Null reflections.

Closes issue #46.

clang/include/clang/AST/ExprCXX.h

@@ -5329,6 +5329,7 @@ class CXXReflectExpr : public Expr {
   SourceLocation OpLoc;
   SourceLocation ArgLoc;
 
+  CXXReflectExpr(const ASTContext &C, QualType T);
   CXXReflectExpr(const ASTContext &C, QualType T, QualType Arg);
   CXXReflectExpr(const ASTContext &C, QualType T, Expr *Arg);
   CXXReflectExpr(const ASTContext &C, QualType T, Decl *Arg, bool IsNamespace);
@@ -5337,6 +5338,8 @@ class CXXReflectExpr : public Expr {
   CXXReflectExpr(const ASTContext &C, QualType T, TagDataMemberSpec *Arg);
 
 public:
+  static CXXReflectExpr *Create(ASTContext &C, SourceLocation OperatorLoc,
+                                SourceLocation OperandLoc);
   static CXXReflectExpr *Create(ASTContext &C, SourceLocation OperatorLoc,
                                 SourceLocation ArgLoc, QualType Operand);
   static CXXReflectExpr *Create(ASTContext &C, SourceLocation OperatorLoc,

clang/include/clang/AST/PropertiesBase.td

@@ -265,6 +265,11 @@ class PropertyTypeCase<PropertyType type, string name> : HasProperties {
 // Type cases for ReflectionValue.
 def : PropertyTypeKind<ReflectionValue, ReflectionKind,
                        "node.getKind()">;
+let Class = PropertyTypeCase<ReflectionValue, "RK_null"> in {
+  def : Creator<[{
+    return ReflectionValue();
+  }]>;
+}
 let Class = PropertyTypeCase<ReflectionValue, "RK_type"> in {
   def : Property<"value", QualType> {
     let Read = [{ node.getAsType() }];

clang/include/clang/AST/RecursiveASTVisitor.h

@@ -2970,6 +2970,7 @@ DEF_TRAVERSE_STMT(CXXReflectExpr, {
     TRY_TO(TraverseDecl(Op.getAsNamespace()));
     break;
   }
+  case ReflectionValue::RK_null:
   case ReflectionValue::RK_base_specifier:
   case ReflectionValue::RK_data_member_spec:
     break;

clang/include/clang/AST/Reflection.h

@@ -38,6 +38,9 @@ class ReflectionValue {
 public:
   /// \brief The kind of construct reflected.
   enum ReflectionKind {
+    /// \brief A null reflection. Corresponds to no object.
+    RK_null = 0,
+
     /// \brief A reflection of a type. Corresponds to an object of type
     /// QualType.
     RK_type = 1,
@@ -86,7 +89,7 @@ class ReflectionValue {
   void *Entity;
 
 public:
-  ReflectionValue() = default;
+  ReflectionValue();
   ReflectionValue(ReflectionValue const&Rhs);
   ReflectionValue(ReflectionKind ReflKind, void *Entity);
   ReflectionValue &operator=(ReflectionValue const& Rhs);
@@ -98,6 +101,9 @@ class ReflectionValue {
     return Entity;
   }
 
+  /// Returns whether this is a null reflection.
+  bool isNull() const;
+
   /// Returns this as a type operand.
   QualType getAsType() const;
 

clang/lib/AST/APValue.cpp

@@ -996,6 +996,9 @@ void APValue::printPretty(raw_ostream &Out, const PrintingPolicy &Policy,
     const ReflectionValue& Refl = getReflection();
     std::string Repr("...");
     switch (Refl.getKind()) {
+    case ReflectionValue::RK_null:
+      Repr = "null";
+      break;
     case ReflectionValue::RK_type:
       Repr = "type";
       break;

clang/lib/AST/ComputeDependence.cpp

@@ -965,6 +965,7 @@ ExprDependence clang::computeDependence(CXXReflectExpr *E,
       D |= ExprDependence::UnexpandedPack;
     return D | computeDeclDependence(VD, Ctx);
   }
+  case ReflectionValue::RK_null:
   case ReflectionValue::RK_namespace:
   case ReflectionValue::RK_base_specifier:
   case ReflectionValue::RK_data_member_spec:

clang/lib/AST/ExprCXX.cpp

@@ -1842,6 +1842,11 @@ TypeTraitExpr *TypeTraitExpr::CreateDeserialized(const ASTContext &C,
   return new (Mem) TypeTraitExpr(EmptyShell());
 }
 
