improve handling with-handlers (#1036)

closes #1028

Author: capfredf

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

@@ -68,11 +68,13 @@
          (loop (instantiate-poly t (map (λ (n) Univ) ns)))]
         ;; This clause should raise an error via the check-below test
         [_
-         (cond [;; a redundant test, but it ensures an error message below
-                (not (subtype t (-> prop-type Univ)))
-                (parameterize ([current-orig-stx stx])
-                  (check-below t (-> prop-type Univ)))]
-               [else (int-err "get-range-result: should not happen. type ~a prop ~a"
+         (cond
+           [(subtype t -Bottom)]
+           [;; a redundant test, but it ensures an error message below
+            (not (subtype t (-> prop-type Univ)))
+            (parameterize ([current-orig-stx stx])
+              (check-below t (-> prop-type Univ)))]
+           [else (int-err "get-range-result: should not happen. type ~a prop ~a"
                               t prop-type)])
          (ret (Un))])))
 

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

@@ -3673,6 +3673,13 @@
                         [symbol? (lambda (x) (symbol->string x))])
           (raise 'foo))
         #:ret (tc-ret -String)]
+       [tc-err
+        (with-handlers ([exn:fail? (values #f #f)]) (values #t #t))
+        #:ret (tc-ret (list -True -True))
+        #:msg #rx"expected single value, got multiple"]
+       [tc-e
+        (with-handlers ([exn:fail? (error 'hi "error")]) #t)
+        -True]
 
        [tc-err
         (raise (λ ([x : Number]) (add1 x)))]