[clang] Implement divergence for TypedefType and UsingType

With this patch, TypedefTypes and UsingTypes can have an
underlying type which diverges from their corresponding
declarations.

For the TypedefType case, this can be seen when getting
the common sugared type between two redeclarations with
different sugar.

For both cases, this will become important as resugaring
is implemented, as this will allow us to resugar these
when they were dependent before instantiation.

Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>

Differential Revision: https://reviews.llvm.org/D133468

Author: mizvekov

clang/include/clang/AST/ASTContext.h

@@ -246,6 +246,7 @@ class ASTContext : public RefCountedBase<ASTContext> {
     TemplateSpecializationTypes;
   mutable llvm::FoldingSet<ParenType> ParenTypes{GeneralTypesLog2InitSize};
   mutable llvm::FoldingSet<UsingType> UsingTypes;
+  mutable llvm::FoldingSet<TypedefType> TypedefTypes;
   mutable llvm::FoldingSet<ElaboratedType> ElaboratedTypes{
       GeneralTypesLog2InitSize};
   mutable llvm::FoldingSet<DependentNameType> DependentNameTypes;

clang/include/clang/AST/JSONNodeDumper.h

@@ -209,6 +209,7 @@ class JSONNodeDumper
   void Visit(const APValue &Value, QualType Ty);
 
   void VisitTypedefType(const TypedefType *TT);
+  void VisitUsingType(const UsingType *TT);
   void VisitFunctionType(const FunctionType *T);
   void VisitFunctionProtoType(const FunctionProtoType *T);
   void VisitRValueReferenceType(const ReferenceType *RT);

clang/include/clang/AST/Type.h

@@ -1807,6 +1807,24 @@ class alignas(8) Type : public ExtQualsTypeCommonBase {
     unsigned IsUnqual : 1; // If true: typeof_unqual, else: typeof
   };
 
+  class UsingBitfields {
+    friend class UsingType;
+
+    unsigned : NumTypeBits;
+
+    /// True if the underlying type is different from the declared one.
+    unsigned hasTypeDifferentFromDecl : 1;
+  };
+
+  class TypedefBitfields {
+    friend class TypedefType;
+
+    unsigned : NumTypeBits;
+
+    /// True if the underlying type is different from the declared one.
+    unsigned hasTypeDifferentFromDecl : 1;
+  };
+
   class SubstTemplateTypeParmTypeBitfields {
     friend class SubstTemplateTypeParmType;
 
@@ -1897,6 +1915,8 @@ class alignas(8) Type : public ExtQualsTypeCommonBase {
     AttributedTypeBitfields AttributedTypeBits;
     AutoTypeBitfields AutoTypeBits;
     TypeOfBitfields TypeOfBits;
+    TypedefBitfields TypedefBits;
+    UsingBitfields UsingBits;
     BuiltinTypeBitfields BuiltinTypeBits;
     FunctionTypeBitfields FunctionTypeBits;
     ObjCObjectTypeBitfields ObjCObjectTypeBits;
@@ -4476,9 +4496,12 @@ class UnresolvedUsingType : public Type {
   }
 };
 
-class UsingType : public Type, public llvm::FoldingSetNode {
+class UsingType final : public Type,
+                        public llvm::FoldingSetNode,
+                        private llvm::TrailingObjects<UsingType, QualType> {
   UsingShadowDecl *Found;
   friend class ASTContext; // ASTContext creates these.
+  friend TrailingObjects;
 
   UsingType(const UsingShadowDecl *Found, QualType Underlying, QualType Canon);
 
@@ -4487,21 +4510,31 @@ class UsingType : public Type, public llvm::FoldingSetNode {
   QualType getUnderlyingType() const;
 
   bool isSugared() const { return true; }
+
+  // This always has the 'same' type as declared, but not necessarily identical.
   QualType desugar() const { return getUnderlyingType(); }
 
-  void Profile(llvm::FoldingSetNodeID &ID) { Profile(ID, Found); }
-  static void Profile(llvm::FoldingSetNodeID &ID,
-                      const UsingShadowDecl *Found) {
+  // Internal helper, for debugging purposes.
+  bool typeMatchesDecl() const { return !UsingBits.hasTypeDifferentFromDecl; }
+
+  void Profile(llvm::FoldingSetNodeID &ID) {
+    Profile(ID, Found, typeMatchesDecl() ? QualType() : getUnderlyingType());
+  }
+  static void Profile(llvm::FoldingSetNodeID &ID, const UsingShadowDecl *Found,
+                      QualType Underlying) {
     ID.AddPointer(Found);
+    if (!Underlying.isNull())
+      Underlying.Profile(ID);
   }
   static bool classof(const Type *T) { return T->getTypeClass() == Using; }
 };
 
