[Sema] Semantic analysis for empty-declaration and attribute-declaration.

Introduce a new AST Decl node "EmptyDecl" to model empty-declaration. Have attributes from attribute-declaration appertain
to the EmptyDecl node by creating the AST representations of these attributes and attach them to the EmptyDecl node so these
attributes can be sema checked just as attributes attached to "normal" declarations.

llvm-svn: 175900

19 files changed, 81 insertions, 32 deletions

diff --git a/clang/include/clang/AST/Decl.h b/clang/include/clang/AST/Decl.h
index 010563fdd95..42e6ae0657d 100644
--- a/clang/include/clang/AST/Decl.h
+++ b/clang/include/clang/AST/Decl.h
@@ -3297,7 +3297,21 @@ public:
   static bool classof(const Decl *D) { return classofKind(D->getKind()); }
   static bool classofKind(Kind K) { return K == Import; }
 };
-  
+
+/// \brief Represents an empty-declaration.
+class EmptyDecl : public Decl {
+  virtual void anchor();
+  EmptyDecl(DeclContext *DC, SourceLocation L)
+    : Decl(Empty, DC, L) { }
+
+public:
+  static EmptyDecl *Create(ASTContext &C, DeclContext *DC,
+                           SourceLocation L);
+  static EmptyDecl *CreateDeserialized(ASTContext &C, unsigned ID);
+
+  static bool classof(const Decl *D) { return classofKind(D->getKind()); }
+  static bool classofKind(Kind K) { return K == Empty; }
+};
 
 /// Insertion operator for diagnostics.  This allows sending NamedDecl's
 /// into a diagnostic with <<.
diff --git a/clang/include/clang/AST/RecursiveASTVisitor.h b/clang/include/clang/AST/RecursiveASTVisitor.h
index faec5ebe09c..4b5e19e7332 100644
--- a/clang/include/clang/AST/RecursiveASTVisitor.h
+++ b/clang/include/clang/AST/RecursiveASTVisitor.h
@@ -1257,6 +1257,8 @@ DEF_TRAVERSE_DECL(BlockDecl, {
     return true;
   })
 
+DEF_TRAVERSE_DECL(EmptyDecl, { })
+
 DEF_TRAVERSE_DECL(FileScopeAsmDecl, {
     TRY_TO(TraverseStmt(D->getAsmString()));
   })
diff --git a/clang/include/clang/Basic/DeclNodes.td b/clang/include/clang/Basic/DeclNodes.td
index 6f2bb357251..ac7ad6fc6a7 100644
--- a/clang/include/clang/Basic/DeclNodes.td
+++ b/clang/include/clang/Basic/DeclNodes.td
@@ -74,4 +74,5 @@ def StaticAssert : Decl;
 def Block : Decl, DeclContext;
 def ClassScopeFunctionSpecialization : Decl;
 def Import : Decl;
+def Empty : Decl;
 
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index e87cdd7673e..13e52e0c6c1 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1916,8 +1916,6 @@ def warn_attribute_not_on_decl : Warning<
   "%0 attribute ignored when parsing type">, InGroup<IgnoredAttributes>;
 def err_base_specifier_attribute : Error<
   "%0 attribute cannot be applied to a base specifier">;
-def err_attribute_declaration : Error<
-  "%0 attribute cannot be used in an attribute declaration">;
 
 // Availability attribute
 def warn_availability_unknown_platform : Warning<
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 7101286a7b0..669cf9e814a 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -1447,8 +1447,10 @@ public:
                               SourceLocation AsmLoc,
                               SourceLocation RParenLoc);
 
-  /// \brief Handle a C++11 attribute-declaration.
-  void ActOnAttributeDeclaration(AttributeList *AttrList);
+  /// \brief Handle a C++11 empty-declaration and attribute-declaration.
+  Decl *ActOnEmptyDeclaration(Scope *S,
+                              AttributeList *AttrList,
+                              SourceLocation SemiLoc);
 
