Fix misuse of expected in tc-funapp.

original commit: eaafd418d977dd77507b56b6cd8e9f0db4fcc5b6

pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/typecheck/tc-funapp.rkt

@@ -53,7 +53,7 @@
       ;; if nothing matched, error
       (domain-mismatches
        f-stx args-stx t doms rests drests rngs argtys #f #f
-       #:expected expected #:return (if (tc-results? expected) expected (ret (Un)))
+       #:expected expected #:return (ret (Un))
        #:msg-thunk (lambda (dom)
                      (string-append
                       "No function domains matched in function application:\n"

pkgs/typed-racket-pkgs/typed-racket-test/tests/typed-racket/unit-tests/typecheck-tests.rkt

@@ -2679,6 +2679,15 @@
            4)
          -PosByte]
 
+       [tc-err
+         (let ()
+           (: z (case-> (Symbol -> Symbol)
+                        (Number -> Number)))
+           (define z (lambda (a) a))
+           (z "y"))
+         #:ret (ret -String)
+         #:expected (ret -String -no-filter -no-obj)]
+
         )
   (test-suite
    "tc-literal tests"