Index: lldb/trunk/include/lldb/Symbol/DeclVendor.h
===================================================================
--- lldb/trunk/include/lldb/Symbol/DeclVendor.h
+++ lldb/trunk/include/lldb/Symbol/DeclVendor.h
@@ -12,8 +12,6 @@
 #include "lldb/Core/ClangForward.h"
 #include "lldb/lldb-defines.h"
 
-#include "clang/AST/ExternalASTMerger.h"
-
 #include <vector>
 
 namespace lldb_private {
@@ -22,11 +20,19 @@
 // declarations that are not necessarily backed by a specific symbol file.
 class DeclVendor {
 public:
+  enum DeclVendorKind {
+    eClangDeclVendor,
+    eClangModuleDeclVendor,
+    eAppleObjCDeclVendor,
+    eLastClangDeclVendor,
+  };
   // Constructors and Destructors
-  DeclVendor() {}
+  DeclVendor(DeclVendorKind kind) : m_kind(kind) {}
 
   virtual ~DeclVendor() {}
 
+  DeclVendorKind GetKind() const { return m_kind; }
+
   /// Look up the set of Decls that the DeclVendor currently knows about
   /// matching a given name.
   ///
@@ -60,16 +66,11 @@
   ///     The vector of CompilerTypes that was found.
   std::vector<CompilerType> FindTypes(ConstString name, uint32_t max_matches);
 
-  /// Interface for ExternalASTMerger.  Returns an ImporterSource 
-  /// allowing type completion.
-  ///
-  /// \return
-  ///     An ImporterSource for this DeclVendor.
-  virtual clang::ExternalASTMerger::ImporterSource GetImporterSource() = 0;
-
 private:
   // For DeclVendor only
   DISALLOW_COPY_AND_ASSIGN(DeclVendor);
+
+  const DeclVendorKind m_kind;
 };
 
 } // namespace lldb_private
Index: lldb/trunk/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp
===================================================================
--- lldb/trunk/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp
+++ lldb/trunk/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp
@@ -100,17 +100,15 @@
       if (!language_runtime)
         break;
 
-      DeclVendor *runtime_decl_vendor = language_runtime->GetDeclVendor();
-
-      if (!runtime_decl_vendor)
-        break;
-
-      sources.push_back(runtime_decl_vendor->GetImporterSource());
+      if (auto *runtime_decl_vendor = llvm::dyn_cast_or_null<ClangDeclVendor>(
+              language_runtime->GetDeclVendor())) {
+        sources.push_back(runtime_decl_vendor->GetImporterSource());
+      }
     } while (false);
 
     do {
-      DeclVendor *modules_decl_vendor =
-          m_target->GetClangModulesDeclVendor();
+      auto *modules_decl_vendor = llvm::cast<ClangModulesDeclVendor>(
+          m_target->GetClangModulesDeclVendor());
 
       if (!modules_decl_vendor)
         break;
Index: lldb/trunk/source/Plugins/ExpressionParser/Clang/ClangDeclVendor.h
===================================================================
--- lldb/trunk/source/Plugins/ExpressionParser/Clang/ClangDeclVendor.h
+++ lldb/trunk/source/Plugins/ExpressionParser/Clang/ClangDeclVendor.h
@@ -0,0 +1,42 @@
+//===-- ClangDeclVendor.h ---------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef liblldb_ClangDeclVendor_h_
+#define liblldb_ClangDeclVendor_h_
+
+#include "lldb/Symbol/DeclVendor.h"
+
+#include "clang/AST/ExternalASTMerger.h"
+
+namespace lldb_private {
+
+// A clang specialized extension to DeclVendor.
+class ClangDeclVendor : public DeclVendor {
+public:
+  ClangDeclVendor(DeclVendorKind kind) : DeclVendor(kind) {}
+
+  virtual ~ClangDeclVendor() {}
+
+  /// Interface for ExternalASTMerger. Returns an ImporterSource allowing type
+  /// completion.
+  ///
+  /// \return
+  ///     An ImporterSource for this ClangDeclVendor.
+  virtual clang::ExternalASTMerger::ImporterSource GetImporterSource() = 0;
+
+  static bool classof(const DeclVendor *vendor) {
+    return vendor->GetKind() >= eClangDeclVendor &&
+           vendor->GetKind() < eLastClangDeclVendor;
+  }
+
+private:
+  DISALLOW_COPY_AND_ASSIGN(ClangDeclVendor);
+};
+}; // namespace lldb_private
+
+#endif
Index: lldb/trunk/source/Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.h
===================================================================
--- lldb/trunk/source/Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.h
+++ lldb/trunk/source/Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.h
@@ -10,22 +10,27 @@
 #define liblldb_ClangModulesDeclVendor_h
 