-class TypedefType : public Type {
+class TypedefType final : public Type,
+                          public llvm::FoldingSetNode,
+                          private llvm::TrailingObjects<TypedefType, QualType> {
   TypedefNameDecl *Decl;
-
-private:
   friend class ASTContext; // ASTContext creates these.
+  friend TrailingObjects;
 
   TypedefType(TypeClass tc, const TypedefNameDecl *D, QualType underlying,
               QualType can);
@@ -4510,8 +4543,23 @@ class TypedefType : public Type {
   TypedefNameDecl *getDecl() const { return Decl; }
 
   bool isSugared() const { return true; }
+
+  // This always has the 'same' type as declared, but not necessarily identical.
   QualType desugar() const;
 
+  // Internal helper, for debugging purposes.
+  bool typeMatchesDecl() const { return !TypedefBits.hasTypeDifferentFromDecl; }
+
+  void Profile(llvm::FoldingSetNodeID &ID) {
+    Profile(ID, Decl, typeMatchesDecl() ? QualType() : desugar());
+  }
+  static void Profile(llvm::FoldingSetNodeID &ID, const TypedefNameDecl *Decl,
+                      QualType Underlying) {
+    ID.AddPointer(Decl);
+    if (!Underlying.isNull())
+      Underlying.Profile(ID);
+  }
+
   static bool classof(const Type *T) { return T->getTypeClass() == Typedef; }
 };
 

clang/include/clang/AST/TypeProperties.td

@@ -379,16 +379,12 @@ let Class = TypedefType in {
   def : Property<"declaration", DeclRef> {
     let Read = [{ node->getDecl() }];
   }
-  def : Property<"canonicalType", Optional<QualType>> {
-    let Read = [{ makeOptionalFromNullable(node->getCanonicalTypeInternal()) }];
+  def : Property<"underlyingType", QualType> {
+    let Read = [{ node->desugar() }];
   }
 
   def : Creator<[{
-    QualType finalCanonicalType =
-      canonicalType ? ctx.getCanonicalType(*canonicalType)
-                    : QualType();
-    return ctx.getTypedefType(cast<TypedefNameDecl>(declaration),
-                              finalCanonicalType);
+    return ctx.getTypedefType(cast<TypedefNameDecl>(declaration), underlyingType);
   }]>;
 }
 

clang/lib/AST/ASTContext.cpp

@@ -2364,12 +2364,12 @@ TypeInfo ASTContext::getTypeInfoImpl(const Type *T) const {
     return getTypeInfo(cast<UsingType>(T)->desugar().getTypePtr());
 
   case Type::Typedef: {
-    const TypedefNameDecl *Typedef = cast<TypedefType>(T)->getDecl();
-    TypeInfo Info = getTypeInfo(Typedef->getUnderlyingType().getTypePtr());
+    const auto *TT = cast<TypedefType>(T);
+    TypeInfo Info = getTypeInfo(TT->desugar().getTypePtr());
     // If the typedef has an aligned attribute on it, it overrides any computed
     // alignment we have.  This violates the GCC documentation (which says that
     // attribute(aligned) can only round up) but matches its implementation.
-    if (unsigned AttrAlign = Typedef->getMaxAlignment()) {
+    if (unsigned AttrAlign = TT->getDecl()->getMaxAlignment()) {
       Align = AttrAlign;
       AlignRequirement = AlignRequirementKind::RequiredByTypedef;
     } else {
@@ -4638,34 +4638,60 @@ QualType ASTContext::getTypeDeclTypeSlow(const TypeDecl *Decl) const {
 /// specified typedef name decl.
 QualType ASTContext::getTypedefType(const TypedefNameDecl *Decl,
                                     QualType Underlying) const {
-  if (Decl->TypeForDecl) return QualType(Decl->TypeForDecl, 0);
+  if (!Decl->TypeForDecl) {
+    if (Underlying.isNull())
+      Underlying = Decl->getUnderlyingType();
+    auto *NewType = new (*this, TypeAlignment) TypedefType(
+        Type::Typedef, Decl, QualType(), getCanonicalType(Underlying));
+    Decl->TypeForDecl = NewType;
+    Types.push_back(NewType);
+    return QualType(NewType, 0);
+  }
+  if (Underlying.isNull() || Decl->getUnderlyingType() == Underlying)
+    return QualType(Decl->TypeForDecl, 0);
+  assert(hasSameType(Decl->getUnderlyingType(), Underlying));
 
