6 files changed, 49 insertions, 3 deletions
diff --git a/include/clang/AST/DeclTemplate.h b/include/clang/AST/DeclTemplate.h
index ccbe1288f8..334a03a439 100644
--- a/include/clang/AST/DeclTemplate.h
+++ b/include/clang/AST/DeclTemplate.h
@@ -66,9 +66,19 @@ public:
 
   unsigned size() const { return NumParams; }
 
+  /// \btief Returns the minimum number of arguments needed to form a
+  /// template specialization. This may be fewer than the number of
+  /// template parameters, if some of the parameters have default
+  /// arguments.
+  unsigned getMinRequiredArguments() const;
+
   SourceLocation getTemplateLoc() const { return TemplateLoc; }
   SourceLocation getLAngleLoc() const { return LAngleLoc; }
   SourceLocation getRAngleLoc() const { return RAngleLoc; }
+
+  SourceRange getSourceRange() const {
+    return SourceRange(TemplateLoc, RAngleLoc);
+  }
 };
 
 //===----------------------------------------------------------------------===//
diff --git a/include/clang/Basic/DiagnosticSemaKinds.def b/include/clang/Basic/DiagnosticSemaKinds.def
index 4fed9443d0..25fe8254bb 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.def
+++ b/include/clang/Basic/DiagnosticSemaKinds.def
@@ -505,6 +505,8 @@ DIAG(err_template_param_default_arg_missing, ERROR,
 // C++ Template Argument Lists
 DIAG(err_template_arg_list_different_arity, ERROR,
      "%select{too few|too many}0 template arguments for %select{class template|function template|template template parameter|template}1 %2")
+DIAG(note_template_decl_here, NOTE,
+     "template is declared here")
 DIAG(err_template_arg_must_be_type, ERROR,
      "template argument for template type parameter must be a type")
 DIAG(err_template_arg_must_be_expr, ERROR,
diff --git a/lib/AST/DeclTemplate.cpp b/lib/AST/DeclTemplate.cpp
index b297dd25cb..dccb8df075 100644
--- a/lib/AST/DeclTemplate.cpp
+++ b/lib/AST/DeclTemplate.cpp
@@ -44,6 +44,26 @@ TemplateParameterList::Create(ASTContext &C, SourceLocation TemplateLoc,
                                          NumParams, RAngleLoc);
 }
 
+unsigned TemplateParameterList::getMinRequiredArguments() const {
+  unsigned NumRequiredArgs = size();
+  iterator Param = const_cast<TemplateParameterList *>(this)->end(), 
+      ParamBegin = const_cast<TemplateParameterList *>(this)->begin();
+  while (Param != ParamBegin) {
+    --Param;
+    if (!(isa<TemplateTypeParmDecl>(*Param) && 
+          cast<TemplateTypeParmDecl>(*Param)->hasDefaultArgument()) &&
+        !(isa<NonTypeTemplateParmDecl>(*Param) &&
+          cast<NonTypeTemplateParmDecl>(*Param)->hasDefaultArgument()) &&
+        !(isa<TemplateTemplateParmDecl>(*Param) &&
+          cast<TemplateTemplateParmDecl>(*Param)->hasDefaultArgument()))
+      break;
+        
+    --NumRequiredArgs;
+  }
+
+  return NumRequiredArgs;
+}
+
 //===----------------------------------------------------------------------===//
 // TemplateDecl Implementation
 //===----------------------------------------------------------------------===//
diff --git a/lib/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index 86f1e2017f..b4436a2c3c 100644
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -685,7 +685,7 @@ bool Sema::CheckTemplateArgumentList(TemplateDecl *Template,
   bool Invalid = false;
 
   if (NumArgs > NumParams ||
-      NumArgs < NumParams /*FIXME: default arguments! */) {
+      NumArgs < Params->getMinRequiredArguments()) {
     // FIXME: point at either the first arg beyond what we can handle,
     // or the '>', depending on whether we have too many or too few
     // arguments.
@@ -698,7 +698,8 @@ bool Sema::CheckTemplateArgumentList(TemplateDecl *Template,
           isa<FunctionTemplateDecl>(Template)? 1 :
           isa<TemplateTemplateParmDecl>(Template)? 2 : 3)
       << Template << Range;
-
+    Diag(Template->getLocation(), diag::note_template_decl_here)
+      << Params->getSourceRange();
     Invalid = true;
   }
   
diff --git a/test/SemaTemplate/default-arguments.cpp b/test/SemaTemplate/default-arguments.cpp
new file mode 100644
index 0000000000..94976e9735
--- /dev/null
+++ b/test/SemaTemplate/default-arguments.cpp
@@ -0,0 +1,13 @@
+// RUN: clang -fsyntax-only -verify %s
+
+template<typename T, int N = 2> struct X; // expected-note{{template is declared here}}
+
+X<int, 1> *x1;
+X<int> *x2;
+
+X<> *x3; // expected-error{{too few template arguments for class template 'X'}} \
+        // FIXME: expected-error{{expected unqualified-id}}
+
+template<typename U = float, int M> struct X;
+
+X<> *x4;
diff --git a/test/SemaTemplate/temp_arg.cpp b/test/SemaTemplate/temp_arg.cpp
index 0f69b5f4b1..b8bb279caf 100644
--- a/test/SemaTemplate/temp_arg.cpp
+++ b/test/SemaTemplate/temp_arg.cpp
@@ -2,7 +2,7 @@
 template<typename T, 
          int I, 
          template<typename> class TT>
-  class A;
+  class A; // expected-note 2 {{template is declared here}}
 
 template<typename> class X;