[interop][SwiftToCxx] add a test to verify class reference can't be directly constructed from a void *

Author: hyp

test/Interop/SwiftToCxx/class/class-api-prohibited.cpp

@@ -0,0 +1,12 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %target-swift-frontend %S/swift-class-in-cxx.swift -typecheck -module-name Class -clang-header-expose-public-decls -emit-clang-header-path %t/class.h
+
+// RUN: not %target-interop-build-clangxx -c %s -I %t -o %t/swift-class-execution.o
+
+#include "class.h"
+
+void test(void * _Nonnull p) {
+  // Prohibited to construct class reference directly from opaque pointer.
+  Class::ClassWithIntField x(p);
+}