-  if (Underlying.isNull())
-    Underlying = Decl->getUnderlyingType();
-  QualType Canonical = getCanonicalType(Underlying);
-  auto *newType = new (*this, TypeAlignment)
-      TypedefType(Type::Typedef, Decl, Underlying, Canonical);
-  Decl->TypeForDecl = newType;
-  Types.push_back(newType);
-  return QualType(newType, 0);
+  llvm::FoldingSetNodeID ID;
+  TypedefType::Profile(ID, Decl, Underlying);
+
+  void *InsertPos = nullptr;
+  if (TypedefType *T = TypedefTypes.FindNodeOrInsertPos(ID, InsertPos)) {
+    assert(!T->typeMatchesDecl() &&
+           "non-divergent case should be handled with TypeDecl");
+    return QualType(T, 0);
+  }
+
+  void *Mem =
+      Allocate(TypedefType::totalSizeToAlloc<QualType>(true), TypeAlignment);
+  auto *NewType = new (Mem) TypedefType(Type::Typedef, Decl, Underlying,
+                                        getCanonicalType(Underlying));
+  TypedefTypes.InsertNode(NewType, InsertPos);
+  Types.push_back(NewType);
+  return QualType(NewType, 0);
 }
 
 QualType ASTContext::getUsingType(const UsingShadowDecl *Found,
                                   QualType Underlying) const {
   llvm::FoldingSetNodeID ID;
-  UsingType::Profile(ID, Found);
+  UsingType::Profile(ID, Found, Underlying);
 
   void *InsertPos = nullptr;
-  UsingType *T = UsingTypes.FindNodeOrInsertPos(ID, InsertPos);
-  if (T)
+  if (UsingType *T = UsingTypes.FindNodeOrInsertPos(ID, InsertPos))
     return QualType(T, 0);
 
-  assert(!Underlying.hasLocalQualifiers());
-  assert(Underlying == getTypeDeclType(cast<TypeDecl>(Found->getTargetDecl())));
-  QualType Canon = Underlying.getCanonicalType();
+  const Type *TypeForDecl =
+      cast<TypeDecl>(Found->getTargetDecl())->getTypeForDecl();
 
-  UsingType *NewType =
-      new (*this, TypeAlignment) UsingType(Found, Underlying, Canon);
+  assert(!Underlying.hasLocalQualifiers());
+  QualType Canon = Underlying->getCanonicalTypeInternal();
+  assert(TypeForDecl->getCanonicalTypeInternal() == Canon);
+
+  if (Underlying.getTypePtr() == TypeForDecl)
+    Underlying = QualType();
+  void *Mem =
+      Allocate(UsingType::totalSizeToAlloc<QualType>(!Underlying.isNull()),
+               TypeAlignment);
+  UsingType *NewType = new (Mem) UsingType(Found, Underlying, Canon);
   Types.push_back(NewType);
   UsingTypes.InsertNode(NewType, InsertPos);
   return QualType(NewType, 0);

clang/lib/AST/ASTImporter.cpp

@@ -1362,8 +1362,12 @@ ExpectedType ASTNodeImporter::VisitTypedefType(const TypedefType *T) {
   Expected<TypedefNameDecl *> ToDeclOrErr = import(T->getDecl());
   if (!ToDeclOrErr)
     return ToDeclOrErr.takeError();
+  ExpectedType ToUnderlyingTypeOrErr = import(T->desugar());
+  if (!ToUnderlyingTypeOrErr)
+    return ToUnderlyingTypeOrErr.takeError();
 
-  return Importer.getToContext().getTypeDeclType(*ToDeclOrErr);
+  return Importer.getToContext().getTypedefType(*ToDeclOrErr,
+                                                *ToUnderlyingTypeOrErr);
 }
 
 ExpectedType ASTNodeImporter::VisitTypeOfExprType(const TypeOfExprType *T) {

clang/lib/AST/ASTStructuralEquivalence.cpp

@@ -957,11 +957,17 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
     if (!IsStructurallyEquivalent(Context, cast<UsingType>(T1)->getFoundDecl(),
                                   cast<UsingType>(T2)->getFoundDecl()))
       return false;
+    if (!IsStructurallyEquivalent(Context,
+                                  cast<UsingType>(T1)->getUnderlyingType(),
+                                  cast<UsingType>(T2)->getUnderlyingType()))
+      return false;
     break;
 
   case Type::Typedef:
     if (!IsStructurallyEquivalent(Context, cast<TypedefType>(T1)->getDecl(),
-                                  cast<TypedefType>(T2)->getDecl()))
+                                  cast<TypedefType>(T2)->getDecl()) ||
+        !IsStructurallyEquivalent(Context, cast<TypedefType>(T1)->desugar(),
+                                  cast<TypedefType>(T2)->desugar()))
       return false;
     break;
 

clang/lib/AST/JSONNodeDumper.cpp

@@ -530,6 +530,14 @@ JSONNodeDumper::createCXXBaseSpecifier(const CXXBaseSpecifier &BS) {
 
