Add test for memory layout

Author: junov

test/ClangImporter/Inputs/custom-modules/cxx_interop.h

@@ -39,6 +39,16 @@ int PrivateFunction() __attribute__((swift_private));
 
 class PrivateClass {} __attribute__((swift_private));
 
+class ClassWithImportedField {
+ public:
+  int field;
+};
+
+class ClassWithUnimportedField {
+ public:
+  int field __attribute__((swift_private));
+};
+
 class Methods2 {
 public:
   int SimpleMethod(int);

test/ClangImporter/cxx_interop.swift

@@ -34,4 +34,4 @@ func unimportedSwiftPrivateFunction() {
 
 func unimportedSwiftPrivateClass() {
   _ = PrivateClass() // expected-error {{cannot find 'PrivateClass' in scope}}
-}
+}

test/ClangImporter/cxx_interop_layout.swift

@@ -0,0 +1,8 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-build-swift -Xfrontend -cxx-interoperability-mode=default -I %S/Inputs/custom-modules %s -o %t/a.out
+// RUN: %target-run %t/a.out
+
+import CXXInterop
+
+assert(MemoryLayout<ClassWithImportedField>.size == MemoryLayout<ClassWithUnimportedField>.size,
+  "ClassWithImportedField and ClassWithUnimportedField should have the same size.")