3 files changed, 53 insertions, 2 deletions

diff --git a/clang/include/clang/Basic/DiagnosticParseKinds.td b/clang/include/clang/Basic/DiagnosticParseKinds.td
index f0add4c067d..8595c43aa86 100644
--- a/clang/include/clang/Basic/DiagnosticParseKinds.td
+++ b/clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -75,6 +75,10 @@ def warn_cxx98_compat_alignof : Warning<
   "alignof expressions are incompatible with C++98">,
   InGroup<CXX98Compat>, DefaultIgnore;
 
+def warn_microsoft_dependent_exists : Warning<
+  "dependent %select{__if_not_exists|__if_exists}0 declarations are ignored">, 
+  InGroup<DiagGroup<"microsoft-exists">>;
+
 def ext_c1x_generic_selection : Extension<
   "generic selections are a C1X-specific feature">, InGroup<C1X>;
 def err_duplicate_default_assoc : Error<
diff --git a/clang/include/clang/Parse/Parser.h b/clang/include/clang/Parse/Parser.h
index 3bf473cbe1c..d8a13e7bc45 100644
--- a/clang/include/clang/Parse/Parser.h
+++ b/clang/include/clang/Parse/Parser.h
@@ -488,6 +488,7 @@ private:
                           const char *Msg = "", 
                           tok::TokenKind SkipToTok = tok::unknown);
     bool consumeClose();
+    void skipToEnd();
   };
 
   DelimiterTracker QuantityTracker;
@@ -1487,7 +1488,40 @@ private:
   StmtResult ParseReturnStatement(ParsedAttributes &Attr);
   StmtResult ParseAsmStatement(bool &msAsm);
   StmtResult ParseMicrosoftAsmStatement(SourceLocation AsmLoc);
-  bool ParseMicrosoftIfExistsCondition(bool& Result);
+  
+  /// \brief Describes the behavior that should be taken for an __if_exists
+  /// block.
+  enum IfExistsBehavior {
+    /// \brief Parse the block; this code is always used.
+    IEB_Parse,
+    /// \brief Skip the block entirely; this code is never used.
+    IEB_Skip,
+    /// \brief Parse the block as a dependent block, which may be used in
+    /// some template instantiations but not others.
+    IEB_Dependent
+  };
+  
+  /// \brief Describes the condition of a Microsoft __if_exists or 
+  /// __if_not_exists block.
+  struct IfExistsCondition {
+    /// \brief The location of the initial keyword.
+    SourceLocation KeywordLoc;
+    /// \brief Whether this is an __if_exists block (rather than an 
+    /// __if_not_exists block).
+    bool IsIfExists;
+    
+    /// \brief Nested-name-specifier preceding the name.
+    CXXScopeSpec SS;
+    
+    /// \brief The name we're looking for.
+    UnqualifiedId Name;
+
+    /// \brief The behavior of this __if_exists or __if_not_exists block
+    /// should.
+    IfExistsBehavior Behavior;
+};
+  
+  bool ParseMicrosoftIfExistsCondition(IfExistsCondition& Result);
   void ParseMicrosoftIfExistsStatement(StmtVector &Stmts);
   void ParseMicrosoftIfExistsExternalDeclaration();
   void ParseMicrosoftIfExistsClassDeclaration(DeclSpec::TST TagType,
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 024d2734377..22a308dd2ac 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -2591,7 +2591,20 @@ public:
 
   bool CheckCaseExpression(Expr *E);
 
-  bool CheckMicrosoftIfExistsSymbol(CXXScopeSpec &SS, UnqualifiedId &Name);
+  /// \brief Describes the result of an "if-exists" condition check.
+  enum IfExistsResult {
+    /// \brief The symbol exists.
+    IER_Exists,
+    
+    /// \brief The symbol does not exist.
+    IER_DoesNotExist,
+    
+    /// \brief The name is a dependent name, so it 
+    IER_Dependent
+  };
+  
+  IfExistsResult 
+  CheckMicrosoftIfExistsSymbol(Scope *S, CXXScopeSpec &SS, UnqualifiedId &Name);
 
   //===------------------------- "Block" Extension ------------------------===//