Re: Inferred function types in the *Help* buffer

[Andrea Corallo <acorallo@gnu.org>]

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Andrea Corallo <akrl@sdf.org> writes:

> Eli Zaretskii <eliz@gnu.org> writes:
>
>>> From: Andrea Corallo <akrl@sdf.org>
>>> Date: Tue, 23 May 2023 16:44:08 +0000
>>> 
>>> foo is a native-compiled Lisp function in
>>> ‘~/.emacs.d/eln-cache/30.0.50-e29d76eb/test-a526a80f-5481bc95.eln’.
>>
>> Why does it name the .eln file, not its source .el file?  Or is this
>> the case when there's no .el file?
>
> I believe we show the .eln when this is loaded directly like (load
> "xxx.eln"), IOW when we have no information on the original source.
>
>>> Signature: (foo N)
>>> 
>>> Inferred type: (function (t) (or (member to-small too-big) (integer
>>> 100 100)))
>>
>> Can you explain what is this "Inferred type" information about?
>
> Sure, the native compiler in the attempt of optimizing the code is
> propagating value type informations over the code being compiled.
>
> The inferred type is formed using the arglist of the function (ATM is
> not possible to specify types for arguments so they are all of type t)
> and the return type.  The return type is nothing more than the union of
> all types inferred by the compiler at the various return point of the
> function.
>
> At the time I wrote something about this here
> <https://akrl.sdf.org/gccemacs.html#orge596749>.
>
> Also for more about CL type specifiers
> <https://www.cs.cmu.edu/Groups/AI/html/cltl/clm/node44.html>.
>
>>> ATM I adds as well "Signature: " in front of the signature to
>>> differentiate it from the type.  But looking at it in restrospective it
>>> might be not even necessary.
>>
>> We should probably preserve the current format of just showing the
>> signature without any headings.
>
> Agreed.

Okay I installed ecc1d990d9e into master to implement this, please let
me know if the entry in NEWS can be improved or feel free to just do it
(I'm terrible at writing).

Also I'd like to improve this feature to list also the function types
that are known to the compiler (Read `comp-known-type-specifiers').  ATM
they lives in comp.el but would be better to move them out.

Ideally I think we should have a declare syntax and maybe an extention
to the DEFUN macro to cover for primitives as well, in order to have
these declaration where each function is defined.  But probably for now
something like the attached patch is sufficient and considerably less
invasive?

My main questions are: is subr-x.el the right place to move them in?  If
not which one?  Should be `comp-known-type-specifiers' be renamed into
something else or it's okay?

Thanks

  Andrea


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From 977046f8979b4f18f6be358a2d3d6aaefe5ffcd6 Mon Sep 17 00:00:00 2001
From: Andrea Corallo <akrl@sdf.org>
Date: Tue, 30 May 2023 15:30:11 +0200
Subject: [PATCH] Print know function types in C-h f

* lisp/emacs-lisp/subr-x.el (comp-known-type-specifiers): Move to
subr-x.el.
* lisp/help-fns.el (help-fns--signature): Make use of
`comp-known-type-specifiers' for printing more function types.
---
 lisp/emacs-lisp/comp.el   | 317 +-------------------------------------
 lisp/emacs-lisp/subr-x.el | 315 +++++++++++++++++++++++++++++++++++++
 lisp/help-fns.el          |  10 +-
 3 files changed, 322 insertions(+), 320 deletions(-)

diff --git a/lisp/emacs-lisp/comp.el b/lisp/emacs-lisp/comp.el
index ec51f805c2b..6d9270ba0b7 100644
--- a/lisp/emacs-lisp/comp.el
+++ b/lisp/emacs-lisp/comp.el
@@ -275,322 +275,7 @@ comp-post-pass-hooks
 Useful to hook into pass checkers.")
 
