1 files changed, 99 insertions, 0 deletions
diff --git a/include/clang/AST/TemplateArgumentVisitor.h b/include/clang/AST/TemplateArgumentVisitor.h
new file mode 100644
index 000000000000..e1cc392a1705
--- /dev/null
+++ b/include/clang/AST/TemplateArgumentVisitor.h
@@ -0,0 +1,99 @@
+//===- TemplateArgumentVisitor.h - Visitor for TArg subclasses --*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines the TemplateArgumentVisitor interface.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_AST_TEMPLATEARGUMENTVISITOR_H
+#define LLVM_CLANG_AST_TEMPLATEARGUMENTVISITOR_H
+
+#include "clang/AST/TemplateBase.h"
+
+namespace clang {
+
+namespace templateargumentvisitor {
+
+/// A simple visitor class that helps create template argument visitors.
+template <template <typename> class Ref, typename ImplClass,
+          typename RetTy = void, typename... ParamTys>
+class Base {
+public:
+#define REF(CLASS) typename Ref<CLASS>::type
+#define DISPATCH(NAME)                                                         \
+  case TemplateArgument::NAME:                                                 \
+    return static_cast<ImplClass *>(this)->Visit##NAME##TemplateArgument(      \
+        TA, std::forward<ParamTys>(P)...)
+
+  RetTy Visit(REF(TemplateArgument) TA, ParamTys... P) {
+    switch (TA.getKind()) {
+      DISPATCH(Null);
+      DISPATCH(Type);
+      DISPATCH(Declaration);
+      DISPATCH(NullPtr);
+      DISPATCH(Integral);
+      DISPATCH(Template);
+      DISPATCH(TemplateExpansion);
+      DISPATCH(Expression);
+      DISPATCH(Pack);
+    }
+    llvm_unreachable("TemplateArgument is not covered in switch!");
+  }
+
+  // If the implementation chooses not to implement a certain visit
+  // method, fall back to the parent.
+
+#define VISIT_METHOD(CATEGORY)                                                 \
+  RetTy Visit##CATEGORY##TemplateArgument(REF(TemplateArgument) TA,            \
+                                          ParamTys... P) {                     \
+    return VisitTemplateArgument(TA, std::forward<ParamTys>(P)...);            \
+  }
+
+  VISIT_METHOD(Null);
+  VISIT_METHOD(Type);
+  VISIT_METHOD(Declaration);
+  VISIT_METHOD(NullPtr);
+  VISIT_METHOD(Integral);
+  VISIT_METHOD(Template);
+  VISIT_METHOD(TemplateExpansion);
+  VISIT_METHOD(Expression);
+  VISIT_METHOD(Pack);
+
+  RetTy VisitTemplateArgument(REF(TemplateArgument), ParamTys...) {
+    return RetTy();
+  }
+
+#undef REF
+#undef DISPATCH
+#undef VISIT_METHOD
+};
+
+} // namespace templateargumentvisitor
+
+/// A simple visitor class that helps create template argument visitors.
+///
+/// This class does not preserve constness of TemplateArgument references (see
+/// also ConstTemplateArgumentVisitor).
+template <typename ImplClass, typename RetTy = void, typename... ParamTys>
+class TemplateArgumentVisitor
+    : public templateargumentvisitor::Base<std::add_lvalue_reference, ImplClass,
+                                           RetTy, ParamTys...> {};
+
+/// A simple visitor class that helps create template argument visitors.
+///
+/// This class preserves constness of TemplateArgument references (see also
+/// TemplateArgumentVisitor).
+template <typename ImplClass, typename RetTy = void, typename... ParamTys>
+class ConstTemplateArgumentVisitor
+    : public templateargumentvisitor::Base<llvm::make_const_ref, ImplClass,
+                                           RetTy, ParamTys...> {};
+
+} // namespace clang
+
+#endif // LLVM_CLANG_AST_TEMPLATEARGUMENTVISITOR_H