Use a dedicated type to represent interpreted-function valuesscratch/interpreted-function

Change `function` so that when evaluating #'(lambda ...)
we return an object of type `interpreted-function` rather than
a list starting with one of `lambda` or `closure`.
The new type reuses the existing PVEC_CLOSURE (nee PVEC_COMPILED)
tag and tries to align the corresponding elements:

- the arglist, the docstring, and the interactive-form go in the
  same slots as for byte-code functions.
- the body of the function goes in the slot used for the bytecode string.
- the lexical context goes in the slot used for the constants of
  bytecoded functions.

The first point above means that `help-function-arglist`,
`documentation`, and `interactive-form`s don't need to
distinguish interpreted and bytecode functions any more.

Main benefits of the change:

- We can now reliably distinguish a list from a function value.
- `cl-defmethod` can dispatch on `interactive-function` and `closure`.
  Dispatch on `function` also works now for interpreted functions but still
  won't work for functions represented as lists or as symbols, of course.
- Function values are now self-evaluating.  That was alrready the case
  when byte-compiled, but not when interpreted since
  (eval '(closure ...)) signals a void-function error.
  That also avoids false-positive warnings about "don't quote your lambdas"
  when doing things like `(mapcar ',func ...)`.

* src/eval.c (Fmake_interpreted_closure): New function.
(Ffunction): Use it and change calling convention of
`Vinternal_make_interpreted_closure_function`.
(FUNCTIONP, Fcommandp, eval_sub, funcall_general, funcall_lambda)
(Ffunc_arity, lambda_arity): Simplify.
(funcall_lambda): Adjust to new representation.
(syms_of_eval): `defsubr` the new function.  Remove definition of `Qclosure`.

* lisp/emacs-lisp/cconv.el (cconv-make-interpreted-closure):
Change calling convention and use `make-interpreted-closure`.

* src/data.c (Fcl_type_of): Distinguish `byte-code-function`s from
`interpreted-function`s.
(Fclosurep, finterpreted_function_p): New functions.
(Fbyte_code_function_p): Don't be confused by `interpreted-function`s.
(Finteractive_form, Fcommand_modes): Simplify.
(syms_of_data): Define new type symbols and `defsubr` the two
new functions.

* lisp/emacs-lisp/cl-print.el (cl-print-object) <interpreted-function>:
New method.

* lisp/emacs-lisp/oclosure.el (oclosure): Refine the parent
to be `closure`.
(oclosure--fix-type, oclosure-type): Simplify.
(oclosure--copy, oclosure--get, oclosure--set): Adjust to
new representation.

* src/callint.c (Fcall_interactively): Adjust to new representation.

* src/lread.c (bytecode_from_rev_list):

* lisp/simple.el (function-documentation):
* lisp/help.el (help-function-arglist): Remove the old `closure` case
and adjust the byte-code case so it handles `interpreted-function`s.

* lisp/emacs-lisp/cl-preloaded.el (closure): New type.
(byte-code-function): Add it as a parent.
(interpreted-function): Adjust parent (the type itself was already
added earlier by accident).

* lisp/emacs-lisp/bytecomp.el (byte-compile--reify-function): Adjust to
new representation.
(byte-compile): Use `interpreted-function-p`.

* lisp/emacs-lisp/byte-opt.el (byte-compile-inline-expand): Adjust to
new representation.
(side-effect-free-fns): Add `interpreted-function-p` and `closurep`.

* src/profiler.c (trace_hash, ffunction_equal): Simplify.
* lisp/profiler.el (profiler-function-equal): Simplify.

* lisp/emacs-lisp/nadvice.el (advice--interactive-form-1):
Use `interpreted-function-p`; adjust to new representation; and take
advantage of the fact that function values are now self-evaluating.

* lisp/emacs-lisp/lisp-mode.el (closure):
Remove `lisp-indent-function` property.

* lisp/emacs-lisp/disass.el (disassemble-internal): Adjust to
new representation.
* lisp/emacs-lisp/edebug.el (edebug--strip-instrumentation):
Use `interpreted-function-p`.
* lisp/emacs-lisp/comp-common.el (comp-known-type-specifiers):
Add `closurep` and `interpreted-function-p`.

* test/lisp/help-fns-tests.el (help-fns-test-lisp-defun): Adjust to
more precise type info in `describe-function`.
* test/lisp/erc/resources/erc-d/erc-d-tests.el (erc-d--render-entries):
Use `interpreted-function-p`.
* test/lisp/emacs-lisp/macroexp-resources/vk.el (vk-f4, vk-f5):
Don't hardcode function values.

* doc/lispref/functions.texi (Anonymous Functions): Don't suggest that
function values are lists.  Reword "self-quoting" to reflect the
fact that #' doesn't return the exact same object.  Update examples
with the new shape of the return value.

* doc/lispref/variables.texi (Lexical Binding):
* doc/lispref/lists.texi (Rearrangement):
* doc/lispref/control.texi (Handling Errors): Update examples to reflect
new representation of function values.