 ;; FIXME this probably should not be here but... good for now.
-(defconst comp-known-type-specifiers
-  `(
-    ;; Functions we can trust not to be or if redefined should expose
-    ;; the same type.  Vast majority of these is either pure or
-    ;; primitive, the original list is the union of pure +
-    ;; side-effect-free-fns + side-effect-and-error-free-fns:
-    (% (function ((or number marker) (or number marker)) number))
-    (* (function (&rest (or number marker)) number))
-    (+ (function (&rest (or number marker)) number))
-    (- (function (&rest (or number marker)) number))
-    (/ (function ((or number marker) &rest (or number marker)) number))
-    (/= (function ((or number marker) (or number marker)) boolean))
-    (1+ (function ((or number marker)) number))
-    (1- (function ((or number marker)) number))
-    (< (function ((or number marker) &rest (or number marker)) boolean))
-    (<= (function ((or number marker) &rest (or number marker)) boolean))
-    (= (function ((or number marker) &rest (or number marker)) boolean))
-    (> (function ((or number marker) &rest (or number marker)) boolean))
-    (>= (function ((or number marker) &rest (or number marker)) boolean))
-    (abs (function (number) number))
-    (acos (function (number) float))
-    (append (function (&rest t) t))
-    (aref (function (t fixnum) t))
-    (arrayp (function (t) boolean))
-    (ash (function (integer integer) integer))
-    (asin (function (number) float))
-    (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 (function (bool-vector boolean integer) fixnum))
-    (bool-vector-count-population (function (bool-vector) fixnum))
-    (bool-vector-not (function (bool-vector &optional bool-vector) bool-vector))
-    (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))
-    (buffer-modified-p (function (&optional buffer) boolean))
-    (buffer-size (function (&optional buffer) integer))
-    (buffer-string (function () string))
-    (buffer-substring (function ((or integer marker) (or integer marker)) string))
-    (bufferp (function (t) boolean))
-    (byte-code-function-p (function (t) boolean))
-    (capitalize (function (or integer string) (or integer string)))
-    (car (function (list) t))
-    (car-less-than-car (function (list list) boolean))
-    (car-safe (function (t) t))
-    (case-table-p (function (t) boolean))
-    (cdr (function (list) t))
-    (cdr-safe (function (t) t))
-    (ceiling (function (number &optional number) integer))
-    (char-after (function (&optional (or marker integer)) (or fixnum null)))
-    (char-before (function (&optional (or marker integer)) (or fixnum null)))
-    (char-equal (function (integer integer) boolean))
-    (char-or-string-p (function (t) boolean))
-    (char-to-string (function (fixnum) string))
-    (char-width (function (fixnum) fixnum))
-    (characterp (function (t &optional t) boolean))
-    (charsetp (function (t) boolean))
-    (commandp (function (t &optional t) boolean))
-    (compare-strings (function (string (or integer marker null) (or integer marker null) string (or integer marker null) (or integer marker null) &optional t) (or (member t) fixnum)))
-    (concat (function (&rest sequence) string))
-    (cons (function (t t) cons))
-    (consp (function (t) boolean))
-    (coordinates-in-window-p (function (cons window) boolean))
-    (copy-alist (function (list) list))
-    (copy-marker (function (&optional (or integer marker) boolean) marker))
-    (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))
-    (current-local-map (function () (or cons null)))
-    (current-minor-mode-maps (function () (or cons null)))
-    (current-time (function () cons))
-    (current-time-string (function (&optional (or number list)
-                                              (or symbol string cons integer))
-                                   string))
-    (current-time-zone (function (&optional (or number list)
-                                            (or symbol string cons integer))
-                                 cons))
-    (custom-variable-p (function (symbol) boolean))
-    (decode-char (function (cons t) (or fixnum null)))
-    (decode-time (function (&optional (or number list)
-                                      (or symbol string cons integer)
-                                      symbol)
-                           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)))
-    (elt (function (sequence integer) t))
-    (encode-char (function (fixnum symbol) (or fixnum null)))
-    (encode-time (function (cons &rest t) cons))
-    (eobp (function () boolean))
-    (eolp (function () boolean))
-    (eq (function (t t) boolean))
-    (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) float))
-    (fboundp (function (symbol) boolean))
-    (fceiling (function (float) float))
-    (featurep (function (symbol &optional symbol) boolean))
-    (ffloor (function (float) float))
-    (file-directory-p (function (string) boolean))
-    (file-exists-p (function (string) boolean))
-    (file-locked-p (function (string) boolean))
-    (file-name-absolute-p (function (string) boolean))
-    (file-newer-than-file-p (function (string string) boolean))
-    (file-readable-p (function (string) boolean))
-    (file-symlink-p (function (string) boolean))
-    (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))
-    (floor (function (number &optional number) integer))
-    (following-char (function () fixnum))
-    (format (function (string &rest t) string))
