[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.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175900 91177308-0d34-0410-b5e6-96231b3b80d8

19 files changed, 81 insertions, 32 deletions

diff --git a/include/clang/AST/Decl.h b/include/clang/AST/Decl.h
index 010563fdd9..42e6ae0657 100644
--- a/include/clang/AST/Decl.h
+++ b/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/include/clang/AST/RecursiveASTVisitor.h b/include/clang/AST/RecursiveASTVisitor.h
index faec5ebe09..4b5e19e733 100644
--- a/include/clang/AST/RecursiveASTVisitor.h
+++ b/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/include/clang/Basic/DeclNodes.td b/include/clang/Basic/DeclNodes.td
index 6f2bb35725..ac7ad6fc6a 100644
--- a/include/clang/Basic/DeclNodes.td
+++ b/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/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index e87cdd7673..13e52e0c6c 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/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/include/clang/Sema/Sema.h b/include/clang/Sema/Sema.h
index 7101286a7b..669cf9e814 100644
--- a/include/clang/Sema/Sema.h
+++ b/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/include/clang/Serialization/ASTBitCodes.h b/include/clang/Serialization/ASTBitCodes.h
index a672c7e149..93c5c073d5 100644
--- a/include/clang/Serialization/ASTBitCodes.h
+++ b/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/lib/AST/Decl.cpp b/lib/AST/Decl.cpp
index 0dbb0d30aa..d2a9f84cd4 100644
--- a/lib/AST/Decl.cpp
+++ b/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/lib/AST/DeclBase.cpp b/lib/AST/DeclBase.cpp
index f675436fc5..cdf150595c 100644
--- a/lib/AST/DeclBase.cpp
+++ b/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/lib/AST/DeclPrinter.cpp b/lib/AST/DeclPrinter.cpp
index dce4f9af25..2be0b6c804 100644
--- a/lib/AST/DeclPrinter.cpp
+++ b/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/lib/CodeGen/CGDecl.cpp b/lib/CodeGen/CGDecl.cpp
index a4d673b8c3..9c523149bd 100644
--- a/lib/CodeGen/CGDecl.cpp
+++ b/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/lib/CodeGen/CodeGenModule.cpp b/lib/CodeGen/CodeGenModule.cpp
index 60ec323203..6442f04070 100644
--- a/lib/CodeGen/CodeGenModule.cpp
+++ b/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/lib/Parse/Parser.cpp b/lib/Parse/Parser.cpp
index d9772755bd..24849edd63 100644
--- a/lib/Parse/Parser.cpp
+++ b/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/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index 8198856547..ce526a9ed3 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/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/lib/Serialization/ASTCommon.cpp b/lib/Serialization/ASTCommon.cpp
index 9f1514bdff..3319cc3641 100644
--- a/lib/Serialization/ASTCommon.cpp
+++ b/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/lib/Serialization/ASTReaderDecl.cpp b/lib/Serialization/ASTReaderDecl.cpp
index f4d03cf775..504c2e6588 100644
--- a/lib/Serialization/ASTReaderDecl.cpp
+++ b/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/lib/Serialization/ASTWriterDecl.cpp b/lib/Serialization/ASTWriterDecl.cpp
index 3795e21bdf..6c63a149c2 100644
--- a/lib/Serialization/ASTWriterDecl.cpp
+++ b/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/test/Parser/cxx0x-attributes.cpp b/test/Parser/cxx0x-attributes.cpp
index 4e7ac16cc5..5e4e388a26 100644
--- a/test/Parser/cxx0x-attributes.cpp
+++ b/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/test/SemaCXX/cxx11-ast-print.cpp b/test/SemaCXX/cxx11-ast-print.cpp
index 66ff0f064a..8e9480476c 100644
--- a/test/SemaCXX/cxx11-ast-print.cpp
+++ b/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/tools/libclang/RecursiveASTVisitor.h b/tools/libclang/RecursiveASTVisitor.h
index 35d59d02cd..9788c956da 100644
--- a/tools/libclang/RecursiveASTVisitor.h
+++ b/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()));
   })