+CXXReflectExpr::CXXReflectExpr(const ASTContext &C, QualType T)
+    : Expr(CXXReflectExprClass, T, VK_PRValue, OK_Ordinary), Ref() {
+  setDependence(computeDependence(this, C));
+}
+
 CXXReflectExpr::CXXReflectExpr(const ASTContext &C, QualType T,
                                QualType Operand)
     : Expr(CXXReflectExprClass, T, VK_PRValue, OK_Ordinary),
@@ -1885,6 +1890,15 @@ CXXReflectExpr::CXXReflectExpr(const ASTContext &C, QualType T,
   setDependence(computeDependence(this, C));
 }
 
+CXXReflectExpr *CXXReflectExpr::Create(ASTContext &C,
+                                       SourceLocation OperatorLoc,
+                                       SourceLocation OperandLoc) {
+  CXXReflectExpr *E = new (C) CXXReflectExpr(C, C.MetaInfoTy);
+  E->setOperatorLoc(OperatorLoc);
+  E->setArgLoc(OperandLoc);
+  return E;
+}
+
 CXXReflectExpr *CXXReflectExpr::Create(ASTContext &C,
                                        SourceLocation OperatorLoc,
                                        SourceLocation OperandLoc,

clang/lib/AST/ExprConstant.cpp

@@ -15777,6 +15777,15 @@ class ReflectionEvaluator
     return true;
   }
 
+  bool ZeroInitialization(const Expr *E) {
+    Result = APValue(ReflectionValue::RK_null, nullptr);
+    return true;
+  }
+
+  bool VisitImplicitValueInitExpr(const ImplicitValueInitExpr *E) {
+    return ZeroInitialization(E);
+  }
+
   bool VisitCXXReflectExpr(const CXXReflectExpr *E);
   bool VisitCXXMetafunctionExpr(const CXXMetafunctionExpr *E);
   bool VisitCXXIndeterminateSpliceExpr(const CXXIndeterminateSpliceExpr *E);
@@ -15786,6 +15795,10 @@ class ReflectionEvaluator
 bool ReflectionEvaluator::VisitCXXReflectExpr(const CXXReflectExpr *E) {
   const ReflectionValue &Ref = E->getOperand();
   switch (Ref.getKind()) {
+  case ReflectionValue::RK_null: {
+    APValue Result(ReflectionValue::RK_null, nullptr);
+    return Success(Result, E);
+  }
   case ReflectionValue::RK_type: {
     APValue Result(ReflectionValue::RK_type, Ref.getAsType().getAsOpaquePtr());
     return Success(Result, E);

clang/lib/AST/ItaniumMangle.cpp

@@ -4672,6 +4672,9 @@ void CXXNameMangler::mangleReflection(const ReflectionValue &R) {
   Out << 'M';
 
   switch (R.getKind()) {
+  case ReflectionValue::RK_null:
+    Out << '0';
+    break;
   case ReflectionValue::RK_type: {
     Out << 't';
     QualType QT = R.getAsType();

clang/lib/AST/MicrosoftMangle.cpp

@@ -2031,6 +2031,9 @@ void MicrosoftCXXNameMangler::mangleReflection(const ReflectionValue &R) {
 
   const void *opaque = R.getOpaqueValue();
   switch (R.getKind()) {
+  case ReflectionValue::RK_null:
+    Out << '0';
+    break;
   case ReflectionValue::RK_type: {
     Out << 't';
     QualType QT = QualType::getFromOpaquePtr(opaque);

clang/lib/AST/Reflection.cpp

@@ -22,6 +22,8 @@
 
 namespace clang {
 
+ReflectionValue::ReflectionValue() : Kind(RK_null), Entity(nullptr) { }
+
 ReflectionValue::ReflectionValue(ReflectionKind Kind, void *Entity)
     : Kind(Kind), Entity(Entity) {
 }
@@ -37,6 +39,8 @@ ReflectionValue &ReflectionValue::operator=(ReflectionValue const&Rhs) {
   return *this;
 }
 
+bool ReflectionValue::isNull() const { return Kind == RK_null; }
+
 QualType ReflectionValue::getAsType() const {
   assert(getKind() == RK_type && "not a type");
 
@@ -68,6 +72,8 @@ QualType ReflectionValue::getAsType() const {
 void ReflectionValue::Profile(llvm::FoldingSetNodeID &ID) const {
   ID.AddInteger(Kind);
   switch (Kind) {
+  case RK_null:
+    break;
   case RK_type: {
     QualType QT = getAsType();
     QT.Profile(ID);
@@ -115,6 +121,8 @@ bool ReflectionValue::operator==(ReflectionValue const& Rhs) const {
     return false;
 
   switch (getKind()) {
+  case RK_null:
+    return true;
   case RK_type: {
     QualType LQT = getAsType(), RQT = Rhs.getAsType();
     if (LQT.getQualifiers() != RQT.getQualifiers())