Teach DeclContext how to find the primary declaration for any TagDecl

even when we are still defining the TagDecl. This is required so that
qualified name lookup of a class name within its definition works (see
the new bits in test/SemaCXX/qualified-id-lookup.cpp).

As part of this, move the nested redefinition checking code into
ActOnTag. This gives us diagnostics earlier (when we try to perform
the nested redefinition, rather than when we try to complete the 2nd
definition) and removes some code duplication.

llvm-svn: 62386

clang/include/clang/AST/ASTContext.h

@@ -543,14 +543,6 @@ private:
   void InitBuiltinTypes();
   void InitBuiltinType(QualType &R, BuiltinType::Kind K);
   
-  /// setTagDefinition - Used by RecordDecl::completeDefinition and
-  /// EnumDecl::completeDefinition to inform 
-  /// about which RecordDecl/EnumDecl serves as the definition of a particular
-  /// struct/union/class/enum.
-  void setTagDefinition(TagDecl* R);
-  friend class EnumDecl;
-  friend class RecordDecl;
-
   // Return the ObjC type encoding for a given type.
   void getObjCEncodingForTypeImpl(QualType t, std::string &S, 
                                   bool ExpandPointedToStructures,

clang/include/clang/AST/Decl.h

@@ -887,6 +887,9 @@ class TypeDecl : public ScopedDecl {
   /// ASTContext::getTagDeclType, and ASTContext::getTemplateTypeParmType.
   Type *TypeForDecl;
   friend class ASTContext;
+  friend class DeclContext;
+  friend class TagDecl;
+
 protected:
   TypeDecl(Kind DK, DeclContext *DC, SourceLocation L,
            IdentifierInfo *Id, ScopedDecl *PrevDecl)
@@ -965,6 +968,16 @@ public:
     return IsDefinition;
   }
   
+  /// @brief Starts the definition of this tag declaration.
+  /// 
+  /// This method should be invoked at the beginning of the definition
+  /// of this tag declaration. It will set the tag type into a state
+  /// where it is in the process of being defined.
+  void startDefinition();
+
+  /// @brief Completes the definition of this tag declaration.
+  void completeDefinition();
+
   /// getDefinition - Returns the TagDecl that actually defines this 
   ///  struct/union/class/enum.  When determining whether or not a
   ///  struct/union/class/enum is completely defined, one should use this method
@@ -998,6 +1011,14 @@ public:
     return D->getKind() >= TagFirst && D->getKind() <= TagLast;
   }
   static bool classof(const TagDecl *D) { return true; }
+
+  static DeclContext *castToDeclContext(const TagDecl *D) {
+    return static_cast<DeclContext *>(const_cast<TagDecl*>(D));
+  }
+  static TagDecl *castFromDeclContext(const DeclContext *DC) {
+    return static_cast<TagDecl *>(const_cast<DeclContext*>(DC));
+  }
+
 protected:
   void setDefinition(bool V) { IsDefinition = V; }
 };

clang/include/clang/AST/Type.h

@@ -1194,18 +1194,29 @@ protected:
 };
 
 class TagType : public Type {
-  TagDecl *decl;
+  /// Stores the TagDecl associated with this type. The decl will
+  /// point to the TagDecl that actually defines the entity (or is a
+  /// definition in progress), if there is such a definition. The
+  /// single-bit value will be non-zero when this tag is in the
+  /// process of being defined.
+  llvm::PointerIntPair<TagDecl *, 1> decl;
   friend class ASTContext;
+  friend class TagDecl;
 
 protected:
   // FIXME: We'll need the user to pass in information about whether
   // this type is dependent or not, because we don't have enough
   // information to compute it here.
   TagType(TagDecl *D, QualType can) 
-    : Type(Tagged, can, /*Dependent=*/false), decl(D) {}
+    : Type(Tagged, can, /*Dependent=*/false), decl(D, 0) {}
 
 public:   
-  TagDecl *getDecl() const { return decl; }
+  TagDecl *getDecl() const { return decl.getPointer(); }
+  
+  /// @brief Determines whether this type is in the process of being
+  /// defined. 
+  bool isBeingDefined() const { return decl.getInt(); }
+  void setBeingDefined(bool Def) { decl.setInt(Def? 1 : 0); }
 
