doc repairs

collects/games/cards/cards.scrbl

@@ -97,7 +97,6 @@ Returns a region like one made by @scheme[make-region], but the is
                                  [y real?]
                                  [w (and/c real? (not/c negative?))]
                                  [h (and/c real? (not/c negative?))]
-                                 [label (or/c string? false/c)]
                                  [paint-callback
                                   ((is-a?/c dc<%>) real? real? real? real? . -> . any)])
          region?]{

collects/scribblings/reference/printer.scrbl

@@ -238,7 +238,8 @@ for which the structure is an instance:
 
  @item{If the structure has a @scheme[prop:custom-write] property
        value, then the associated procedure is used to print the
-       structure.}
+       structure, unless the @racket[print-unreadable] parameter is
+       set to @racket[#f].}
 
  @item{If the structure type is transparent, or if any ancestor is
        transparent, then the structure prints as the vector produced
@@ -335,7 +336,10 @@ starting with @litchar{#px} (for @scheme[pregexp]-based regexps) or
 
 @section[#:tag "print-unreadable"]{Printing Unreadable Values}
 
-For any value with no other printing specification, the output form is
-@litchar{#<}@nonterm{something}@litchar{>}, where @nonterm{something}
-is specific to the type of the value and sometimes to the value
-itself.
+For any value with no other printing specification, assuming that the
+@racket[print-unreadable] parameter is set to @racket[#t], the output
+form is @litchar{#<}@nonterm{something}@litchar{>}, where
+@nonterm{something} is specific to the type of the value and sometimes
+to the value itself. If @racket[print-unreadable] is set to
+@racket[#f], then attempting to print an unreadable value raises
+@racket[exn:fail].

collects/scribblings/reference/write.scrbl

@@ -163,13 +163,15 @@ mutable pairs print using @litchar["{"] and @litchar["}"] instead of
 
 @defboolparam[print-unreadable on?]{
 
-A parameter that controls printing values that have no
+A parameter that enables or disables printing of values that have no
 @racket[read]able form (using the default reader), including
 structures that have a custom-write procedure (see
 @racket[prop:custom-write]), but not including @tech{uninterned}
 symbols and @tech{unreadable symbols} (which print the same as
-@tech{interned} symbols); defaults to @racket[#t]. See
-@secref["printing"] for more information.}
+@tech{interned} symbols). If the parameter value is @racket[#f], an
+attempt to print an unreadable value raises @racket[exn:fail]. The
+parameter value defaults to @racket[#t]. See @secref["printing"] for
+more information.}
 
 @defboolparam[print-graph on?]{