Remove bogus reference to 'sexpression', add docs for Sexp type, don't use Sexp where inappropriate

original commit: 26e73cf61d80636246dd0bf5912b7670c30698d6

collects/typed-scheme/private/base-env.rkt

@@ -190,7 +190,7 @@
                            'must-truncate 'truncate/replace)
         #f
         -Output-Port)]
-[read (->opt [-Input-Port] (Un -Sexp (-val eof)))]
+[read (->opt [-Input-Port] Univ)]
 [ormap (-polydots (a c b) (->... (list (->... (list a) (b b) c) (-lst a)) ((-lst b) b) c))]
 [andmap (-polydots (a c d b) (cl->*
                               ;; 1 means predicate on second argument
@@ -616,11 +616,11 @@
 [delete-file (-> -Pathlike -Void)]
 [make-namespace (->opt [(Un (-val 'empty) (-val 'initial))] -Namespace)]
 [make-base-namespace (-> -Namespace)]
-[eval (-> -Sexp Univ)]
+[eval (->opt Univ [-Namespace] Univ)]
 
 [exit (-> (Un))]
 
-[module->namespace (-> -Sexp -Namespace)]
+[module->namespace (-> (-mu x (-lst (Un -Symbol -String -Nat x (-val #f)))) -Namespace)]
 [current-namespace (-Param -Namespace -Namespace)]
 
 [getenv (-> -String (Un -String (-val #f)))]

collects/typed-scheme/scribblings/ts-reference.scrbl

@@ -178,6 +178,10 @@ corresponding to @racket[trest], where @racket[bound]
 @defform[(Promise t)]{A @rtech{promise} of @racket[t].
  @ex[(delay 3)]}
 
+@defidform[Sexp]{A recursive union containing types traversed by
+@racket[datum->syntax]. Note that this is @emph{not} the type produced
+by @racket[read].} 
+
 @subsection{Other Type Constructors}
 
 @defform*[#:id -> #:literals (* ...)

collects/typed-scheme/scribblings/types.scrbl

@@ -148,7 +148,7 @@ Typed Racket offers abstraction over types as well as values.
 
 @subsection{Polymorphic Data Structures}
 
-Virtually every Racket program uses lists and sexpressions.  Fortunately, Typed
+Virtually every Racket program uses lists and other collections.  Fortunately, Typed
 Racket can handle these as well.  A simple list processing program can be
 written like this: