Add type tooltip information in TR modules

This PR uses the newly added DrRacket API for communicating tooltip information to show the types of expressions in the DrRacket definitions area.
No, not really. Vectors are more convenient in this case because the syntax
property key is bringing what the prefab would bring.

On Mon, Oct 6, 2014 at 8:32 AM, Sam Tobin-Hochstadt <
notifications@github.com> wrote:

> In
> pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/types/type-table.rkt:
>
> > +              (pretty-format-type (cleanup-type type)))]
> > +        [(tc-results: types)
> > +         (apply string-append
> > +                (for/list ([(type index) (in-indexed (in-list types))])
> > +                  (format "Value ~a:~n  ~a~n"
> > +                          (add1 index)
> > +                          (pretty-format-type (cleanup-type type)
> > +                                              #:indent 2))))]
> > +        [(tc-any-results: _) "AnyValues"]))
> > +    (cond [(not printed-types) tooltips]
> > +          [(or (not (pair? (syntax-e stx)))
> > +               ;; special-case quote because there's no worry of overlap
> > +               ;; in a (quote ...) and because literals expand out to a
> > +               ;; use of quote.
> > +               (eq? (syntax-e (car (syntax-e stx))) 'quote))
> > +           (cons (vector (syntax-source stx)
>
> @rfindler <https://github.com/rfindler> Is there a reason not to make the
> expansion/check-syntax communication a prefab struct instead of a vector?
>
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> <https://github.com/plt/racket/pull/787/files#r18456205>.
>