Add define: form variant for polymorphic non-function values

original commit: acda049f7d102bd370d750e524e8fd7638201627

collects/tests/typed-racket/succeed/define-poly-value.rkt

@@ -0,0 +1,6 @@
+#lang typed/racket
+
+;; Test the define: non-function form
+
+(define: (a) x : (Sequenceof a) empty-sequence)
+(define: (a) f : (Integer a -> (Vectorof a)) make-vector)

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

@@ -370,6 +370,12 @@ This file defines two sorts of primitives. All of them are provided into any mod
      (identifier? #'nm)
      (with-syntax ([new-nm (syntax-property #'nm 'type-label #'ty)])
        (syntax/loc stx (define new-nm body)))]
+    [(define: (tvars:id ...) nm:id : ty body)
+     (with-syntax ([type (syntax/loc #'ty (All (tvars ...) ty))])
+       (syntax/loc stx
+         (begin
+           (: nm : type)
+           (define nm body))))]
     [(define: (tvars:id ...) (nm:id . formals:annotated-formals) : ret-ty body ...)
      (with-syntax ([type (syntax/loc #'ret-ty (All (tvars ...) (formals.arg-ty ... -> ret-ty)))])
        (syntax/loc stx

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

@@ -229,11 +229,13 @@ annotations are optional.
 
 @defform*[[(define: v : t e)
            (define: (f . formals) : t . body)
+           (define: (a ...) v : t e)
            (define: (a ...) (f . formals) : t . body)]]{
 These forms define variables, with annotated types.  The first form
-defines @racket[v] with type @racket[t] and value @racket[e].  The
-second and third forms defines a function @racket[f] with appropriate
-types.  In most cases, use of @racket[:] is preferred to use of @racket[define:].
+defines @racket[v] with type @racket[t] and value @racket[e]. The third
+form does the same, but allows the specification of type variables.
+The second and fourth forms defines a function @racket[f] with appropriate
+types. In most cases, use of @racket[:] is preferred to use of @racket[define:].
 
 @ex[(define: foo : Integer 10)
 
@@ -241,6 +243,8 @@ types.  In most cases, use of @racket[:] is preferred to use of @racket[define:]
                   [rest  : Integer]) : Integer
       (+ first rest))
 
+    (define: (A) mt-seq : (Sequenceof A) empty-sequence)
+
     (define: (A) (poly-app [func : (A A -> A)]
                            [first : A]
                            [rest  : A]) : A