   /// \brief The parser has processed a module import declaration.
   ///
diff --git a/clang/include/clang/Serialization/ASTBitCodes.h b/clang/include/clang/Serialization/ASTBitCodes.h
index a672c7e149e..93c5c073d53 100644
--- a/clang/include/clang/Serialization/ASTBitCodes.h
+++ b/clang/include/clang/Serialization/ASTBitCodes.h
@@ -1031,7 +1031,9 @@ namespace clang {
       /// function specialization. (Microsoft extension).
       DECL_CLASS_SCOPE_FUNCTION_SPECIALIZATION,
       /// \brief An ImportDecl recording a module import.
-      DECL_IMPORT
+      DECL_IMPORT,
+      /// \brief An EmptyDecl record.
+      DECL_EMPTY
     };
 
     /// \brief Record codes for each kind of statement or expression.
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 0dbb0d30aa2..d2a9f84cd4f 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -3343,6 +3343,17 @@ FileScopeAsmDecl *FileScopeAsmDecl::CreateDeserialized(ASTContext &C,
   return new (Mem) FileScopeAsmDecl(0, 0, SourceLocation(), SourceLocation());
 }
 
+void EmptyDecl::anchor() {}
+
+EmptyDecl *EmptyDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation L) {
+  return new (C) EmptyDecl(DC, L);
+}
+
+EmptyDecl *EmptyDecl::CreateDeserialized(ASTContext &C, unsigned ID) {
+  void *Mem = AllocateDeserializedDecl(C, ID, sizeof(EmptyDecl));
+  return new (Mem) EmptyDecl(0, SourceLocation());
+}
+
 //===----------------------------------------------------------------------===//
 // ImportDecl Implementation
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
index f675436fc5f..cdf150595c3 100644
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -558,6 +558,7 @@ unsigned Decl::getIdentifierNamespaceForKind(Kind DeclKind) {
     case ObjCCategory:
     case ObjCCategoryImpl:
     case Import:
+    case Empty:
       // Never looked up by name.
       return 0;
   }
diff --git a/clang/lib/AST/DeclPrinter.cpp b/clang/lib/AST/DeclPrinter.cpp
index dce4f9af258..2be0b6c8046 100644
--- a/clang/lib/AST/DeclPrinter.cpp
+++ b/clang/lib/AST/DeclPrinter.cpp
@@ -51,6 +51,7 @@ namespace {
     void VisitEnumDecl(EnumDecl *D);
     void VisitRecordDecl(RecordDecl *D);
     void VisitEnumConstantDecl(EnumConstantDecl *D);
+    void VisitEmptyDecl(EmptyDecl *D);
     void VisitFunctionDecl(FunctionDecl *D);
     void VisitFriendDecl(FriendDecl *D);
     void VisitFieldDecl(FieldDecl *D);
@@ -723,6 +724,11 @@ void DeclPrinter::VisitNamespaceAliasDecl(NamespaceAliasDecl *D) {
   Out << *D->getAliasedNamespace();
 }
 
+void DeclPrinter::VisitEmptyDecl(EmptyDecl *D) {
+  prettyPrintAttributes(D);
+  Out << ";\n";
+}
+
 void DeclPrinter::VisitCXXRecordDecl(CXXRecordDecl *D) {
   if (!Policy.SuppressSpecifiers && D->isModulePrivate())
     Out << "__module_private__ ";
diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index a4d673b8c32..9c523149bdf 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -83,6 +83,7 @@ void CodeGenFunction::EmitDecl(const Decl &D) {
   case Decl::StaticAssert: // static_assert(X, ""); [C++0x]
   case Decl::Label:        // __label__ x;
   case Decl::Import:
+  case Decl::Empty:
     // None of these decls require codegen support.
     return;
 