 #include "lldb/Core/ClangForward.h"
-#include "lldb/Symbol/DeclVendor.h"
 #include "lldb/Symbol/SourceModule.h"
 #include "lldb/Target/Platform.h"
 
+#include "Plugins/ExpressionParser/Clang/ClangDeclVendor.h"
+
 #include <set>
 #include <vector>
 
 namespace lldb_private {
 
-class ClangModulesDeclVendor : public DeclVendor {
+class ClangModulesDeclVendor : public ClangDeclVendor {
 public:
   // Constructors and Destructors
   ClangModulesDeclVendor();
 
   ~ClangModulesDeclVendor() override;
 
+  static bool classof(const DeclVendor *vendor) {
+    return vendor->GetKind() == eClangModuleDeclVendor;
+  }
+
   static ClangModulesDeclVendor *Create(Target &target);
 
   typedef std::vector<ConstString> ModulePath;
Index: lldb/trunk/source/Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.cpp
===================================================================
--- lldb/trunk/source/Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.cpp
+++ lldb/trunk/source/Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.cpp
@@ -147,7 +147,8 @@
   }
 }
 
-ClangModulesDeclVendor::ClangModulesDeclVendor() {}
+ClangModulesDeclVendor::ClangModulesDeclVendor()
+    : ClangDeclVendor(eClangModuleDeclVendor) {}
 
 ClangModulesDeclVendor::~ClangModulesDeclVendor() {}
 
Index: lldb/trunk/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCDeclVendor.h
===================================================================
--- lldb/trunk/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCDeclVendor.h
+++ lldb/trunk/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCDeclVendor.h
@@ -10,19 +10,23 @@
 #define liblldb_AppleObjCDeclVendor_h_
 
 #include "lldb/Symbol/ClangASTContext.h"
-#include "lldb/Symbol/DeclVendor.h"
 #include "lldb/lldb-private.h"
 
+#include "Plugins/ExpressionParser/Clang/ClangDeclVendor.h"
 #include "Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.h"
 
 namespace lldb_private {
 
 class AppleObjCExternalASTSource;
 
-class AppleObjCDeclVendor : public DeclVendor {
+class AppleObjCDeclVendor : public ClangDeclVendor {
 public:
   AppleObjCDeclVendor(ObjCLanguageRuntime &runtime);
 
+  static bool classof(const DeclVendor *vendor) {
+    return vendor->GetKind() == eAppleObjCDeclVendor;
+  }
+
   uint32_t FindDecls(ConstString name, bool append, uint32_t max_matches,
                      std::vector<clang::NamedDecl *> &decls) override;
 
Index: lldb/trunk/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCDeclVendor.cpp
===================================================================
--- lldb/trunk/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCDeclVendor.cpp
+++ lldb/trunk/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCDeclVendor.cpp
@@ -151,12 +151,13 @@
 };
 
 AppleObjCDeclVendor::AppleObjCDeclVendor(ObjCLanguageRuntime &runtime)
-    : DeclVendor(), m_runtime(runtime), m_ast_ctx(runtime.GetProcess()
-                                                      ->GetTarget()
-                                                      .GetArchitecture()
-                                                      .GetTriple()
-                                                      .getTriple()
-                                                      .c_str()),
+    : ClangDeclVendor(eAppleObjCDeclVendor), m_runtime(runtime),
+      m_ast_ctx(runtime.GetProcess()
+                    ->GetTarget()
+                    .GetArchitecture()
+                    .GetTriple()
+                    .getTriple()
+                    .c_str()),
       m_type_realizer_sp(m_runtime.GetEncodingToType()) {
   m_external_source = new AppleObjCExternalASTSource(*this);
   llvm::IntrusiveRefCntPtr<clang::ExternalASTSource> external_source_owning_ptr(