   virtual void getAsStringInternal(std::string &InnerString) const;
   

clang/include/clang/Basic/SourceLocation.h

@@ -253,17 +253,20 @@ public:
   /// Prints information about this FullSourceLoc to stderr. Useful for
   ///  debugging.
   void dump() const;
+
+  friend inline bool 
+  operator==(const FullSourceLoc &LHS, const FullSourceLoc &RHS) {
+    return LHS.getRawEncoding() == RHS.getRawEncoding() &&
+          LHS.SrcMgr == RHS.SrcMgr;
+  }
+
+  friend inline bool 
+  operator!=(const FullSourceLoc &LHS, const FullSourceLoc &RHS) {
+    return !(LHS == RHS);
+  }
+
 };
  
-inline bool operator==(const FullSourceLoc &LHS, const FullSourceLoc &RHS) {
-  return LHS.getRawEncoding() == RHS.getRawEncoding() &&
-         &LHS.getManager() == &RHS.getManager();
-}
-
-inline bool operator!=(const FullSourceLoc &LHS, const FullSourceLoc &RHS) {
-  return !(LHS == RHS);
-}
-  
 }  // end namespace clang
 
 #endif

clang/include/clang/Parse/Action.h

@@ -310,7 +310,7 @@ public:
     TK_Declaration, // Fwd decl of a tag:   'struct foo;'
     TK_Definition   // Definition of a tag: 'struct foo { int X; } Y;'
   };
-  virtual DeclTy *ActOnTag(Scope *S, unsigned TagType, TagKind TK,
+  virtual DeclTy *ActOnTag(Scope *S, unsigned TagSpec, TagKind TK,
                            SourceLocation KWLoc, const CXXScopeSpec &SS,
                            IdentifierInfo *Name, SourceLocation NameLoc,
                            AttributeList *Attr,

clang/lib/AST/ASTContext.cpp

@@ -1076,11 +1076,6 @@ QualType ASTContext::getTypeDeclType(TypeDecl *Decl, TypeDecl* PrevDecl) {
   return QualType(Decl->TypeForDecl, 0);
 }
 
-void ASTContext::setTagDefinition(TagDecl* D) {
-  assert (D->isDefinition());
-  cast<TagType>(D->TypeForDecl)->decl = D;  
-}
-
 /// getTypedefType - Return the unique reference to the type for the
 /// specified typename decl.
 QualType ASTContext::getTypedefType(TypedefDecl *Decl) {

clang/lib/AST/Decl.cpp

@@ -144,13 +144,8 @@ void EnumDecl::Destroy(ASTContext& C) {
 
 void EnumDecl::completeDefinition(ASTContext &C, QualType NewType) {
   assert(!isDefinition() && "Cannot redefine enums!");
-  setDefinition(true);
-
   IntegerType = NewType;
-
+  TagDecl::completeDefinition();
-  // Let ASTContext know that this is the defining EnumDecl for this
-  // type.
-  C.setTagDefinition(this);
 }
 
 FileScopeAsmDecl *FileScopeAsmDecl::Create(ASTContext &C,
@@ -311,6 +306,20 @@ OverloadedOperatorKind FunctionDecl::getOverloadedOperator() const {
 // TagDecl Implementation
 //===----------------------------------------------------------------------===//
 