 void JSONNodeDumper::VisitTypedefType(const TypedefType *TT) {
   JOS.attribute("decl", createBareDeclRef(TT->getDecl()));
+  if (!TT->typeMatchesDecl())
+    JOS.attribute("type", createQualType(TT->desugar()));
+}
+
+void JSONNodeDumper::VisitUsingType(const UsingType *TT) {
+  JOS.attribute("decl", createBareDeclRef(TT->getFoundDecl()));
+  if (!TT->typeMatchesDecl())
+    JOS.attribute("type", createQualType(TT->desugar()));
 }
 
 void JSONNodeDumper::VisitFunctionType(const FunctionType *T) {

clang/lib/AST/TextNodeDumper.cpp

@@ -1543,10 +1543,14 @@ void TextNodeDumper::VisitUnresolvedUsingType(const UnresolvedUsingType *T) {
 
 void TextNodeDumper::VisitUsingType(const UsingType *T) {
   dumpDeclRef(T->getFoundDecl());
+  if (!T->typeMatchesDecl())
+    OS << " divergent";
 }
 
 void TextNodeDumper::VisitTypedefType(const TypedefType *T) {
   dumpDeclRef(T->getDecl());
+  if (!T->typeMatchesDecl())
+    OS << " divergent";
 }
 
 void TextNodeDumper::VisitUnaryTransformType(const UnaryTransformType *T) {

clang/lib/AST/Type.cpp

@@ -3434,25 +3434,34 @@ void FunctionProtoType::Profile(llvm::FoldingSetNodeID &ID,
 }
 
 TypedefType::TypedefType(TypeClass tc, const TypedefNameDecl *D,
-                         QualType underlying, QualType can)
-    : Type(tc, can, toSemanticDependence(underlying->getDependence())),
+                         QualType Underlying, QualType can)
+    : Type(tc, can, toSemanticDependence(can->getDependence())),
       Decl(const_cast<TypedefNameDecl *>(D)) {
   assert(!isa<TypedefType>(can) && "Invalid canonical type");
+  TypedefBits.hasTypeDifferentFromDecl = !Underlying.isNull();
+  if (!typeMatchesDecl())
+    *getTrailingObjects<QualType>() = Underlying;
 }
 
 QualType TypedefType::desugar() const {
-  return getDecl()->getUnderlyingType();
+  return typeMatchesDecl() ? Decl->getUnderlyingType()
+                           : *getTrailingObjects<QualType>();
 }
 
 UsingType::UsingType(const UsingShadowDecl *Found, QualType Underlying,
                      QualType Canon)
-    : Type(Using, Canon, toSemanticDependence(Underlying->getDependence())),
+    : Type(Using, Canon, toSemanticDependence(Canon->getDependence())),
       Found(const_cast<UsingShadowDecl *>(Found)) {
-  assert(Underlying == getUnderlyingType());
+  UsingBits.hasTypeDifferentFromDecl = !Underlying.isNull();
+  if (!typeMatchesDecl())
+    *getTrailingObjects<QualType>() = Underlying;
 }
 
 QualType UsingType::getUnderlyingType() const {
-  return QualType(cast<TypeDecl>(Found->getTargetDecl())->getTypeForDecl(), 0);
+  return typeMatchesDecl()
+             ? QualType(
+                   cast<TypeDecl>(Found->getTargetDecl())->getTypeForDecl(), 0)
+             : *getTrailingObjects<QualType>();
 }
 
 QualType MacroQualifiedType::desugar() const { return getUnderlyingType(); }

clang/test/SemaCXX/sugar-common-types.cpp

@@ -112,3 +112,22 @@ C1<X2> auto t26_2 = (::SB1){};
 C2<X2> auto t26_3 = (::SB1){};
 N t26 = 0 ? t26_1 : t26_2; // expected-error {{from 'SB1' (aka 'SS1')}}
 N t27 = 0 ? t26_1 : t26_3; // expected-error {{from 'SB1' (aka 'SS1')}}
+
+using RPB1 = X1*;
+using RPX1 = RPB1;
+using RPB1 = Y1*; // redeclared
+using RPY1 = RPB1;
+N t28 = *(RPB1){}; // expected-error {{lvalue of type 'Y1' (aka 'int')}}
+auto t29 = 0 ? (RPX1){} : (RPY1){};
+N t30 = t29;  // expected-error {{lvalue of type 'RPB1' (aka 'int *')}}
+N t31 = *t29; // expected-error {{lvalue of type 'B1' (aka 'int')}}
+
+namespace A { using type1 = X1*; };
+namespace C { using A::type1; };
+using UPX1 = C::type1;
+namespace A { using type1 = Y1*; };  // redeclared
+namespace C { using A::type1; };     // redeclared
+using UPY1 = C::type1;
+auto t32 = 0 ? (UPX1){} : (UPY1){};
+N t33 = t32;  // expected-error {{lvalue of type 'C::type1' (aka 'int *')}}
+N t34 = *t32; // expected-error {{lvalue of type 'B1' (aka 'int')}}