Re: feature/type-hierarchy 8a63e50036f 1/5: * Define 'cl--type-hierarchy' and compute 'cl--typeof-types' from it

[Stefan Monnier]

> -(defconst cl--typeof-types
> -  ;; Hand made from the source code of `type-of'.
> -  '((integer number integer-or-marker number-or-marker atom)
> -    (symbol-with-pos symbol atom) (symbol atom) (string array sequence atom)
[...]
> +(defconst cl--type-hierarchy
[...]
> +    (symbol keyword boolean symbol-with-pos)
[...]
> +    (symbol-with-pos keyword))

How did you come up with `cl--type-hierarchy`?
Because, obviously, something changed here.
How is `keyword` a "direct subtype" of `symbol-with-pos`?

> +(defconst cl--direct-supertypes-of-type
> +  (make-hash-table :test #'eq)
> +  "Hash table TYPE -> SUPERTYPES.")
> +
> +(defconst cl--direct-subtypes-of-type
> +  (make-hash-table :test #'eq)
> +  "Hash table TYPE -> SUBTYPES.")
> +
> +(cl-loop for (parent . children) in cl--type-hierarchy
> +         do (cl-loop
> +             for child in children
> +             do (cl-pushnew parent (gethash child 
> cl--direct-supertypes-of-type))
> +             do (cl-pushnew child (gethash parent 
> cl--direct-subtypes-of-type))))

FWIW, I think we should create a "type descriptor" defstruct (from which
`cl--class` would inherit), and generalize the `cl--class` symbol
property to one that holds the type descriptor of the given name.

So you could get the direct parents of `integer` with something like:

    (slot-value (get 'integer 'cl--class) 'parents)

[ And then `C-h o integer RET` should show the corresponding info.  ]

> +(defconst cl--typeof-types nil

This can't make sense.
If you change it later with `push/setq` it should not be a "defconst".
So either arrange to compute its default value directly inside the
`defconst`, or use a `defvar`.

> +(maphash (lambda (type _)
> +           (push (cl--supertypes-for-typeof-types type) cl--typeof-types))
> +         cl--direct-supertypes-of-type)

Did you compare the resulting alist to the one we had before?
Remember that the order of "(direct or not) supertypes" in there is
important.
The current table has errors.  I see for example:

    (fixnum integer integer-or-marker number atom number-or-marker)

where `atom` should come *after* `number-or-marker`.


        Stefan