+void TagDecl::startDefinition() {
+  cast<TagType>(TypeForDecl)->decl.setPointer(this);
+  cast<TagType>(TypeForDecl)->decl.setInt(1);
+}
+
+void TagDecl::completeDefinition() {
+  assert((!TypeForDecl || 
+          cast<TagType>(TypeForDecl)->decl.getPointer() == this) &&
+         "Attempt to redefine a tag definition?");
+  IsDefinition = true;
+  cast<TagType>(TypeForDecl)->decl.setPointer(this);
+  cast<TagType>(TypeForDecl)->decl.setInt(0);
+}
+
 TagDecl* TagDecl::getDefinition(ASTContext& C) const {
   QualType T = C.getTypeDeclType(const_cast<TagDecl*>(this));
   TagDecl* D = cast<TagDecl>(cast<TagType>(T)->getDecl());  
@@ -351,12 +360,7 @@ void RecordDecl::Destroy(ASTContext& C) {
 /// complete.
 void RecordDecl::completeDefinition(ASTContext& C) {
   assert(!isDefinition() && "Cannot redefine record!");
-
+  TagDecl::completeDefinition();
-  setDefinition(true);
-  
-  // Let ASTContext know that this is the defining RecordDecl for this
-  // type.
-  C.setTagDefinition(this);
 }
 
 //===----------------------------------------------------------------------===//

clang/lib/AST/DeclBase.cpp

@@ -442,37 +442,15 @@ DeclContext *DeclContext::getPrimaryContext() {
     return static_cast<NamespaceDecl*>(this)->getOriginalNamespace();
 
   case Decl::Enum:
-#if 0
-    // FIXME: See the comment for CXXRecord, below.
-    // The declaration associated with the enumeration type is our
-    // primary context.
-    return Context.getTypeDeclType(static_cast<EnumDecl*>(this))
-             ->getAsEnumType()->getDecl();
-#else
-    return this;
-#endif
-
   case Decl::Record:
-  case Decl::CXXRecord: {
+  case Decl::CXXRecord:
-    // The declaration associated with the type is be our primary
+    // If this is a tag type that has a definition or is currently
-    // context. 
+    // being defined, that definition is our primary context.
-#if 0
+    if (TagType *TagT = cast_or_null<TagType>(cast<TagDecl>(this)->TypeForDecl))
-    // FIXME: This is what we expect to do. However, it doesn't work
+      if (TagT->isBeingDefined() || 
-    // because ASTContext::setTagDefinition changes the result of
+          (TagT->getDecl() && TagT->getDecl()->isDefinition()))
-    // Context.getTypeDeclType, meaning that our "primary" declaration
+        return TagT->getDecl();
-    // of a RecordDecl/CXXRecordDecl will change, and we won't be able
-    // to find any values inserted into the earlier "primary"
-    // declaration. We need better tracking of redeclarations and
-    // definitions.
-    QualType Type = Context.getTypeDeclType(static_cast<RecordDecl*>(this));
-    return Type->getAsRecordType()->getDecl();
-#else
-    // FIXME: This hack will work for now, because the declaration we
-    // create when we're defining the record is the one we'll use as
-    // the definition later.
     return this;
-#endif
-  }
 
   case Decl::ObjCMethod:
     return this;

clang/lib/AST/TypeSerialization.cpp

@@ -258,7 +258,8 @@ Type* TagType::CreateImpl(ASTContext& Context, Deserializer& D) {
   Types.push_back(T);
   
   // Deserialize the decl.
-  T->decl = cast<TagDecl>(D.ReadOwnedPtr<Decl>(Context));
+  T->decl.setPointer(cast<TagDecl>(D.ReadOwnedPtr<Decl>(Context)));
+  T->decl.setInt(0);
 
   return T;
 }

clang/lib/Sema/Sema.h

@@ -319,7 +319,7 @@ public:
   virtual DeclTy *BuildAnonymousStructOrUnion(Scope *S, DeclSpec &DS, 
                                               RecordDecl *Record);
 
-  virtual DeclTy *ActOnTag(Scope *S, unsigned TagType, TagKind TK,
+  virtual DeclTy *ActOnTag(Scope *S, unsigned TagSpec, TagKind TK,
                            SourceLocation KWLoc, const CXXScopeSpec &SS,
                            IdentifierInfo *Name, SourceLocation NameLoc,
                            AttributeList *Attr,

clang/lib/Sema/SemaDecl.cpp

@@ -2813,9 +2813,9 @@ TypedefDecl *Sema::ParseTypedefDecl(Scope *S, Declarator &D, QualType T,
 
