racket/class: fix serialization with class contracts

Closes #1589

pkgs/racket-test-core/tests/racket/serialize.rktl

@@ -510,6 +510,27 @@
 (test #t pair? (serialize (new s:bad% [foo 10])))
 (err/rt-test (deserialize (serialize (new s:bad% [foo 10]))) exn:fail:object?)
 
+;; ----------------------------------------
+;; Class contracts & serialization
+
+(define class+contract+serialize-foo<%>
+  (interface ()
+    [foo-method (->m any/c)]))
+(define-serializable-class* class+contract+serialize-foo% object% (class+contract+serialize-foo<%>)
+  (inspect #f)
+  (init-field [v #hasheq()])
+  (define/public (foo-method)
+    'result)
+  (super-new))
+
+(let ()
+  (define inst
+    (new class+contract+serialize-foo%))
+
+  (test #t is-a? inst class+contract+serialize-foo%)
+  (test #t is-a? (deserialize (serialize inst)) class+contract+serialize-foo%)
+  (test 'result values (send (deserialize (serialize inst)) foo-method)))
+
 ;; ----------------------------------------
 
 ;; Custom deserialize:

racket/collects/racket/private/class-internal.rkt

@@ -2808,7 +2808,7 @@ last few projections.
                                            (send o internalize args)
                                            o))
                                        (lambda (args)
-                                         (let ([o (object-make)])
+                                         (let ([o (make-object-uninitialized c `(class ,name))])
                                            ((class-fixup c) o args)
                                            o)))
                                    (if (interface-extension? i externalizable<%>)
@@ -3547,6 +3547,9 @@ An example
     (define neg-blame (cadddr info))
     (contract ctc meth pos-blame neg-blame m #f)))
 
+(define (make-object-uninitialized class blame)
+  (do-make-object blame class 'uninit 'uninit))
+
 (define (do-make-object blame class by-pos-args named-args)
   (cond
     [(impersonator-prop:has-wrapped-class-neg-party? class)
@@ -3585,8 +3588,9 @@ An example
   ;; Generate correct class by concretizing methods w/interface ctcs
   (define concrete-class (fetch-concrete-class class blame))
   (define o ((class-make-object concrete-class)))
+  (unless (eq? by-pos-args 'uninit)
     (continue-make-object o concrete-class by-pos-args named-args #t
-                        wrapped-blame wrapped-neg-party init-proj-pairs)
+                          wrapped-blame wrapped-neg-party init-proj-pairs))
   o)
 
 (define (get-field-alist obj)