ObjC: Use a new type for ObjC type parameter (Patch 1 out of 3)

[manmanren]

Summary

For ObjC type parameter, we used to have TypedefType that is canonicalized to
id or the bound type. We can't represent "T <protocol>" and thus will lose
the type information in the following example:
@interface MyMutableDictionary<KeyType, ObjectType> : NSObject

• (void)setObject:(ObjectType)obj forKeyedSubscript:(KeyType <NSCopying>)key;

@end
MyMutableDictionary<NSString *, NSString *> *stringsByString;
NSNumber *n1, *n2;
stringsByString[n1] = n2;
--> no warning on type mismatch of the key.

To fix the problem, we introduce a new type ObjCTypeParamType that supports
a list of protocol qualifiers.

This is the first patch:
[NFC] Add a class ObjCProtocolQualifiers to wrap APIs for ObjC protocol list.
This will be shared between ObjCObjectType and ObjCTypeParamType.

[doug.gregor]

This refactor LGTM.

include/clang/AST/Type.h

if (NumExpansions)
       ID.AddInteger(*NumExpansions);
   }
 
   static bool classof(const Type *T) {
     return T->getTypeClass() == PackExpansion;
   }
 };
 
+/// This class wraps the list of protocol qualifiers. For types that can
+/// take ObjC protocol qualifers, they can subclass this class. This class
+/// saves the number of protocols
+template <class T>
+class ObjCProtocolQualifiers {
+protected:
+  ObjCProtocolQualifiers() {}
+  ObjCProtocolDecl * const *getProtocolStorage() const {
+    return const_cast<ObjCProtocolQualifiers*>(this)->getProtocolStorage();
+  }
+
+  ObjCProtocolDecl **getProtocolStorage() {
+    return static_cast<T*>(this)->getProtocolStorageImpl();
+  }
+  void setNumProtocols(unsigned N) {
+    static_cast<T*>(this)->setNumProtocolsImpl(N);
+  }
+  void initialize(ArrayRef<ObjCProtocolDecl *> protocols) {
+    setNumProtocols(protocols.size());
+    assert(getNumProtocols() == protocols.size() &&
+           "bitfield overflow in protocol count");
+    if (!protocols.empty())
+      memcpy(getProtocolStorage(), protocols.data(),
+             protocols.size() * sizeof(ObjCProtocolDecl*));
+  }
+
+public:
+  typedef ObjCProtocolDecl * const *qual_iterator;
+  typedef llvm::iterator_range<qual_iterator> qual_range;
+
+  qual_range quals() const { return qual_range(qual_begin(), qual_end()); }
+  qual_iterator qual_begin() const { return getProtocolStorage(); }
+  qual_iterator qual_end() const { return qual_begin() + getNumProtocols(); }
+
+  bool qual_empty() const { return getNumProtocols() == 0; }
+
+  /// Return the number of qualifying protocols in this type, or 0 if
+  /// there are none.
+  unsigned getNumProtocols() const {
+    return static_cast<const T*>(this)->getNumProtocolsImpl();
+  }
+
+  /// Fetch a protocol by index.
+  ObjCProtocolDecl *getProtocol(unsigned I) const {
+    assert(I < getNumProtocols() && "Out-of-range protocol access");
+    return qual_begin()[I];
+  }
+
+  /// Retrieve all of the protocol qualifiers.
+  ArrayRef<ObjCProtocolDecl *> getProtocols() const {
+    return ArrayRef<ObjCProtocolDecl *>(qual_begin(), getNumProtocols());
+  }
+};
+
 /// Represents a class type in Objective C.
 ///
 /// Every Objective C type is a combination of a base type, a set of
 /// type arguments (optional, for parameterized classes) and a list of
 /// protocols.
 ///
 /// Given the following declarations:
 /// \code

 ///
 /// 'id' is a TypedefType which is sugar for an ObjCObjectPointerType whose
 /// pointee is an ObjCObjectType with base BuiltinType::ObjCIdType
 /// and no protocols.
 ///
 /// 'id<P>' is an ObjCObjectPointerType whose pointee is an ObjCObjectType
 /// with base BuiltinType::ObjCIdType and protocol list [P].  Eventually
 /// this should get its own sugar class to better represent the source.
-class ObjCObjectType : public Type {
+class ObjCObjectType : public Type,
+                       public ObjCProtocolQualifiers<ObjCObjectType> {
+  friend class ObjCProtocolQualifiers;
   // ObjCObjectType.NumTypeArgs - the number of type arguments stored
   // after the ObjCObjectPointerType node.
   // ObjCObjectType.NumProtocols - the number of protocols stored
   // after the type arguments of ObjCObjectPointerType node.
   //
   // These protocols are those written directly on the type.  If
   // protocol qualifiers ever become additive, the iterators will need
   // to get kindof complicated.
   //
   // In the canonical object type, these are sorted alphabetically
   // and uniqued.
 