 /// ActOnTag - This is invoked when we see 'struct foo' or 'struct {'.  In the
 /// former case, Name will be non-null.  In the later case, Name will be null.
-/// TagType indicates what kind of tag this is. TK indicates whether this is a
+/// TagSpec indicates what kind of tag this is. TK indicates whether this is a
 /// reference/declaration/definition of a tag.
-Sema::DeclTy *Sema::ActOnTag(Scope *S, unsigned TagType, TagKind TK,
+Sema::DeclTy *Sema::ActOnTag(Scope *S, unsigned TagSpec, TagKind TK,
                              SourceLocation KWLoc, const CXXScopeSpec &SS,
                              IdentifierInfo *Name, SourceLocation NameLoc,
                              AttributeList *Attr,
@@ -2825,7 +2825,7 @@ Sema::DeclTy *Sema::ActOnTag(Scope *S, unsigned TagType, TagKind TK,
          "Nameless record must be a definition!");
   
   TagDecl::TagKind Kind;
-  switch (TagType) {
+  switch (TagSpec) {
   default: assert(0 && "Unknown tag type!");
   case DeclSpec::TST_struct: Kind = TagDecl::TK_struct; break;
   case DeclSpec::TST_union:  Kind = TagDecl::TK_union; break;
@@ -2838,6 +2838,8 @@ Sema::DeclTy *Sema::ActOnTag(Scope *S, unsigned TagType, TagKind TK,
   DeclContext *LexicalContext = CurContext;
   ScopedDecl *PrevDecl = 0;
 
+  bool Invalid = false;
+
   if (Name && SS.isNotEmpty()) {
     // We have a nested-name tag ('struct foo::bar').
 
@@ -2898,6 +2900,7 @@ Sema::DeclTy *Sema::ActOnTag(Scope *S, unsigned TagType, TagKind TK,
           // Recover by making this an anonymous redefinition.
           Name = 0;
           PrevDecl = 0;
+          Invalid = true;
         } else {
           // If this is a use, just return the declaration we found.
 
@@ -2913,12 +2916,26 @@ Sema::DeclTy *Sema::ActOnTag(Scope *S, unsigned TagType, TagKind TK,
             if (TagDecl *Def = PrevTagDecl->getDefinition(Context)) {
               Diag(NameLoc, diag::err_redefinition) << Name;
               Diag(Def->getLocation(), diag::note_previous_definition);
-              // If this is a redefinition, recover by making this struct be
+              // If this is a redefinition, recover by making this
-              // anonymous, which will make any later references get the previous
+              // struct be anonymous, which will make any later
-              // definition.
+              // references get the previous definition.
               Name = 0;
               PrevDecl = 0;
+              Invalid = true;
+            } else {
+              // If the type is currently being defined, complain
+              // about a nested redefinition.
+              TagType *Tag = cast<TagType>(Context.getTagDeclType(PrevTagDecl));
+              if (Tag->isBeingDefined()) {
+                Diag(NameLoc, diag::err_nested_redefinition) << Name;
+                Diag(PrevTagDecl->getLocation(), 
+                     diag::note_previous_definition);
+                Name = 0;
+                PrevDecl = 0;
+                Invalid = true;
+              }
             }
+
             // Okay, this is definition of a previously declared or referenced
             // tag PrevDecl. We're going to create a new Decl for it.
           }
@@ -2944,6 +2961,7 @@ Sema::DeclTy *Sema::ActOnTag(Scope *S, unsigned TagType, TagKind TK,
         Diag(PrevDecl->getLocation(), diag::note_previous_definition);
         Name = 0;
         PrevDecl = 0;
+        Invalid = true;
       } else {
         // The existing declaration isn't relevant to us; we're in a
         // new scope, so clear out the previous declaration.
@@ -3034,10 +3052,14 @@ CreateNewDecl:
       New->addAttr(new PackedAttr(Alignment * 8));
   }
 
+  if (Invalid)
+    New->setInvalidDecl();
+
   if (Attr)
     ProcessDeclAttributeList(New, Attr);
 