-    (format-time-string (function (string &optional (or number list)
-                                          (or symbol string cons integer))
-                                  string))
-    (frame-first-window (function ((or frame window)) window))
-    (frame-root-window (function (&optional (or frame window)) window))
-    (frame-selected-window (function (&optional (or frame window)) window))
-    (frame-visible-p (function (frame) boolean))
-    (framep (function (t) boolean))
-    (fround (function (float) float))
-    (ftruncate (function (float) float))
-    (get (function (symbol symbol) t))
-    (get-buffer (function ((or buffer string)) (or buffer null)))
-    (get-buffer-window (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 vector) symbol))
-    (invocation-directory (function () string))
-    (invocation-name (function () string))
-    (isnan (function (float) boolean))
-    (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))
-    (length= (function (sequence fixnum) boolean))
-    (length> (function (sequence fixnum) boolean))
-    (line-beginning-position (function (&optional integer) integer))
-    (line-end-position (function (&optional integer) integer))
-    (list (function (&rest t) list))
-    (listp (function (t) boolean))
-    (local-variable-if-set-p (function (symbol &optional buffer) boolean))
-    (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))
-    (logior (function (&rest (or integer marker)) integer))
-    (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) vector))
-    (make-list (function (integer t) list))
-    (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))
-    (minibuffer-selected-window (function () (or window null)))
-    (minibuffer-window (function (&optional frame) window))
-    (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))
-    (nlistp (function (t) boolean))
-    (not (function (t) boolean))
-    (nth (function (integer list) t))
-    (nthcdr (function (integer t) t))
-    (null (function (t) boolean))
-    (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) cons))
-    (plist-get (function (list t &optional t) t))
-    (plist-member (function (list t &optional t) list))
-    (point (function () integer))
-    (point-marker (function () marker))
-    (point-max (function () integer))
-    (point-min (function () integer))
-    (preceding-char (function () fixnum))
-    (previous-window (function (&optional window t t) window))
-    (prin1-to-string (function (t &optional t t) string))
-    (processp (function (t) boolean))
-    (proper-list-p (function (t) boolean))
-    (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))
-    (reverse (function (sequence) sequence))
-    (round (function (number &optional number) integer))
-    (safe-length (function (t) integer))
-    (selected-frame (function () frame))
-    (selected-window (function () window))
-    (sequencep (function (t) boolean))
-    (sin (function (number) float))
-    (sqrt (function (number) float))
-    (standard-case-table (function () char-table))
-    (standard-syntax-table (function () char-table))
-    (string (function (&rest fixnum) string))
-    (string-as-multibyte (function (string) string))
-    (string-as-unibyte (function (string) string))
-    (string-equal (function ((or string symbol) (or string symbol)) boolean))
-    (string-lessp (function ((or string symbol) (or string symbol)) boolean))
-    (string-make-multibyte (function (string) string))
-    (string-make-unibyte (function (string) string))
-    (string-search (function (string string &optional integer) (or integer null)))
-    (string-to-char (function (string) fixnum))
-    (string-to-multibyte (function (string) string))
-    (string-to-number (function (string &optional integer) number))
-    (string-to-syntax (function (string) (or cons null)))
-    (string< (function ((or string symbol) (or string symbol)) boolean))
-    (string= (function ((or string symbol) (or string symbol)) boolean))
-    (stringp (function (t) boolean))
-    (subrp (function (t) boolean))
-    (substring (function ((or string vector) &optional integer integer) (or string vector)))
-    (sxhash (function (t) integer))
-    (sxhash-eq (function (t) integer))
-    (sxhash-eql (function (t) integer))
-    (sxhash-equal (function (t) integer))
-    (symbol-function (function (symbol) t))
-    (symbol-name (function (symbol) string))
-    (symbol-plist (function (symbol) list))
-    (symbol-value (function (symbol) t))
-    (symbolp (function (t) boolean))
-    (syntax-table (function () char-table))
-    (syntax-table-p (function (t) boolean))
-    (tan (function (number) float))
-    (this-command-keys (function () string))
-    (this-command-keys-vector (function () vector))
-    (this-single-command-keys (function () vector))
-    (this-single-command-raw-keys (function () vector))
-    (time-convert (function ((or number list) &optional (or symbol integer))
-                            (or cons number)))
-    (truncate (function (number &optional number) integer))
-    (type-of (function (t) symbol))
-    (unibyte-char-to-multibyte (function (fixnum) fixnum)) ;; byte is fixnum
-    (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))
-    (vconcat (function (&rest sequence) vector))
-    (vector (function (&rest t) vector))
-    (vectorp (function (t) boolean))
-    (visible-frame-list (function () list))
-    (wholenump (function (t) boolean))
-    (window-configuration-p (function (t) boolean))
-    (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.")
+
 
