Add #:omit-define-syntaxes to define-type.

original commit: ecf02a32b4e2431e57f77da4f497fcb8f62426ec

collects/tests/typed-racket/succeed/define-type-omit-define.rkt

@@ -0,0 +1,9 @@
+#lang typed/racket
+
+(define-syntax (x stx) #'5)
+
+(define-type x Number #:omit-define-syntaxes)
+
+(ann 7 x)
+
+(add1 x)

collects/typed-racket/base-env/prims.rkt

@@ -450,9 +450,13 @@ This file defines two sorts of primitives. All of them are provided into any mod
 
 (define-syntax (define-type-alias stx)
   (syntax-parse stx
-    [(_ tname:id rest)
+    [(_ tname:id rest (~optional (~and omit #:omit-define-syntaxes)
+                                 #:defaults
+                                 ([omit #f])))
      #`(begin
-         #,(ignore #'(define-syntax tname (lambda (stx) (raise-syntax-error 'type-check "type name used out of context" stx))))
+         #,(if (not (attribute omit))
+               (ignore #'(define-syntax tname (lambda (stx) (raise-syntax-error 'type-check "type name used out of context" stx))))
+               #'(begin))
          #,(internal (syntax/loc stx (define-type-alias-internal tname rest))))]
     [(_ (tname:id args:id ...) rest)
      (syntax/loc stx (define-type-alias tname (All (args ...) rest)))]))

collects/typed-racket/scribblings/reference/special-forms.scrbl

@@ -285,8 +285,10 @@ corresponding to @racket[define-struct].}
  The procdure @racket[e] is used as the value for @racket[prop:procedure], and must have type @racket[proc-t].}
 
 @section{Names for Types}
-@defform*[[(define-type name t)
-           (define-type (name v ...) t)]]{
+@defform*[[(define-type name t maybe-omit-def)
+           (define-type (name v ...) t maybe-omit-def)]
+          #:grammar
+          [(maybe-omit-def (code:line #:omit-define-syntaxes) (code:line))]]{
 The first form defines @racket[name] as type, with the same meaning as
 @racket[t].  The second form is equivalent to
 @racket[(define-type name (All (v ...) t))].  Type names may
@@ -294,7 +296,11 @@ refer to other types defined in the same module, but
 cycles among them are prohibited.
 
 @ex[(define-type IntStr (U Integer String))
-    (define-type (ListofPairs A) (Listof (Pair A A)))]}
+    (define-type (ListofPairs A) (Listof (Pair A A)))]
+
+If @racket[#:omit-define-syntaxes] is specified, no definition of
+@racket[name] is created. In this case, some other definition of @racket[name]
+is necessary.}
 
 @section{Generating Predicates Automatically}