-  // If we're declaring or defining 
+  // If we're declaring or defining a tag in function prototype scope
+  // in C, note that this type can only be used within the function.
   if (Name && S->isFunctionPrototypeScope() && !getLangOptions().CPlusPlus)
     Diag(Loc, diag::warn_decl_in_param_list) << Context.getTagDeclType(New);
 
@@ -3045,6 +3067,9 @@ CreateNewDecl:
   // lexical context will be different from the semantic context.
   New->setLexicalDeclContext(LexicalContext);
 
+  if (TK == TK_Definition)
+    New->startDefinition();
+  
   // If this has an identifier, add it to the scope stack.
   if (Name) {
     S = getNonFieldDeclScope(S);
@@ -3332,22 +3357,6 @@ void Sema::ActOnFields(Scope* S,
   assert(EnclosingDecl && "missing record or interface decl");
   RecordDecl *Record = dyn_cast<RecordDecl>(EnclosingDecl);
   
-  if (Record) {
-    QualType RecordType = Context.getTypeDeclType(Record);
-    if (RecordType->getAsRecordType()->getDecl()->isDefinition()) {
-      RecordDecl *Def = RecordType->getAsRecordType()->getDecl();
-      // Diagnose code like:
-      //     struct S { struct S {} X; };
-      // We discover this when we complete the outer S.  Reject and ignore the
-      // outer S.
-      Diag(Def->getLocation(), diag::err_nested_redefinition)
-        << Def->getDeclName();
-      Diag(RecLoc, diag::note_previous_definition);
-      Record->setInvalidDecl();
-      return;
-    }
-  }
-  
   // Verify that all the fields are okay.
   unsigned NumNamedMembers = 0;
   llvm::SmallVector<FieldDecl*, 32> RecFields;
@@ -3564,19 +3573,6 @@ void Sema::ActOnEnumBody(SourceLocation EnumLoc, DeclTy *EnumDeclX,
   EnumDecl *Enum = cast<EnumDecl>(static_cast<Decl*>(EnumDeclX));
   QualType EnumType = Context.getTypeDeclType(Enum);
   
-  if (EnumType->getAsEnumType()->getDecl()->isDefinition()) {
-    EnumDecl *Def = EnumType->getAsEnumType()->getDecl();
-    // Diagnose code like:
-    //   enum e0 {
-    //     E0 = sizeof(enum e0 { E1 })
-    //   };
-    Diag(Def->getLocation(), diag::err_nested_redefinition)
-      << Enum->getDeclName();
-    Diag(Enum->getLocation(), diag::note_previous_definition);
-    Enum->setInvalidDecl();
-    return;
-  }
-
   // TODO: If the result value doesn't fit in an int, it must be a long or long
   // long value.  ISO C does not support this, but GCC does as an extension,
   // emit a warning.

clang/lib/Sema/SemaLookup.cpp

@@ -625,6 +625,7 @@ bool Sema::DiagnoseAmbiguousLookup(LookupResult &Result, DeclarationName Name,
       ++Found;
 
     Diag((*Found)->getLocation(), diag::note_ambiguous_member_found);
+
     return true;
   } 
 

clang/test/Sema/enum.c

@@ -1,5 +1,4 @@
 // RUN: clang %s -fsyntax-only -verify -pedantic
-
 enum e {A, 
         B = 42LL << 32,        // expected-warning {{ISO C restricts enumerator values to range of 'int'}}
       C = -4, D = 12456 };

clang/test/SemaCXX/qualified-id-lookup.cpp

@@ -44,7 +44,10 @@ namespace N {
   }
 }
 
-void N::f1::foo(int) { }
+void N::f1::foo(int i) { 
+  f1::member = i; 
+  f1::type &ir = i;
+}
 
 namespace N {
   float& f1(int x) {
@@ -93,4 +96,17 @@ void test_a() {
   a::a::a::i = 4;
 }
   
+struct Undef {
+  typedef int type;
+
+  Undef::type member;
+
+  static int size = sizeof(Undef); // expected-error{{invalid application of 'sizeof' to an incomplete type 'struct Undef'}}
+
+  int f();
+};
+
+int Undef::f() {
+  return sizeof(Undef);
+}