3 files changed, 33 insertions, 30 deletions

diff --git a/test/lisp/emacs-lisp/macroexp-resources/vk.el b/test/lisp/emacs-lisp/macroexp-resources/vk.el
index 5358bcaeb5c..c59a6b9f8f1 100644
--- a/test/lisp/emacs-lisp/macroexp-resources/vk.el
+++ b/test/lisp/emacs-lisp/macroexp-resources/vk.el
@@ -78,29 +78,31 @@
 
 (defconst vk-val3 (eval-when-compile (vk-f3 0)))
 
-(defconst vk-f4 '(lambda (x)
-                   (defvar vk-v4)
-                   (let ((vk-v4 31)
-                         (y 32))
-                     (ignore vk-v4 x y)
-                     (list
-                      (vk-variable-kind vk-a)   ; dyn
-                      (vk-variable-kind vk-b)   ; dyn
-                      (vk-variable-kind vk-v4)  ; dyn
-                      (vk-variable-kind x)      ; dyn
-                      (vk-variable-kind y)))))  ; dyn
-
-(defconst vk-f5 '(closure (t) (x)
-                   (defvar vk-v5)
-                   (let ((vk-v5 41)
-                         (y 42))
-                     (ignore vk-v5 x y)
-                     (list
-                      (vk-variable-kind vk-a)   ; dyn
-                      (vk-variable-kind vk-b)   ; dyn
-                      (vk-variable-kind vk-v5)  ; dyn
-                      (vk-variable-kind x)      ; lex
-                      (vk-variable-kind y)))))  ; lex
+(defconst vk-f4 (eval '(lambda (x)
+                         (defvar vk-v4)
+                         (let ((vk-v4 31)
+                               (y 32))
+                           (ignore vk-v4 x y)
+                           (list
+                            (vk-variable-kind vk-a) ; dyn
+                            (vk-variable-kind vk-b) ; dyn
+                            (vk-variable-kind vk-v4) ; dyn
+                            (vk-variable-kind x)     ; dyn
+                            (vk-variable-kind y))))  ; dyn
+                      nil))
+
+(defconst vk-f5 (eval '(lambda (x)
+                         (defvar vk-v5)
+                         (let ((vk-v5 41)
+                               (y 42))
+                           (ignore vk-v5 x y)
+                           (list
+                            (vk-variable-kind vk-a) ; dyn
+                            (vk-variable-kind vk-b) ; dyn
+                            (vk-variable-kind vk-v5) ; dyn
+                            (vk-variable-kind x)     ; lex
+                            (vk-variable-kind y))))  ; lex
+                      t))
 
 (defun vk-f6 ()
   (eval '(progn
diff --git a/test/lisp/erc/resources/erc-d/erc-d-tests.el b/test/lisp/erc/resources/erc-d/erc-d-tests.el
index 78f87399afb..dda1b1ced84 100644
--- a/test/lisp/erc/resources/erc-d/erc-d-tests.el
+++ b/test/lisp/erc/resources/erc-d/erc-d-tests.el
@@ -367,8 +367,9 @@
       (should (equal (funcall it) "foo3foo")))
 
     (ert-info ("Exits clean")
-      (when (listp (alist-get 'f (erc-d-dialog-vars dialog))) ; may be compiled
-        (should (eq 'closure (car (alist-get 'f (erc-d-dialog-vars dialog))))))
+      (when (interpreted-function-p
+             (alist-get 'f (erc-d-dialog-vars dialog))) ; may be compiled
+        (should (aref (alist-get 'f (erc-d-dialog-vars dialog)) 2)))
       (should-not (funcall it))
       (should (equal (erc-d-dialog-vars dialog)
                      `((:a . 1)
diff --git a/test/lisp/help-fns-tests.el b/test/lisp/help-fns-tests.el
index 1beeb77640c..82350a4bc71 100644
--- a/test/lisp/help-fns-tests.el
+++ b/test/lisp/help-fns-tests.el
@@ -63,14 +63,14 @@ Return first line of the output of (describe-function-1 FUNC)."
     (should (string-match regexp result))))
 
 (ert-deftest help-fns-test-lisp-defun ()
-  (let ((regexp (if (featurep 'native-compile)
-                    "a subr-native-elisp in .+subr\\.el"
-                  "a compiled-function in .+subr\\.el"))
+  (let ((regexp "a \\([^ ]+\\) in .+subr\\.el")
         (result (help-fns-tests--describe-function 'last)))
-    (should (string-match regexp result))))
+    (should (string-match regexp result))
+    (should (member (match-string 1 result)
+                    '("subr-native-elisp" "byte-code-function")))))
 
 (ert-deftest help-fns-test-lisp-defsubst ()
-  (let ((regexp "a compiled-function in .+subr\\.el")
+  (let ((regexp "a byte-code-function in .+subr\\.el")
         (result (help-fns-tests--describe-function 'posn-window)))
     (should (string-match regexp result))))