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 60ec3232031..6442f04070d 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -2742,6 +2742,7 @@ void CodeGenModule::EmitTopLevelDecl(Decl *D) {
   case Decl::TypeAliasTemplate:
   case Decl::NamespaceAlias:
   case Decl::Block:
+  case Decl::Empty:
     break;
   case Decl::CXXConstructor:
     // Skip function templates
diff --git a/clang/lib/Parse/Parser.cpp b/clang/lib/Parse/Parser.cpp
index d9772755bd2..24849edd63b 100644
--- a/clang/lib/Parse/Parser.cpp
+++ b/clang/lib/Parse/Parser.cpp
@@ -626,15 +626,11 @@ Parser::ParseExternalDeclaration(ParsedAttributesWithRange &attrs,
     return DeclGroupPtrTy();
   case tok::semi:
     // Either a C++11 empty-declaration or attribute-declaration.
-    if (attrs.Range.isValid()) {
-      // FIXME: Add an AST representation for this.
-      Actions.ActOnAttributeDeclaration(attrs.getList());
-      return DeclGroupPtrTy();
-    }
-
+    SingleDecl = Actions.ActOnEmptyDeclaration(getCurScope(),
+                                               attrs.getList(),
+                                               Tok.getLocation());
     ConsumeExtraSemi(OutsideFunction);
-    // TODO: Invoke action for top-level semicolon.
-    return DeclGroupPtrTy();
+    break;
   case tok::r_brace:
     Diag(Tok, diag::err_extraneous_closing_brace);
     ConsumeBrace();
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 8198856547c..ce526a9ed39 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -10085,23 +10085,17 @@ Decl *Sema::ActOnFinishLinkageSpecification(Scope *S,
   return LinkageSpec;
 }
 
-/// \brief Perform semantic checks on a C++11 attribute-declaration.
-void Sema::ActOnAttributeDeclaration(AttributeList *AttrList) {
-  // FIXME: Build an AST node for an attribute declaration and return it.
-  
-  // Since we do not support any attributes which can be used in an attribute
-  // declaration, just diagnose standard and unknown attributes appropriately.
-  for (/**/; AttrList; AttrList = AttrList->getNext()) {
-    if (AttrList->getKind() == AttributeList::IgnoredAttribute ||
-        AttrList->isInvalid())
-      continue;
-
-    Diag(AttrList->getLoc(),
-         AttrList->getKind() == AttributeList::UnknownAttribute
-           ? diag::warn_unknown_attribute_ignored
-           : diag::err_attribute_declaration)
-      << AttrList->getName();
-  }
+Decl *Sema::ActOnEmptyDeclaration(Scope *S,
+                                  AttributeList *AttrList,
+                                  SourceLocation SemiLoc) {
+  Decl *ED = EmptyDecl::Create(Context, CurContext, SemiLoc);
+  // Attribute declarations appertain to empty declaration so we handle
+  // them here.
+  if (AttrList)
+    ProcessDeclAttributeList(S, ED, AttrList);
+
+  CurContext->addDecl(ED);
+  return ED;
 }
 
 /// \brief Perform semantic analysis for the variable declaration that
diff --git a/clang/lib/Serialization/ASTCommon.cpp b/clang/lib/Serialization/ASTCommon.cpp
index 9f1514bdff2..3319cc36412 100644
--- a/clang/lib/Serialization/ASTCommon.cpp
+++ b/clang/lib/Serialization/ASTCommon.cpp
@@ -168,6 +168,7 @@ bool serialization::isRedeclarableDeclKind(unsigned Kind) {
   case Decl::TypeAliasTemplate:
   case Decl::ObjCProtocol:
   case Decl::ObjCInterface:
+  case Decl::Empty:
     return true;
 
   // Never redeclarable.
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index f4d03cf7755..504c2e6588b 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -265,6 +265,7 @@ namespace clang {
     void VisitFriendTemplateDecl(FriendTemplateDecl *D);
     void VisitStaticAssertDecl(StaticAssertDecl *D);
     void VisitBlockDecl(BlockDecl *BD);
+    void VisitEmptyDecl(EmptyDecl *D);
 
     std::pair<uint64_t, uint64_t> VisitDeclContext(DeclContext *DC);
     
@@ -1526,6 +1527,10 @@ void ASTDeclReader::VisitStaticAssertDecl(StaticAssertDecl *D) {
   D->RParenLoc = ReadSourceLocation(Record, Idx);
 }
 
