Add one-sided contract for ClassTop types

Closes PR 14486

original commit: 8b245240ea41630905b5a66eb76485a15c113b7a

pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/private/type-contract.rkt

@@ -335,6 +335,7 @@
         [(ThreadCellTop:) (only-untyped thread-cell?/sc)]
         [(Prompt-TagTop:) (only-untyped prompt-tag?/sc)]
         [(Continuation-Mark-KeyTop:) (only-untyped continuation-mark-key?/sc)]
+        [(ClassTop:) (only-untyped class?/sc)]
         ;; TODO Figure out how this should work
         ;[(StructTop: s) (struct-top/sc s)]
 

pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/static-contracts/combinators/derived.rkt

@@ -5,7 +5,8 @@
 ;; Ex: (listof/sc any/sc) => list?/sc
 
 (require "simple.rkt" "structural.rkt"
-         (for-template racket/base racket/list racket/set racket/promise racket/mpair))
+         (for-template racket/base racket/list racket/set racket/promise racket/mpair
+                       racket/class))
 (provide (all-defined-out))
 
 (define identifier?/sc (flat/sc #'identifier?))
@@ -30,3 +31,5 @@
 (define thread-cell?/sc (flat/sc #'thread-cell?))
 (define prompt-tag?/sc (flat/sc #'continuation-prompt-tag?))
 (define continuation-mark-key?/sc (flat/sc #'continuation-mark-key?))
+
+(define class?/sc (flat/sc #'class?))

pkgs/typed-racket-pkgs/typed-racket-test/tests/typed-racket/succeed/make-top-predicate.rkt

@@ -8,6 +8,7 @@
 (make-predicate Thread-CellTop)
 (make-predicate Prompt-TagTop)
 (make-predicate Continuation-Mark-KeyTop)
+(make-predicate ClassTop)