Fix new error messages for class/object types

Closes PR 14942

typed-racket-lib/typed-racket/typecheck/error-message.rkt

@@ -53,10 +53,8 @@
                     "type variables bound in different scopes")]
     [((? Class?) (? Class?))
      (class-mismatch r1 r2)]
-    [((Instance: c1) (Instance: c2))
-     (define r1 (resolve c1))
-     (define r2 (resolve c2))
-     (class-mismatch r1 r2 #t)]
+    [((Instance: (app resolve (? Class? c1))) (Instance: (app resolve (? Class? c2))))
+     (class-mismatch c1 c2 #t)]
     ;; Don't call this with resolved types since we may want to print
     ;; the type alias name instead of the actual type
     [(_ _) (type-mismatch t1 t2)]))

typed-racket-lib/typed-racket/types/printer.rkt

@@ -498,6 +498,7 @@
     [(Syntax: t) `(Syntaxof ,(t->s t))]
     [(Instance: (and (? has-name?) cls)) `(Instance ,(t->s cls))]
     [(Instance: (? Class? cls)) (class->sexp cls #:object? #t)]
+    [(Instance: t) `(Instance ,(t->s t))] ; for cases like Error
     [(ClassTop:) 'ClassTop]
     [(? Class?) (class->sexp type)]
     [(Result: t (or (NoFilter:) (FilterSet: (Top:) (Top:))) (or (NoObject:) (Empty:))) (type->sexp t)]

typed-racket-test/unit-tests/class-tests.rkt

@@ -1792,4 +1792,12 @@
              (ann (class object% (super-new) (init-rest [rst : (Listof String)]))
                   (Class (init-rest (Listof Void))))
              (error "foo"))
-           #:msg #rx"expected: \\(Listof Void\\).*given: \\(Listof String\\)"]))
+           #:msg #rx"expected: \\(Listof Void\\).*given: \\(Listof String\\)"]
+   ;; PR 14942
+   [tc-err (let ()
+             (: x (Instance BadAlias))
+             (define x (error "foo"))
+             (: y (Object (field [x Any])))
+             (define y x)
+             (error "foo"))
+           #:msg "parse error in type"]))