fix a bug in ->i parsing

collects/racket/contract/private/arr-i-parse.rkt

@@ -172,7 +172,10 @@ code does the parsing and validation of the syntax.
       (set! sp (cons from sp))
       (free-identifier-mapping-put!
        neighbors from
-       (cons to (free-identifier-mapping-get neighbors from (λ () '())))))
+       (cons to (free-identifier-mapping-get neighbors from))))
+    
+    (define (init-neighbors var)
+      (free-identifier-mapping-put! neighbors var '()))
     
     (define (no-links from)
       (set! sp (cons from sp))
@@ -182,6 +185,7 @@ code does the parsing and validation of the syntax.
       (for ([a-res (in-list arg/ress)])
         (cond
           [(arg/res-vars a-res)
+           (init-neighbors (arg/res-var a-res))
            (for ([nvar (in-list (arg/res-vars a-res))])
              (link (arg/res-var a-res) nvar))]
           [else
@@ -196,6 +200,7 @@ code does the parsing and validation of the syntax.
       (when a-rst
         (cond
           [(arg/res-vars a-rst)
+           (init-neighbors (arg/res-var a-rst))
            (for ([nvar (in-list (arg/res-vars a-rst))])
              (link (arg/res-var a-rst) nvar))]
           [else

collects/tests/racket/contract-test.rktl

@@ -3341,6 +3341,13 @@
                'neg)
      1))
   
+  ;; this used to cause a runtime error in the code that parses ->i
+  (ctest 'no-crash
+         '->i-no-vars-with-dep
+         (begin (->i ([x () any/c] [y (x) any/c]) any) 'no-crash))
+
+
+  
 ;
 ;
 ;
@@ -12854,7 +12861,7 @@ so that propagation occurs.
                                  'pos
                                  'neg))
                      (f 10)))
-
+  
 
 
 ;