 (defconst comp-known-func-cstr-h
   (cl-loop
diff --git a/lisp/emacs-lisp/subr-x.el b/lisp/emacs-lisp/subr-x.el
index 9e906930b92..d9a32b950bb 100644
--- a/lisp/emacs-lisp/subr-x.el
+++ b/lisp/emacs-lisp/subr-x.el
@@ -37,6 +37,321 @@
 
 (eval-when-compile (require 'cl-lib))
 
+(defconst comp-known-type-specifiers
+  ;; Functions we can trust not to be redefined or if redefined should
+  ;; expose the same type.  The vast majority of these is either
+  ;; pure or primitive, the original list is the union of pure +
+  ;; side-effect-free-fns + side-effect-and-error-free-fns:
+  `((% (function ((or number marker) (or number marker)) number))
+    (* (function (&rest (or number marker)) number))
+    (+ (function (&rest (or number marker)) number))
+    (- (function (&rest (or number marker)) number))
+    (/ (function ((or number marker) &rest (or number marker)) number))
+    (/= (function ((or number marker) (or number marker)) boolean))
+    (1+ (function ((or number marker)) number))
+    (1- (function ((or number marker)) number))
+    (< (function ((or number marker) &rest (or number marker)) boolean))
+    (<= (function ((or number marker) &rest (or number marker)) boolean))
+    (= (function ((or number marker) &rest (or number marker)) boolean))
+    (> (function ((or number marker) &rest (or number marker)) boolean))
+    (>= (function ((or number marker) &rest (or number marker)) boolean))
+    (abs (function (number) number))
+    (acos (function (number) float))
+    (append (function (&rest t) t))
+    (aref (function (t fixnum) t))
+    (arrayp (function (t) boolean))
+    (ash (function (integer integer) integer))
+    (asin (function (number) float))
+    (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 (function (bool-vector boolean integer) fixnum))
+    (bool-vector-count-population (function (bool-vector) fixnum))
+    (bool-vector-not (function (bool-vector &optional bool-vector) bool-vector))
+    (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))
+    (buffer-modified-p (function (&optional buffer) boolean))
+    (buffer-size (function (&optional buffer) integer))
+    (buffer-string (function () string))
+    (buffer-substring (function ((or integer marker) (or integer marker)) string))
+    (bufferp (function (t) boolean))
+    (byte-code-function-p (function (t) boolean))
+    (capitalize (function (or integer string) (or integer string)))
+    (car (function (list) t))
+    (car-less-than-car (function (list list) boolean))
+    (car-safe (function (t) t))
+    (case-table-p (function (t) boolean))
+    (cdr (function (list) t))
+    (cdr-safe (function (t) t))
+    (ceiling (function (number &optional number) integer))
+    (char-after (function (&optional (or marker integer)) (or fixnum null)))
+    (char-before (function (&optional (or marker integer)) (or fixnum null)))
+    (char-equal (function (integer integer) boolean))
+    (char-or-string-p (function (t) boolean))
+    (char-to-string (function (fixnum) string))
+    (char-width (function (fixnum) fixnum))
+    (characterp (function (t &optional t) boolean))
+    (charsetp (function (t) boolean))
+    (commandp (function (t &optional t) boolean))
+    (compare-strings (function (string (or integer marker null) (or integer marker null) string (or integer marker null) (or integer marker null) &optional t) (or (member t) fixnum)))
+    (concat (function (&rest sequence) string))
+    (cons (function (t t) cons))
+    (consp (function (t) boolean))
+    (coordinates-in-window-p (function (cons window) boolean))
+    (copy-alist (function (list) list))
+    (copy-marker (function (&optional (or integer marker) boolean) marker))
+    (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))
+    (current-local-map (function () (or cons null)))
+    (current-minor-mode-maps (function () (or cons null)))
+    (current-time (function () cons))
+    (current-time-string (function (&optional (or number list)
+                                              (or symbol string cons integer))
+                                   string))
+    (current-time-zone (function (&optional (or number list)