+void ASTDeclReader::VisitEmptyDecl(EmptyDecl *D) {
+  VisitDecl(D);
+}
+
 std::pair<uint64_t, uint64_t>
 ASTDeclReader::VisitDeclContext(DeclContext *DC) {
   uint64_t LexicalOffset = Record[Idx++];
@@ -2129,6 +2134,9 @@ Decl *ASTReader::ReadDeclRecord(DeclID ID) {
     // locations.
     D = ImportDecl::CreateDeserialized(Context, ID, Record.back());
     break;
+  case DECL_EMPTY:
+    D = EmptyDecl::CreateDeserialized(Context, ID);
+    break;
   }
 
   assert(D && "Unknown declaration reading AST file");
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index 3795e21bdf6..6c63a149c2b 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -102,6 +102,7 @@ namespace clang {
     void VisitFriendTemplateDecl(FriendTemplateDecl *D);
     void VisitStaticAssertDecl(StaticAssertDecl *D);
     void VisitBlockDecl(BlockDecl *D);
+    void VisitEmptyDecl(EmptyDecl *D);
 
     void VisitDeclContext(DeclContext *DC, uint64_t LexicalOffset,
                           uint64_t VisibleOffset);
@@ -780,6 +781,11 @@ void ASTDeclWriter::VisitFileScopeAsmDecl(FileScopeAsmDecl *D) {
   Code = serialization::DECL_FILE_SCOPE_ASM;
 }
 
+void ASTDeclWriter::VisitEmptyDecl(EmptyDecl *D) {
+  VisitDecl(D);
+  Code = serialization::DECL_EMPTY;
+}
+
 void ASTDeclWriter::VisitBlockDecl(BlockDecl *D) {
   VisitDecl(D);
   Writer.AddStmt(D->getBody());
diff --git a/clang/test/Parser/cxx0x-attributes.cpp b/clang/test/Parser/cxx0x-attributes.cpp
index 4e7ac16cc5d..5e4e388a264 100644
--- a/clang/test/Parser/cxx0x-attributes.cpp
+++ b/clang/test/Parser/cxx0x-attributes.cpp
@@ -279,4 +279,5 @@ int v4[2][[gnu::unused]]; // expected-warning {{attribute 'unused' ignored}}
 int v5()[[gnu::unused]]; // expected-warning {{attribute 'unused' ignored}}
 
 [[attribute_declaration]]; // expected-warning {{unknown attribute 'attribute_declaration' ignored}}
-[[noreturn]]; // expected-error {{'noreturn' attribute cannot be used in an attribute declaration}}
+[[noreturn]]; // expected-error {{'noreturn' attribute only applies to functions and methods}}
+[[carries_dependency]]; // expected-error {{'carries_dependency' attribute only applies to functions, methods, and parameters}}
diff --git a/clang/test/SemaCXX/cxx11-ast-print.cpp b/clang/test/SemaCXX/cxx11-ast-print.cpp
index 66ff0f064a3..8e9480476c1 100644
--- a/clang/test/SemaCXX/cxx11-ast-print.cpp
+++ b/clang/test/SemaCXX/cxx11-ast-print.cpp
@@ -38,3 +38,5 @@ const char *p8 = 4.9_quux;
 const char *p9 = 0x42e3F_fritz;
 // CHECK: const char *p10 = 3.300e+15_fritz;
 const char *p10 = 3.300e+15_fritz;
+// CHECK: ;
+;
diff --git a/clang/tools/libclang/RecursiveASTVisitor.h b/clang/tools/libclang/RecursiveASTVisitor.h
index 35d59d02cde..9788c956da0 100644
--- a/clang/tools/libclang/RecursiveASTVisitor.h
+++ b/clang/tools/libclang/RecursiveASTVisitor.h
@@ -1199,6 +1199,8 @@ DEF_TRAVERSE_DECL(BlockDecl, {
     return true;
   })
 
+DEF_TRAVERSE_DECL(EmptyDecl, { })
+
 DEF_TRAVERSE_DECL(FileScopeAsmDecl, {
     TRY_TO(TraverseStmt(D->getAsmString()));
   })