cl-preloaded.el: Fix the type lattice

We generally want types to form not just a DAG but a lattice.
If objects can be both `keyword` and `symbol-with-pos`, this
means there should be a more precise type describing this intersection.
If we ever find the need for such a refinement, we could add
such a `keyword-with-pos` type, but here I took the simpler
route of treating `keyword` not as a proper built-in type but
as a second-class type like `natnum`.

While fixing this problem, also fix the problem we had where
`functionp` was not quite adequate to characterize objects of type
`function`, by introducing a new predicate `cl-functionp` for that.

* lisp/emacs-lisp/cl-preloaded.el (cl-functionp): New function.
(function): Use it.
(keyword): Don't declare it as a built-in type.
(user-ptrp): Remove redundant declaration.

* lisp/emacs-lisp/cl-generic.el (cl--generic--unreachable-types):
Delete constant.
(cl-generic-generalizers): Remove corresponding test.

* lisp/emacs-lisp/cl-macs.el (cl-deftype-satisfies): Add entry for
`keyword` type.

* lisp/emacs-lisp/comp.el (comp-known-predicates): Fix type for
negative result of `characterp`.  Remove duplicate `numberp` entry.
Fix types for `keywordp` now that `keyword` is not a built-in type any more.

* test/src/data-tests.el (data-tests--cl-type-of): Add a few cases.
Remove workaround for `function`.

1 files changed, 2 insertions, 9 deletions

diff --git a/lisp/emacs-lisp/cl-generic.el b/lisp/emacs-lisp/cl-generic.el
index 62abe8d1589..8bda857afdd 100644
--- a/lisp/emacs-lisp/cl-generic.el
+++ b/lisp/emacs-lisp/cl-generic.el
@@ -1332,11 +1332,6 @@ These match if the argument is `eql' to VAL."
 
 ;;; Dispatch on "normal types".
 
-(defconst cl--generic--unreachable-types
-  ;; FIXME: Try to make that list empty?
-  '(keyword)
-  "Built-in classes on which we cannot dispatch for technical reasons.")
-
 (defun cl--generic-type-specializers (tag &rest _)
   (and (symbolp tag)
        (let ((class (cl--find-class tag)))
@@ -1350,14 +1345,12 @@ These match if the argument is `eql' to VAL."
 (cl-defmethod cl-generic-generalizers :extra "typeof" (type)
   "Support for dispatch on types.
 This currently works for built-in types and types built on top of records."
-  ;; FIXME: Add support for other types accepted by `cl-typep' such
-  ;; as `character', `face', `function', ...
+  ;; FIXME: Add support for other "types" accepted by `cl-typep' such
+  ;; as `character', `face', `keyword', ...?
   (or
    (and (symbolp type)
         (not (eq type t)) ;; Handled by the `t-generalizer'.
         (let ((class (cl--find-class type)))
-          (when (memq type cl--generic--unreachable-types)
-            (error "Dispatch on %S is currently not supported" type))
           (memq (type-of class)
                 '(built-in-class cl-structure-class eieio--class)))
         (list cl--generic-typeof-generalizer))