cl-typep: Emit warning when using a type not known to be a type

`cl-typep` has used a heuristic that if there's a `<foo>-p` function,
then <foo> can be used as a type.  This made sense in the past where
most types were not officially declared to be (cl-)types, but nowadays
this just encourages abuses such as using `cl-typecase` with
"types" like `fbound`.  It's also a problem for EIEIO objects, where
for historical reasons `<foo>-p` tests if the object is of type
exactly `<foo>` whereas (cl-typep OBJ <foo>) should instead test
if OBJ is a *subtype* of `<foo>`.

So we change `cl-typep` to emit a warning whenever this "-p" heuristic
is used, to discourage abuses, encourage the use of explicit
`cl-deftype` declarations, and try and detect some misuses of
`<foo>-p` for EIEIO objects.

* lisp/emacs-lisp/eieio.el (defclass): Define as type not only at
run-time but also for the current compilation unit.

* lisp/emacs-lisp/eieio-core.el (class, eieio-object): Define as types.

* lisp/emacs-lisp/cl-preloaded.el (cl-struct-define): Don't abuse the
"-p" heuristic.

* lisp/emacs-lisp/cl-macs.el (cl-deftype-satisfies):
Add entries for frames, windows, markers, and overlays.
(cl-typep): Emit a warning when using a predicate that is not known to
correspond to a type.

* lisp/files.el (file-relative-name): Fix error that can trigger if
there's an(other) error between loading `files.el` and loading
`minibuffer.el`.

1 files changed, 4 insertions, 0 deletions

diff --git a/lisp/emacs-lisp/eieio-core.el b/lisp/emacs-lisp/eieio-core.el
index d687289b22f..d9864e6965d 100644
--- a/lisp/emacs-lisp/eieio-core.el
+++ b/lisp/emacs-lisp/eieio-core.el
@@ -137,6 +137,8 @@ Currently under control of this var:
 X can also be is a symbol."
   (eieio--class-p (if (symbolp x) (cl--find-class x) x)))
 
+(cl-deftype class () `(satisfies class-p))
+
 (defun eieio--class-print-name (class)
   "Return a printed representation of CLASS."
   (format "#<class %s>" (eieio-class-name class)))
@@ -165,6 +167,8 @@ Return nil if that option doesn't exist."
   (and (recordp obj)
        (eieio--class-p (eieio--object-class obj))))
 
+(cl-deftype eieio-object () `(satisfies eieio-object-p))
+
 (define-obsolete-function-alias 'object-p #'eieio-object-p "25.1")
 
 (defun class-abstract-p (class)