diff --git a/collects/racket/contract/private/arr-i-parse.rkt b/collects/racket/contract/private/arr-i-parse.rkt
new file mode 100644
index 0000000000..7d785fb569
--- /dev/null
+++ b/collects/racket/contract/private/arr-i-parse.rkt
@@ -0,0 +1,114 @@
+#lang racket/base
+#|
+
+The ->i contract first parses its input into an istx struct 
+and then operates on it to generate the expanded form
+
+|#
+
+;; doms : (listof arg?)
+;; pre  : (or/c stx[expr] #f)
+;; rngs : (listof res?)
+;; rest : (or/c #f rst?)
+;; post : (or/c stx[expr] #f)
+(define-struct istx (doms pre rngs rest post))
+
+;; var  : identifier?
+;; vars : (or/c #f (listof identifier?))
+;; ctc  : syntax[expr]
+(define-struct res (var vars ctc))
+
+;; kwd  : (or/c #f syntax[kwd])
+;; var  : identifier?
+;; vars : (or/c #f (listof identifier?))
+;; optional? : boolean?
+;; ctc  : syntax[expr]
+(define-struct arg (kwd var vars optional? ctc))
+
+;; var  : identifier?
+;; vars : (or/c #f (listof identifier?))
+;; ctc  : syntax[expr]
+(define-struct rst (var vars ctc))
+
+(define (parse-->i stx)
+  (let-values ([(raw-mandatory-doms raw-optional-doms id/rest-id pre-cond range post-cond)
+                (pull-out-pieces stx)])
+    (make-istx (append (map parse-dom raw-mandatory-doms)
+                       (map parse-dom raw-optional-doms))
+               pre-cond
+               range
+               rest
+               post)))
+
+;; pull-out-pieces : stx -> (values raw-mandatory-doms raw-optional-doms id/rest-id pre-cond range post-cond) 
+(define (pull-out-pieces stx)
+  (let*-values ([(raw-mandatory-doms leftover) 
+                 (syntax-case stx ()
+                   [((raw-mandatory-doms ...) . leftover)
+                    (values (syntax->list #'(raw-mandatory-doms ...)) 
+                            #'leftover)]
+                   [(a . leftover)
+                    (raise-syntax-error #f "expected a sequence of mandatory domain elements" stx #'a)]
+                   [_
+                    (raise-syntax-error #f "expected a sequence of mandatory domain elements" stx)])]
+                [(raw-optional-doms leftover)
+                 (syntax-case leftover ()
+                   [(kwd . leftover2)
+                    (keyword? (syntax-e #'kwd))
+                    (values '() leftover)]
+                   [(dep-range)
+                    (values '() leftover)]
+                   [(dep-range #:post-cond expr)
+                    (values '() leftover)]
+                   [((opts ...) . rest)
+                    (values #'(opts ...) #'rest)]
+                   [_ (values '() leftover)])]
+                [(id/rest-id leftover) 
+                 (syntax-case leftover ()
+                   [(#:rest id rest-expr . leftover)
+                    (and (identifier? #'id)
+                         (not (keyword? (syntax-e #'rest-expr))))
+                    (values #'(id rest-expr) #'leftover)]
+                   [(#:rest id (id2 ...) rest-expr . leftover)
+                    (and (identifier? #'id)
+                         (andmap identifier? (syntax->list #'(id2 ...)))
+                         (not (keyword? (syntax-e #'rest-expr))))
+                    (values #'(id rest-expr) #'leftover)]
+                   [(#:rest id rest-expr . leftover)
+                    (begin
+                      (unless (identifier? #'id)
+                        (raise-syntax-error #f "expected an identifier" stx #'id))
+                      (when (keyword? (syntax-e #'rest-expr))
+                        (raise-syntax-error #f "expected an expression, not a keyword" stx #'rest-expr)))]
+                   [_ (values #f leftover)])]
+                [(pre-cond leftover)
+                 (syntax-case leftover ()
+                   [(#:pre-cond pre-cond . leftover)
+                    (values #'pre-cond #'leftover)]
+                   [_ (values #f leftover)])]
+                [(range leftover) 
+                 (syntax-case leftover ()
+                   [(range . leftover) (values #'range #'leftover)]
+                   [_
+                    (raise-syntax-error #f "expected a range expression, but found nothing" stx)])]
+                [(post-cond leftover) 
+                 (syntax-case leftover ()
+                   [(#:post-cond post-cond . leftover)
+                    (begin
+                      (syntax-case range (any)
+                        [any (raise-syntax-error #f "cannot have a #:post-cond with any as the range" stx #'post-cond)]
+                        [_ (void)])
+                      (values #'post-cond #'leftover))]
+                   [_ (values #f leftover)])])
+    (syntax-case leftover ()
+      [() 
+       (values raw-mandatory-doms raw-optional-doms id/rest-id pre-cond range post-cond)]
+      [_ 
+       (raise-syntax-error #f "bad syntax" stx)])))
+
+(provide
+ parse-->i
+ (struct-out istx)
+ (struct-out res)
+ (struct-out arg)
+ (struct-out rst))
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