   /// Either a BuiltinType or an InterfaceType or sugar for either.
   QualType BaseType;
 
   /// Cached superclass type.
   mutable llvm::PointerIntPair<const ObjCObjectType *, 1, bool>
     CachedSuperClassType;
 
-  ObjCProtocolDecl * const *getProtocolStorage() const {
-    return const_cast<ObjCObjectType*>(this)->getProtocolStorage();
-  }
-
   QualType *getTypeArgStorage();
   const QualType *getTypeArgStorage() const {
     return const_cast<ObjCObjectType *>(this)->getTypeArgStorage();
   }
 
-  ObjCProtocolDecl **getProtocolStorage();
+  ObjCProtocolDecl **getProtocolStorageImpl();
+  /// Return the number of qualifying protocols in this interface type,
+  /// or 0 if there are none.
+  unsigned getNumProtocolsImpl() const {
+    return ObjCObjectTypeBits.NumProtocols;
+  }
+  void setNumProtocolsImpl(unsigned N) {
+    ObjCObjectTypeBits.NumProtocols = N;
+  }
 
 protected:
   ObjCObjectType(QualType Canonical, QualType Base,
                  ArrayRef<QualType> typeArgs,
                  ArrayRef<ObjCProtocolDecl *> protocols,
                  bool isKindOf);
 
   enum Nonce_ObjCInterface { Nonce_ObjCInterface };
public:
 
   /// Retrieve the type arguments of this object type as they were
   /// written.
   ArrayRef<QualType> getTypeArgsAsWritten() const {
     return llvm::makeArrayRef(getTypeArgStorage(),
                               ObjCObjectTypeBits.NumTypeArgs);
   }
 
-  typedef ObjCProtocolDecl * const *qual_iterator;
-  typedef llvm::iterator_range<qual_iterator> qual_range;
-
-  qual_range quals() const { return qual_range(qual_begin(), qual_end()); }
-  qual_iterator qual_begin() const { return getProtocolStorage(); }
-  qual_iterator qual_end() const { return qual_begin() + getNumProtocols(); }
-
-  bool qual_empty() const { return getNumProtocols() == 0; }
-
-  /// Return the number of qualifying protocols in this interface type,
-  /// or 0 if there are none.
-  unsigned getNumProtocols() const { return ObjCObjectTypeBits.NumProtocols; }
-
-  /// Fetch a protocol by index.
-  ObjCProtocolDecl *getProtocol(unsigned I) const {
-    assert(I < getNumProtocols() && "Out-of-range protocol access");
-    return qual_begin()[I];
-  }
-
-  /// Retrieve all of the protocol qualifiers.
-  ArrayRef<ObjCProtocolDecl *> getProtocols() const {
-    return ArrayRef<ObjCProtocolDecl *>(qual_begin(), getNumProtocols());
-  }
-
   /// Whether this is a "__kindof" type as written.
   bool isKindOfTypeAsWritten() const { return ObjCObjectTypeBits.IsKindOf; }
 
   /// Whether this ia a "__kindof" type (semantically).
   bool isKindOfType() const;
 
   /// Retrieve the type of the superclass of this object type.
   ///
static void Profile(llvm::FoldingSetNodeID &ID,
                       ArrayRef<ObjCProtocolDecl *> protocols,
                       bool isKindOf);
 };
 
 inline QualType *ObjCObjectType::getTypeArgStorage() {
   return reinterpret_cast<QualType *>(static_cast<ObjCObjectTypeImpl*>(this)+1);
 }
 
-inline ObjCProtocolDecl **ObjCObjectType::getProtocolStorage() {
+inline ObjCProtocolDecl **ObjCObjectType::getProtocolStorageImpl() {
     return reinterpret_cast<ObjCProtocolDecl**>(
              getTypeArgStorage() + ObjCObjectTypeBits.NumTypeArgs);
 }
 
 /// Interfaces are the core concept in Objective-C for object oriented design.
 /// They basically correspond to C++ classes.  There are two kinds of interface
 /// types: normal interfaces like `NSString`, and qualified interfaces, which
 /// are qualified with a protocol list like `NSString<NSCopyable, NSAmazing>`.

lib/AST/Type.cpp

: Type(ObjCObject, Canonical, Base->isDependentType(),
          Base->containsUnexpandedParameterPack()),
     BaseType(Base) 
 {
   ObjCObjectTypeBits.IsKindOf = isKindOf;
 
   ObjCObjectTypeBits.NumTypeArgs = typeArgs.size();
   assert(getTypeArgsAsWritten().size() == typeArgs.size() &&
          "bitfield overflow in type argument count");
-  ObjCObjectTypeBits.NumProtocols = protocols.size();
-  assert(getNumProtocols() == protocols.size() &&
-         "bitfield overflow in protocol count");
   if (!typeArgs.empty())
     memcpy(getTypeArgStorage(), typeArgs.data(),
            typeArgs.size() * sizeof(QualType));
-  if (!protocols.empty())
-    memcpy(getProtocolStorage(), protocols.data(),
-           protocols.size() * sizeof(ObjCProtocolDecl*));
 
   for (auto typeArg : typeArgs) {
     if (typeArg->isDependentType())
       setDependent();
     else if (typeArg->isInstantiationDependentType())
       setInstantiationDependent();
 
     if (typeArg->containsUnexpandedParameterPack())
       setContainsUnexpandedParameterPack();
   }
+  // Initialize the protocol qualifiers. The protocol storage is known
+  // after we set number of type arguments.
+  initialize(protocols);
 }
 
 bool ObjCObjectType::isSpecialized() const { 
   // If we have type arguments written here, the type is specialized.
   if (ObjCObjectTypeBits.NumTypeArgs > 0)
     return true;
 
   // Otherwise, check whether the base type is specialized.