Make resolve actually do all the necessary resolutions.

original commit: 84d3051feeaca7451c8bfc7f8e0f7abad7475830

collects/tests/typed-racket/succeed/struct-top-recursive.rkt

@@ -0,0 +1,6 @@
+#lang typed/racket/base
+
+(struct: (v) a ((x : v)) #:mutable)
+
+(: z (Struct (Rec b (a (U #f b)))))
+(define z (a #f))

collects/typed-racket/types/resolve.rkt

@@ -86,7 +86,14 @@
           (hash-set! resolver-cache seq r*))
         r*)))
 
+
+;; Repeatedly unfolds Mu, App, and Name constructors until the top type
+;; constructor is not one of them.
+;; Type/c? -> Type/c?
 (define (resolve t)
-  (if (needs-resolving? t) (resolve-once t) t))
+  (let loop ((t t))
+    (if (needs-resolving? t)
+        (loop (resolve-once t))
+        t)))
 
 ;(trace resolve-app)