4 files changed, 70 insertions, 0 deletions
diff --git a/include/clang/AST/ExprCXX.h b/include/clang/AST/ExprCXX.h
index eca0ff9379..0c4ca8e979 100644
--- a/include/clang/AST/ExprCXX.h
+++ b/include/clang/AST/ExprCXX.h
@@ -3616,6 +3616,73 @@ public:
   child_range children() { return child_range(); }
 };
 
+/// \brief Represents a reference to a function parameter pack that has been
+/// substituted but not yet expanded.
+///
+/// When a pack expansion contains multiple parameter packs at different levels,
+/// this node is used to represent a function parameter pack at an outer level
+/// which we have already substituted to refer to expanded parameters, but where
+/// the containing pack expansion cannot yet be expanded.
+///
+/// \code
+/// template<typename...Ts> struct S {
+///   template<typename...Us> auto f(Ts ...ts) -> decltype(g(Us(ts)...));
+/// };
+/// template struct S<int, int>;
+/// \endcode
+class FunctionParmPackExpr : public Expr {
+  /// \brief The function parameter pack which was referenced.
+  ParmVarDecl *ParamPack;
+
+  /// \brief The location of the function parameter pack reference.
+  SourceLocation NameLoc;
+
+  /// \brief The number of expansions of this pack.
+  unsigned NumParameters;
+
+  FunctionParmPackExpr(QualType T, ParmVarDecl *ParamPack,
+                       SourceLocation NameLoc, unsigned NumParams,
+                       Decl * const *Params);
+
+  friend class ASTReader;
+  friend class ASTStmtReader;
+
+public:
+  static FunctionParmPackExpr *Create(ASTContext &Context, QualType T,
+                                      ParmVarDecl *ParamPack,
+                                      SourceLocation NameLoc,
+                                      llvm::ArrayRef<Decl*> Params);
+  static FunctionParmPackExpr *CreateEmpty(ASTContext &Context,
+                                           unsigned NumParams);
+
+  /// \brief Get the parameter pack which this expression refers to.
+  ParmVarDecl *getParameterPack() const { return ParamPack; }
+
+  /// \brief Get the location of the parameter pack.
+  SourceLocation getParameterPackLocation() const { return NameLoc; }
+
+  /// \brief Iterators over the parameters which the parameter pack expanded
+  /// into.
+  typedef ParmVarDecl * const *iterator;
+  iterator begin() const { return reinterpret_cast<iterator>(this+1); }
+  iterator end() const { return begin() + NumParameters; }
+
+  /// \brief Get the number of parameters in this parameter pack.
+  unsigned getNumExpansions() const { return NumParameters; }
+
+  /// \brief Get an expansion of the parameter pack by index.
+  ParmVarDecl *getExpansion(unsigned I) const { return begin()[I]; }
+
+  SourceRange getSourceRange() const LLVM_READONLY { return NameLoc; }
+
+  static bool classof(const Stmt *T) {
+    return T->getStmtClass() == FunctionParmPackExprClass;
+  }
+  static bool classof(const FunctionParmPackExpr *) { return true; }
+
+  child_range children() { return child_range(); }
+};
+
 /// \brief Represents a prvalue temporary that written into memory so that
 /// a reference can bind to it.
 ///
diff --git a/include/clang/AST/RecursiveASTVisitor.h b/include/clang/AST/RecursiveASTVisitor.h
index ae4ff4b1f8..22cd290858 100644
--- a/include/clang/AST/RecursiveASTVisitor.h
+++ b/include/clang/AST/RecursiveASTVisitor.h
@@ -2221,6 +2221,7 @@ DEF_TRAVERSE_STMT(PackExpansionExpr, { })
 DEF_TRAVERSE_STMT(SizeOfPackExpr, { })
 DEF_TRAVERSE_STMT(SubstNonTypeTemplateParmPackExpr, { })
 DEF_TRAVERSE_STMT(SubstNonTypeTemplateParmExpr, { })
+DEF_TRAVERSE_STMT(FunctionParmPackExpr, { })
 DEF_TRAVERSE_STMT(MaterializeTemporaryExpr, { })
 DEF_TRAVERSE_STMT(AtomicExpr, { })
 
diff --git a/include/clang/Basic/StmtNodes.td b/include/clang/Basic/StmtNodes.td
index 06da94708f..8f6a1c9f98 100644
--- a/include/clang/Basic/StmtNodes.td
+++ b/include/clang/Basic/StmtNodes.td
@@ -131,6 +131,7 @@ def PackExpansionExpr : DStmt<Expr>;
 def SizeOfPackExpr : DStmt<Expr>;
 def SubstNonTypeTemplateParmExpr : DStmt<Expr>;
 def SubstNonTypeTemplateParmPackExpr : DStmt<Expr>;
+def FunctionParmPackExpr : DStmt<Expr>;
 def MaterializeTemporaryExpr : DStmt<Expr>;
 def LambdaExpr : DStmt<Expr>;
 
diff --git a/include/clang/Serialization/ASTBitCodes.h b/include/clang/Serialization/ASTBitCodes.h
index e714da771b..5f127d252f 100644
--- a/include/clang/Serialization/ASTBitCodes.h
+++ b/include/clang/Serialization/ASTBitCodes.h
@@ -1193,6 +1193,7 @@ namespace clang {
       EXPR_SIZEOF_PACK,           // SizeOfPackExpr
       EXPR_SUBST_NON_TYPE_TEMPLATE_PARM, // SubstNonTypeTemplateParmExpr
       EXPR_SUBST_NON_TYPE_TEMPLATE_PARM_PACK,// SubstNonTypeTemplateParmPackExpr
+      EXPR_FUNCTION_PARM_PACK,    // FunctionParmPackExpr
       EXPR_MATERIALIZE_TEMPORARY, // MaterializeTemporaryExpr
       
       // CUDA