5 files changed, 45 insertions, 2 deletions
diff --git a/clang/include/clang/AST/DeclBase.h b/clang/include/clang/AST/DeclBase.h
index 811e966172f..e2ca1a3298b 100644
--- a/clang/include/clang/AST/DeclBase.h
+++ b/clang/include/clang/AST/DeclBase.h
@@ -156,6 +156,10 @@ private:
   /// the implementation rather than explicitly written by the user.
   bool Implicit : 1;
 
+  /// \brief Whether this declaration was "used", meaning that a definition is
+  /// required.
+  bool Used : 1;
+  
   /// IdentifierNamespace - This specifies what IDNS_* namespace this lives in.
   unsigned IdentifierNamespace : 8;
   
@@ -174,7 +178,7 @@ protected:
   Decl(Kind DK, DeclContext *DC, SourceLocation L) 
     : NextDeclInContext(0), DeclCtx(DC), 
       Loc(L), DeclKind(DK), InvalidDecl(0),
-      HasAttrs(false), Implicit(false), 
+      HasAttrs(false), Implicit(false), Used(false),
       IdentifierNamespace(getIdentifierNamespaceForKind(DK)), Access(AS_none) {
     if (Decl::CollectingStats()) addDeclKind(DK);
   }
@@ -241,6 +245,11 @@ public:
   bool isImplicit() const { return Implicit; }
   void setImplicit(bool I = true) { Implicit = I; }
   
+  /// \brief Whether this declaration was used, meaning that a definition
+  /// is required.
+  bool isUsed() const { return Used; }
+  void setUsed(bool U = true) { Used = U; }
+  
   unsigned getIdentifierNamespace() const {
     return IdentifierNamespace;
   }
diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index ef16b4e69e3..2896f7988c0 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -116,7 +116,9 @@ def Format2 : DiagGroup<"format=2",
                         [FormatNonLiteral, FormatSecurity, FormatY2K]>;
 
 
-def Extra : DiagGroup<"extra">;
+def Extra : DiagGroup<"extra", [
+    UnusedParameter
+  ]>;
 
 def Most : DiagGroup<"most", [
     Comment,
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 5b324d87c0f..855b7b9d29d 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -72,6 +72,8 @@ def ext_anon_param_requires_type_specifier : Extension<
 def err_bad_variable_name : Error<
   "'%0' cannot be the name of a variable or data member">;
 def err_parameter_name_omitted : Error<"parameter name omitted">;
+def warn_unused_parameter : Warning<"unused parameter %0">,
+  InGroup<UnusedParameter>, DefaultIgnore;
 def warn_decl_in_param_list : Warning<
   "declaration of %0 will not be visible outside of this function">;
   
diff --git a/clang/include/clang/Parse/Action.h b/clang/include/clang/Parse/Action.h
index ba480c5b7c4..47583993bc2 100644
--- a/clang/include/clang/Parse/Action.h
+++ b/clang/include/clang/Parse/Action.h
@@ -637,6 +637,18 @@ public:
   // Expression Parsing Callbacks.
   //===--------------------------------------------------------------------===//
 
+  /// \brief Notifies the action when the parser is processing an unevaluated
+  /// operand.
+  ///
+  /// \param UnevaluatedOperand true to indicate that the parser is processing
+  /// an unevaluated operand, or false otherwise.
+  ///
+  /// \returns whether the the action module was previously in an unevaluated
+  /// operand.
+  virtual bool setUnevaluatedOperand(bool UnevaluatedOperand) { 
+    return false;
+  }
+  
   // Primary Expressions.
 
   /// \brief Retrieve the source range that corresponds to the given
diff --git a/clang/include/clang/Parse/Parser.h b/clang/include/clang/Parse/Parser.h
index d613ae13293..75458d821e8 100644
--- a/clang/include/clang/Parse/Parser.h
+++ b/clang/include/clang/Parse/Parser.h
@@ -105,6 +105,24 @@ class Parser {
     }
   };
 
+  /// \brief RAII object that enters an unevaluated operand.
+  class EnterUnevaluatedOperand {    
+    /// \brief The action object.
+    Action &Actions;
+    
+    /// \brief Whether we were previously within an unevaluated operand.
+    bool PreviouslyInUnevaluatedOperand;
+    
+  public:
+    explicit EnterUnevaluatedOperand(Action &Actions) : Actions(Actions) { 
+      PreviouslyInUnevaluatedOperand = Actions.setUnevaluatedOperand(true);
+    }
+    
+    ~EnterUnevaluatedOperand() {
+      Actions.setUnevaluatedOperand(PreviouslyInUnevaluatedOperand);
+    }
+  };
+  
 public:
   Parser(Preprocessor &PP, Action &Actions);
   ~Parser();