Fix TR double cast bug

In some cases, TR tried to typecheck the contents of a quote-syntax
form that contains unexpanded syntax.

Closes PR 14355

original commit: 26204cf505f885827854908391d2842476728c8b

pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/typecheck/check-subforms-unit.rkt

@@ -9,6 +9,7 @@
          (private syntax-properties)
          (utils tc-utils)
          (for-syntax racket/base syntax/parse)
+         (for-template racket/base)
          (rep type-rep))
 
 (import tc-if^ tc-lambda^ tc-app^ tc-let^ tc-expr^)
@@ -41,7 +42,10 @@
      #'(let loop ([form init-form])
          (parameterize ([current-orig-stx form])
            (syntax-parse form
+             #:literals (quote-syntax)
              [clause bodies ...] ...
+             ;; avoid going under quote-syntax, nothing to typecheck
+             [(quote-syntax . rst) (void)]
              [(a . b)
               (loop #'a)
               (loop #'b) ]

pkgs/typed-racket-pkgs/typed-racket-test/tests/typed-racket/succeed/pr14355.rkt

@@ -0,0 +1,8 @@
+#lang typed/racket
+
+;; Test for PR 14355. Ideally would be a unit test, but
+;; the bug could not be triggered via the harness
+
+;; make sure this doesn't result in an internal error
+(cast (cast "x" String) String)
+