Use a dedicated type to represent interpreted-function values

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.

1 files changed, 22 insertions, 16 deletions

diff --git a/lisp/emacs-lisp/cconv.el b/lisp/emacs-lisp/cconv.el
index 4ff47971351..e6a78f07762 100644
--- a/lisp/emacs-lisp/cconv.el
+++ b/lisp/emacs-lisp/cconv.el
@@ -902,7 +902,7 @@ lexically and dynamically bound symbols actually used by FORM."
                                     (delete-dups cconv--dynbindings)))))
         (cons fvs dyns)))))
 
-(defun cconv-make-interpreted-closure (fun env)
+(defun cconv-make-interpreted-closure (args body env docstring iform)
   "Make a closure for the interpreter.
 This is intended to be called at runtime by the ELisp interpreter (when
 the code has not been compiled).
@@ -911,22 +911,27 @@ ENV is the runtime representation of the lexical environment,
 i.e. a list whose elements can be either plain symbols (which indicate
 that this symbol should use dynamic scoping) or pairs (SYMBOL . VALUE)
 for the lexical bindings."
-  (cl-assert (eq (car-safe fun) 'lambda))
+  (cl-assert (consp body))
+  (cl-assert (listp args))
   (let ((lexvars (delq nil (mapcar #'car-safe env))))
-    (if (or (null lexvars)
-            ;; Functions with a `:closure-dont-trim-context' marker
-            ;; should keep their whole context untrimmed (bug#59213).
-            (and (eq :closure-dont-trim-context (nth 2 fun))
-                 ;; Check the function doesn't just return the magic keyword.
-                 (nthcdr 3 fun)))
+    (if (or
+         ;; Functions with a `:closure-dont-trim-context' marker
+         ;; should keep their whole context untrimmed (bug#59213).
+         (and (eq :closure-dont-trim-context (car body))
+              ;; Check the function doesn't just return the magic keyword.
+              (cdr body)
+              ;; Drop the magic marker from the closure.
+              (setq body (cdr body)))
+         ;; There's no var to capture, so skip the analysis.
+         (null lexvars))
         ;; The lexical environment is empty, or needs to be preserved,
         ;; so there's no need to look for free variables.
-        ;; Attempting to replace ,(cdr fun) by a macroexpanded version
-        ;; causes bootstrap to fail.
-        `(closure ,env . ,(cdr fun))
+        ;; Attempting to replace body by a macroexpanded version
+        ;; caused bootstrap to fail.
+        (make-interpreted-closure args body env docstring iform)
       ;; We could try and cache the result of the macroexpansion and
       ;; `cconv-fv' analysis.  Not sure it's worth the trouble.
-      (let* ((form `#',fun)
+      (let* ((form `#'(lambda ,args ,iform . ,body))
              (expanded-form
               (let ((lexical-binding t) ;; Tell macros which dialect is in use.
 	            ;; Make the macro aware of any defvar declarations in scope.
@@ -935,10 +940,10 @@ for the lexical bindings."
                          (append env macroexp--dynvars) env)))
                 (macroexpand-all form macroexpand-all-environment)))
              ;; Since we macroexpanded the body, we may as well use that.
-             (expanded-fun-cdr
+             (expanded-fun-body
               (pcase expanded-form
-                (`#'(lambda . ,cdr) cdr)
-                (_ (cdr fun))))
+                (`#'(lambda ,_args ,_iform . ,newbody) newbody)
+                (_ body)))
 
              (dynvars (delq nil (mapcar (lambda (b) (if (symbolp b) b)) env)))
              (fvs (cconv-fv expanded-form lexvars dynvars))
@@ -946,7 +951,8 @@ for the lexical bindings."
                             (cdr fvs))))
         ;; Never return a nil env, since nil means to use the dynbind
         ;; dialect of ELisp.
-        `(closure ,(or newenv '(t)) . ,expanded-fun-cdr)))))
+        (make-interpreted-closure args expanded-fun-body (or newenv '(t))
+                                  docstring iform)))))
 
 
 (provide 'cconv)