+                                            (or symbol string cons integer))
+                                 cons))
+    (custom-variable-p (function (symbol) boolean))
+    (decode-char (function (cons t) (or fixnum null)))
+    (decode-time (function (&optional (or number list)
+                                      (or symbol string cons integer)
+                                      symbol)
+                           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)))
+    (elt (function (sequence integer) t))
+    (encode-char (function (fixnum symbol) (or fixnum null)))
+    (encode-time (function (cons &rest t) cons))
+    (eobp (function () boolean))
+    (eolp (function () boolean))
+    (eq (function (t t) boolean))
+    (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) float))
+    (fboundp (function (symbol) boolean))
+    (fceiling (function (float) float))
+    (featurep (function (symbol &optional symbol) boolean))
+    (ffloor (function (float) float))
+    (file-directory-p (function (string) boolean))
+    (file-exists-p (function (string) boolean))
+    (file-locked-p (function (string) boolean))
+    (file-name-absolute-p (function (string) boolean))
+    (file-newer-than-file-p (function (string string) boolean))
+    (file-readable-p (function (string) boolean))
+    (file-symlink-p (function (string) boolean))
+    (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))
+    (floor (function (number &optional number) integer))
+    (following-char (function () fixnum))
+    (format (function (string &rest t) string))
+    (format-time-string (function (string &optional (or number list)
+                                          (or symbol string cons integer))
+                                  string))
+    (frame-first-window (function ((or frame window)) window))
+    (frame-root-window (function (&optional (or frame window)) window))
+    (frame-selected-window (function (&optional (or frame window)) window))
+    (frame-visible-p (function (frame) boolean))
+    (framep (function (t) boolean))
+    (fround (function (float) float))
+    (ftruncate (function (float) float))
+    (get (function (symbol symbol) t))
+    (get-buffer (function ((or buffer string)) (or buffer null)))
+    (get-buffer-window (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 vector) symbol))
+    (invocation-directory (function () string))
+    (invocation-name (function () string))
+    (isnan (function (float) boolean))
+    (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))
+    (length= (function (sequence fixnum) boolean))
+    (length> (function (sequence fixnum) boolean))
+    (line-beginning-position (function (&optional integer) integer))
+    (line-end-position (function (&optional integer) integer))
+    (list (function (&rest t) list))
+    (listp (function (t) boolean))
+    (local-variable-if-set-p (function (symbol &optional buffer) boolean))
+    (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))
+    (logior (function (&rest (or integer marker)) integer))
+    (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) vector))
+    (make-list (function (integer t) list))
+    (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))
+    (minibuffer-selected-window (function () (or window null)))
+    (minibuffer-window (function (&optional frame) window))
+    (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))
+    (nlistp (function (t) boolean))
+    (not (function (t) boolean))
+    (nth (function (integer list) t))
+    (nthcdr (function (integer t) t))
+    (null (function (t) boolean))
+    (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) cons))
+    (plist-get (function (list t &optional t) t))
+    (plist-member (function (list t &optional t) list))
+    (point (function () integer))
+    (point-marker (function () marker))
+    (point-max (function () integer))
+    (point-min (function () integer))
+    (preceding-char (function () fixnum))
+    (previous-window (function (&optional window t t) window))
+    (prin1-to-string (function (t &optional t t) string))
+    (processp (function (t) boolean))
+    (proper-list-p (function (t) boolean))
+    (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))
