[Sema] Correct IUnknown to support Unknwnbase.h Header.

Apparently, the MSVC SDK has a strange implementation that
causes a number of implicit functions as well as a template member
function of the IUnknown type. This patch allows these as InterfaceLike
types as well.

Additionally, it corrects the behavior where extern-C++ wrapped around an
Interface-Like type would permit an interface-like type to exist in a namespace.

Differential Revision: https://reviews.llvm.org/D38303

llvm-svn: 314557

1 files changed, 15 insertions, 3 deletions

diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp
index e85ab418514..a9759b4c0a2 100644
--- a/clang/lib/AST/DeclCXX.cpp
+++ b/clang/lib/AST/DeclCXX.cpp
@@ -1470,6 +1470,15 @@ bool CXXRecordDecl::isAnyDestructorNoReturn() const {
   return false;
 }
 
+static bool isDeclContextInNamespace(const DeclContext *DC) {
+  while (!DC->isTranslationUnit()) {
+    if (DC->isNamespace())
+      return true;
+    DC = DC->getParent();
+  }
+  return false;
+}
+
 bool CXXRecordDecl::isInterfaceLike() const {
   assert(hasDefinition() && "checking for interface-like without a definition");
   // All __interfaces are inheritently interface-like.
@@ -1486,13 +1495,16 @@ bool CXXRecordDecl::isInterfaceLike() const {
 
   // No interface-like type can have a method with a definition.
   for (const auto *const Method : methods())
-    if (Method->isDefined())
+    if (Method->isDefined() && !Method->isImplicit())
       return false;
 
   // Check "Special" types.
   const auto *Uuid = getAttr<UuidAttr>();
-  if (Uuid && isStruct() && (getDeclContext()->isTranslationUnit() ||
-                             getDeclContext()->isExternCXXContext()) &&
+  // MS SDK declares IUnknown/IDispatch both in the root of a TU, or in an
+  // extern C++ block directly in the TU.  These are only valid if in one
+  // of these two situations.
+  if (Uuid && isStruct() && !getDeclContext()->isExternCContext() &&
+      !isDeclContextInNamespace(getDeclContext()) &&
       ((getName() == "IUnknown" &&
         Uuid->getGuid() == "00000000-0000-0000-C000-000000000046") ||
        (getName() == "IDispatch" &&