ATRONIX: Type-check call of TRY/except handler

TRY/except now checks that the typespec of a handler function actually
allows calls with the error value, before calling the handler function.

This fixes CureCode issue #1514.

metaeducation/rebol-issues#1514

Author: Oldes

src/core/n-control.c

@@ -777,6 +777,14 @@ enum {
 			}
 			else { // do func[err] error
 				REBVAL error = *DS_NEXT; // will get overwritten
+				REBVAL *args = BLK_SKIP(VAL_FUNC_ARGS(&handler), 1);
+				if (NOT_END(args) && !TYPE_CHECK(args, VAL_TYPE(&error))) {
+					// TODO: This results in an error message such as "action!
+					// does not allow error! for its value1 argument". A better
+					// message would be more like "except handler does not
+					// allow error! for its value1 argument."
+					Trap3(RE_EXPECT_ARG, Of_Type(&handler), args, Of_Type(&error));
+				}
 				Apply_Func(0, &handler, &error, 0);
 			}
 		}