+    (reverse (function (sequence) sequence))
+    (round (function (number &optional number) integer))
+    (safe-length (function (t) integer))
+    (selected-frame (function () frame))
+    (selected-window (function () window))
+    (sequencep (function (t) boolean))
+    (sin (function (number) float))
+    (sqrt (function (number) float))
+    (standard-case-table (function () char-table))
+    (standard-syntax-table (function () char-table))
+    (string (function (&rest fixnum) string))
+    (string-as-multibyte (function (string) string))
+    (string-as-unibyte (function (string) string))
+    (string-equal (function ((or string symbol) (or string symbol)) boolean))
+    (string-lessp (function ((or string symbol) (or string symbol)) boolean))
+    (string-make-multibyte (function (string) string))
+    (string-make-unibyte (function (string) string))
+    (string-search (function (string string &optional integer) (or integer null)))
+    (string-to-char (function (string) fixnum))
+    (string-to-multibyte (function (string) string))
+    (string-to-number (function (string &optional integer) number))
+    (string-to-syntax (function (string) (or cons null)))
+    (string< (function ((or string symbol) (or string symbol)) boolean))
+    (string= (function ((or string symbol) (or string symbol)) boolean))
+    (stringp (function (t) boolean))
+    (subrp (function (t) boolean))
+    (substring (function ((or string vector) &optional integer integer) (or string vector)))
+    (sxhash (function (t) integer))
+    (sxhash-eq (function (t) integer))
+    (sxhash-eql (function (t) integer))
+    (sxhash-equal (function (t) integer))
+    (symbol-function (function (symbol) t))
+    (symbol-name (function (symbol) string))
+    (symbol-plist (function (symbol) list))
+    (symbol-value (function (symbol) t))
+    (symbolp (function (t) boolean))
+    (syntax-table (function () char-table))
+    (syntax-table-p (function (t) boolean))
+    (tan (function (number) float))
+    (this-command-keys (function () string))
+    (this-command-keys-vector (function () vector))
+    (this-single-command-keys (function () vector))
+    (this-single-command-raw-keys (function () vector))
+    (time-convert (function ((or number list) &optional (or symbol integer))
+                            (or cons number)))
+    (truncate (function (number &optional number) integer))
+    (type-of (function (t) symbol))
+    (unibyte-char-to-multibyte (function (fixnum) fixnum)) ;; byte is fixnum
+    (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))
+    (vconcat (function (&rest sequence) vector))
+    (vector (function (&rest t) vector))
+    (vectorp (function (t) boolean))
+    (visible-frame-list (function () list))
+    (wholenump (function (t) boolean))
+    (window-configuration-p (function (t) boolean))
+    (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.")
 
 (defmacro internal--thread-argument (first? &rest forms)
   "Internal implementation for `thread-first' and `thread-last'.
diff --git a/lisp/help-fns.el b/lisp/help-fns.el
index c4e09e48bea..af1c37f2d86 100644
--- a/lisp/help-fns.el
+++ b/lisp/help-fns.el
@@ -711,10 +711,12 @@ help-fns--signature
           (unless (and (symbolp function)
                        (get function 'reader-construct))
             (insert high-usage "\n")
-            (when (and (featurep 'native-compile)
-                       (subr-native-elisp-p (symbol-function function))
-                       (subr-type (symbol-function function)))
-              (insert (format "\nInferred type: %s\n" (subr-type (symbol-function function))))))
+            (if-let ((entry (assoc function comp-known-type-specifiers)))
+                (insert (format "\nType: %s\n" (car (cdr entry))))
+              (when (and (featurep 'native-compile)
+                         (subr-native-elisp-p (symbol-function function))
+                         (subr-type (symbol-function function)))
+                (insert (format "\nInferred type: %s\n" (subr-type (symbol-function function)))))))
           (fill-region fill-begin (point))
           high-doc)))))
 
-- 
2.25.1