Document :type better

original commit: a40a1341f6bae61c0a8c5660182080003fae7c70

collects/typed-racket/scribblings/reference/exploring-types.scrbl

@@ -1,15 +1,37 @@
 #lang scribble/manual
 
 @begin[(require "../utils.rkt")
+       (require scribble/eval)
        (require (for-label (only-meta-in 0 [except-in typed/racket for])))]
 
+@(define the-top-eval (make-base-eval))
+@(the-top-eval '(require (except-in typed/racket #%module-begin)))
+
 @title{Exploring Types}
 
 In addition to printing a summary of the types of REPL results, Typed Racket
 provides interactive utilities to explore and query types.
 The following bindings are only available at the Typed Racket REPL.
 
-@defform[(:type t)]{Prints the type @racket[_t].}
+@defform[(:type maybe-verbose t)
+         #:grammar ([maybe-verbose (code:line)
+                                   (code:line #:verbose)])]{
+  Prints the type @racket[_t]. If @racket[_t] is a type alias
+  (e.g., @racket[Number]), then it will be expanded to its representation
+  when printing. Any further type aliases in the type named by @racket[_t]
+  will remain unexpanded.
+
+  If @racket[#:verbose] is provided, all type aliases are expanded
+  in the printed type.
+
+  @examples[#:eval the-top-eval
+    ;; I'm not sure why, but the :type examples below don't work
+    ;; without the #%top-interaction in the first example
+    (eval:alts (:type Number) (#%top-interaction . (:type Number)))
+    (:type Real)
+    (:type #:verbose Number)
+  ]
+}
 
 @defform[(:print-type e)]{Prints the type of @racket[_e]. This prints the whole
 type, which can sometimes be quite large.}
@@ -20,3 +42,6 @@ types @racket[t], shows the result type of @racket[f].}
 @defform[(:query-type/result f t)]{Given a function @racket[f] and a desired
 return type @racket[t], shows the arguments types @racket[f] should be given to
 return a value of type @racket[t].}
+
+@close-eval[the-top-eval]
+