Handle union of different values for functions too

Closes PR 14557

original commit: b3a477d6180332a1bdc413ad3e710666df521718

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

@@ -173,9 +173,9 @@
      (tc/funapp f-stx args-stx (ret (resolve-once t) f o) argtys expected)]
     ;; a union of functions can be applied if we can apply all of the elements
     [((tc-result1: (Union: (and ts (list (Function: _) ...)))) _)
-     (ret (for/fold ([result (Un)]) ([fty (in-list ts)])
-            (match (tc/funapp f-stx args-stx (ret fty) argtys expected)
-              [(tc-result1: t) (Un result t)])))]
+     (merge-tc-results
+      (for/list ([fty ts])
+        (tc/funapp f-stx args-stx (ret fty) argtys expected)))]
     ;; error type is a perfectly good fcn type
     [((tc-result1: (Error:)) _) (ret (make-Error))]
     ;; otherwise fail

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

@@ -3007,6 +3007,20 @@
         #:ret (ret (-seq (-vec Univ)))
         #:expected (ret (-seq (-vec Univ)))]
 
+       ;; PR 14557 - apply union of functions with different return values
+       [tc-err
+        (let ()
+          (: f (U (-> Void) (-> (values Void Void))))
+          (define (f) (void))
+          (f))
+        #:msg #rx"Expected the same number of values.*1 and 2"]
+       [tc-e
+        (let ()
+          (: f (U (-> (values String Symbol)) (-> (values Void Void))))
+          (define (f) (values "foo" 'bar))
+          (f))
+        #:ret (ret (list (t:Un -String -Void) (t:Un -Symbol -Void)))]
+
         )
 
   (test-suite