3 files changed, 30 insertions, 7 deletions
diff --git a/clang/include/clang/AST/DeclTemplate.h b/clang/include/clang/AST/DeclTemplate.h
index 8671d95c104..2af95c02c46 100644
--- a/clang/include/clang/AST/DeclTemplate.h
+++ b/clang/include/clang/AST/DeclTemplate.h
@@ -43,6 +43,8 @@ class VarTemplatePartialSpecializationDecl;
 typedef llvm::PointerUnion3<TemplateTypeParmDecl*, NonTypeTemplateParmDecl*,
                             TemplateTemplateParmDecl*> TemplateParameter;
 
+NamedDecl *getAsNamedDecl(TemplateParameter P);
+
 /// \brief Stores a list of template parameters for a TemplateDecl and its
 /// derived classes.
 class TemplateParameterList final
@@ -2937,6 +2939,14 @@ public:
   friend class ASTDeclWriter;
 };
 
+inline NamedDecl *getAsNamedDecl(TemplateParameter P) {
+  if (auto *PD = P.dyn_cast<TemplateTypeParmDecl*>())
+    return PD;
+  if (auto *PD = P.dyn_cast<NonTypeTemplateParmDecl*>())
+    return PD;
+  return P.get<TemplateTemplateParmDecl*>();
+}
+
 } /* end of namespace clang */
 
 #endif
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index ff98590057d..7d0b9d77419 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -7001,6 +7001,10 @@ def err_in_class_initializer_not_yet_parsed
 def err_in_class_initializer_not_yet_parsed_outer_class
     : Error<"cannot use defaulted default constructor of %0 within "
             "%1 outside of member functions because %2 has an initializer">;
+def err_in_class_initializer_cycle
+    : Error<"default member initializer for %0 uses itself">;
+def err_exception_spec_cycle
+    : Error<"exception specification of %0 uses itself">;
 
 def ext_in_class_initializer_non_constant : Extension<
   "in-class initializer for static data member is not a constant expression; "
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 668399bf846..9dbef558f04 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -18,6 +18,7 @@
 #include "clang/AST/Attr.h"
 #include "clang/AST/Availability.h"
 #include "clang/AST/DeclarationName.h"
+#include "clang/AST/DeclTemplate.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/ExprObjC.h"
 #include "clang/AST/ExternalASTSource.h"
@@ -6668,10 +6669,10 @@ public:
       TemplateInstantiation,
 
       /// We are instantiating a default argument for a template
-      /// parameter. The Entity is the template, and
-      /// TemplateArgs/NumTemplateArguments provides the template
-      /// arguments as specified.
-      /// FIXME: Use a TemplateArgumentList
+      /// parameter. The Entity is the template parameter whose argument is
+      /// being instantiated, the Template is the template, and the
+      /// TemplateArgs/NumTemplateArguments provide the template arguments as
+      /// specified.
       DefaultTemplateArgumentInstantiation,
 
       /// We are instantiating a default argument for a function.
@@ -6786,6 +6787,9 @@ public:
   SmallVector<ActiveTemplateInstantiation, 16>
     ActiveTemplateInstantiations;
 
+  /// Specializations whose definitions are currently being instantiated.
+  llvm::DenseSet<std::pair<Decl *, unsigned>> InstantiatingSpecializations;
+
   /// \brief Extra modules inspected when performing a lookup during a template
   /// instantiation. Computed lazily.
   SmallVector<Module*, 16> ActiveTemplateInstantiationLookupModules;
@@ -6892,12 +6896,12 @@ public:
     /// \brief Note that we are instantiating a default argument in a
     /// template-id.
     InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
-                          TemplateDecl *Template,
+                          TemplateParameter Param, TemplateDecl *Template,
                           ArrayRef<TemplateArgument> TemplateArgs,
                           SourceRange InstantiationRange = SourceRange());
 
-    /// \brief Note that we are instantiating a default argument in a
-    /// template-id.
+    /// \brief Note that we are substituting either explicitly-specified or
+    /// deduced template arguments during function template argument deduction.
     InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                           FunctionTemplateDecl *FunctionTemplate,
                           ArrayRef<TemplateArgument> TemplateArgs,
@@ -6964,9 +6968,14 @@ public:
     /// recursive template instantiations.
     bool isInvalid() const { return Invalid; }
 
+    /// \brief Determine whether we are already instantiating this
+    /// specialization in some surrounding active instantiation.
+    bool isAlreadyInstantiating() const { return AlreadyInstantiating; }
+
   private:
     Sema &SemaRef;
     bool Invalid;
+    bool AlreadyInstantiating;
     bool SavedInNonInstantiationSFINAEContext;
     bool CheckInstantiationDepth(SourceLocation PointOfInstantiation,
                                  SourceRange InstantiationRange);