boolean))
> +           (pure t) (side-effect-free t)
>             (compiler-macro (lambda (_) `(= 0 ,number))))
>    (= 0 number))
>  
>  (defun fixnump (object)
>    "Return t if OBJECT is a fixnum."
> -  (declare (side-effect-free error-free))
> +  (declare (type (function (t) boolean))
> +           (side-effect-free error-free))
>    (and (integerp object)
>         (<= most-negative-fixnum object most-positive-fixnum)))
>  
>  (defun bignump (object)
>    "Return t if OBJECT is a bignum."
> -  (declare (side-effect-free error-free))
> +  (declare (type (function (t) boolean))
> +           (side-effect-free error-free))
>    (and (integerp object) (not (fixnump object))))
>  
>  (defun lsh (value count)
> @@ -570,7 +575,8 @@ Most uses of this function turn out to be mistakes.  We recommend
>  to use `ash' instead, unless COUNT could ever be negative, and
>  if, when COUNT is negative, your program really needs the special
>  treatment of negative COUNT provided by this function."
> -  (declare (compiler-macro
> +  (declare (type (function (integer integer) integer))
> +           (compiler-macro
>              (lambda (form)
>                (macroexp-warn-and-return
>                 (format-message "avoid `lsh'; use `ash' instead")
> @@ -748,7 +754,8 @@ treatment of negative COUNT provided by this function."
>  If LIST is nil, return nil.
>  If N is non-nil, return the Nth-to-last link of LIST.
>  If N is bigger than the length of LIST, return LIST."
> -  (declare (pure t) (side-effect-free t))    ; pure up to mutation
> +  (declare (type (function (list &optional integer) list))
> +           (pure t) (side-effect-free t))    ; pure up to mutation
>    (if n
>        (and (>= n 0)
>             (let ((m (safe-length list)))
> @@ -1585,7 +1592,8 @@ See also `current-global-map'.")
>  
>  (defun eventp (object)
>    "Return non-nil if OBJECT is an input event or event object."
> -  (declare (pure t) (side-effect-free error-free))
> +  (declare (type (function (t) boolean))
> +           (pure t) (side-effect-free error-free))
>    (or (integerp object)
>        (and (if (consp object)
>                 (setq object (car object))
> @@ -1652,7 +1660,8 @@ in the current Emacs session, then this function may return nil."
>  
>  (defsubst mouse-movement-p (object)
>    "Return non-nil if OBJECT is a mouse movement event."
> -  (declare (side-effect-free error-free))
> +  (declare (type (function (t) boolean))
> +           (side-effect-free error-free))
>    (eq (car-safe object) 'mouse-movement))
>  
>  (defun mouse-event-p (object)
> @@ -1961,7 +1970,8 @@ be a list of the form returned by `event-start' and `event-end'."
>  
>  (defun log10 (x)
>    "Return (log X 10), the log base 10 of X."
> -  (declare (side-effect-free t) (obsolete log "24.4"))
> +  (declare (type (function (number) float))
> +           (side-effect-free t) (obsolete log "24.4"))
>    (log x 10))
>  
>  (set-advertised-calling-convention
> @@ -3245,7 +3255,8 @@ It can be retrieved with `(process-get PROCESS PROPNAME)'."
>  
>  (defun memory-limit ()
>    "Return an estimate of Emacs virtual memory usage, divided by 1024."
> -  (declare (side-effect-free error-free))
> +  (declare (type (function () integer))
> +           (side-effect-free error-free))
>    (let ((default-directory temporary-file-directory))
>      (or (cdr (assq 'vsize (process-attributes (emacs-pid)))) 0)))
>  
> @@ -6467,7 +6478,8 @@ To test whether a function can be called interactively, use
>  `commandp'."
>    ;; Kept around for now.  See discussion at:
>    ;; https://lists.gnu.org/r/emacs-devel/2020-08/msg00564.html
> -  (declare (obsolete called-interactively-p "23.2")
> +  (declare (type (function () boolean))
> +           (obsolete called-interactively-p "23.2")
>             (side-effect-free error-free))
>    (called-interactively-p 'interactive))
>  
> diff --git a/lisp/window.el b/lisp/window.el
> index cdc6f690bab..639090752be 100644
> --- a/lisp/window.el
> +++ b/lisp/window.el
> @@ -2515,7 +2515,8 @@ have special meanings:
>  
>  Any other value of ALL-FRAMES means consider all windows on the
>  selected frame and no others."
> -  (declare (side-effect-free error-free))
> +  (declare (type (function (&optional t t t) (or window null)))
> +           (side-effect-free error-free))
>    (let ((windows (window-list-1 nil 'nomini all-frames))
>          best-window best-time second-best-window second-best-time time)
>      (dolist (window windows)
> @@ -2594,7 +2595,8 @@ have special meanings:
>  
>  Any other value of ALL-FRAMES means consider all windows on the
>  selected frame and no others."
> -  (declare (side-effect-free error-free))
> +  (declare (type (function (&optional t t t) (or window null)))
> +           (side-effect-free error-free))
>    (let ((best-size 0)
>  	best-window size)
>      (dolist (window (window-list-1 nil 'nomini all-frames))
> @@ -4089,7 +4091,8 @@ with a special meaning are:
>  
>  Anything else means consider all windows on the selected frame
>  and no others."
> -  (declare (side-effect-free error-free))
> +  (declare (type (function (&optional t t) boolean))
> +           (side-effect-free error-free))
>    (let ((base-window (selected-window)))
>      (if (and nomini (eq base-window (minibuffer-window)))
>  	(setq base-window (next-window base-window)))