Change the backing base name type of DeclName to DeclBaseName

The new DeclBaseName type will later be able to hold either normal
identifiers (as they exist now) or special names that don't have an
identifier (like subscripts)

Author: ahoppen

include/swift/AST/Identifier.h

@@ -192,7 +192,7 @@ namespace llvm {
   class PointerLikeTypeTraits<swift::Identifier> {
   public:
     static inline void *getAsVoidPointer(swift::Identifier I) {
-      return (void*)I.get();
+      return const_cast<void *>(I.getAsOpaquePointer());
     }
     static inline swift::Identifier getFromVoidPointer(void *P) {
       return swift::Identifier::getFromOpaquePointer(P);
@@ -203,7 +203,54 @@ namespace llvm {
 } // end namespace llvm
 
 namespace swift {
-  
+
+/// Wrapper that may either be an Identifier or a special name
+/// (e.g. for subscripts)
+class DeclBaseName {
+  Identifier Ident;
+
+public:
+  DeclBaseName(Identifier I) : Ident(I) {}
+
+  bool isSpecial() const { return false; }
+
+  /// Return the identifier backing the name. Assumes that the name is not
+  /// special.
+  Identifier getIdentifier() const {
+    assert(!isSpecial() && "Cannot retrieve identifier from special names");
+    return Ident;
+  }
+
+  bool empty() const { return !isSpecial() && getIdentifier().empty(); }
+
+  const void *getAsOpaquePointer() const { return Ident.get(); }
+
+  static DeclBaseName getFromOpaquePointer(void *P) {
+    return Identifier::getFromOpaquePointer(P);
+  }
+};
+
+} // end namespace swift
+
+namespace llvm {
+
+// A DeclBaseName is "pointer like".
+template <typename T> class PointerLikeTypeTraits;
+template <> class PointerLikeTypeTraits<swift::DeclBaseName> {
+public:
+  static inline void *getAsVoidPointer(swift::DeclBaseName D) {
+    return const_cast<void *>(D.getAsOpaquePointer());
+  }
+  static inline swift::DeclBaseName getFromVoidPointer(void *P) {
+    return swift::DeclBaseName::getFromOpaquePointer(P);
+  }
+  enum { NumLowBitsAvailable = PointerLikeTypeTraits<swift::Identifier>::NumLowBitsAvailable };
+};
+
+} // end namespace llvm
+
+namespace swift {
+
 /// A declaration name, which may comprise one or more identifier pieces.
 class DeclName {
   friend class ASTContext;
@@ -214,12 +261,11 @@ class DeclName {
     friend TrailingObjects;
     friend class DeclName;
 
-    Identifier BaseName;
+    DeclBaseName BaseName;
     size_t NumArgs;
-    
-    explicit CompoundDeclName(Identifier BaseName, size_t NumArgs)
-      : BaseName(BaseName), NumArgs(NumArgs)
-    {
+
+    explicit CompoundDeclName(DeclBaseName BaseName, size_t NumArgs)
+        : BaseName(BaseName), NumArgs(NumArgs) {
       assert(NumArgs > 0 && "Should use IdentifierAndCompound");
     }
 
@@ -231,56 +277,61 @@ class DeclName {
     }
 
     /// Uniquing for the ASTContext.
-    static void Profile(llvm::FoldingSetNodeID &id,
-                        Identifier baseName,
+    static void Profile(llvm::FoldingSetNodeID &id, DeclBaseName baseName,
                         ArrayRef<Identifier> argumentNames);
-    
+
     void Profile(llvm::FoldingSetNodeID &id) {
       Profile(id, BaseName, getArgumentNames());
     }
   };
 
   // A single stored identifier, along with a bit stating whether it is the
   // base name for a zero-argument compound name.
-  typedef llvm::PointerIntPair<Identifier, 1, bool> IdentifierAndCompound;
+  typedef llvm::PointerIntPair<DeclBaseName, 1, bool> BaseNameAndCompound;
 
   // Either a single identifier piece stored inline (with a bit to say whether
   // it is simple or compound), or a reference to a compound declaration name.
-  llvm::PointerUnion<IdentifierAndCompound, CompoundDeclName*> SimpleOrCompound;
-  
+  llvm::PointerUnion<BaseNameAndCompound, CompoundDeclName *> SimpleOrCompound;
+
   DeclName(void *Opaque)
     : SimpleOrCompound(decltype(SimpleOrCompound)::getFromOpaqueValue(Opaque))
   {}
 
-  void initialize(ASTContext &C, Identifier baseName,
+  void initialize(ASTContext &C, DeclBaseName baseName,
                   ArrayRef<Identifier> argumentNames);
-  
+
 public:
   /// Build a null name.
-  DeclName() : SimpleOrCompound(IdentifierAndCompound()) {}
-  
+  DeclName() : SimpleOrCompound(BaseNameAndCompound()) {}
+
   /// Build a simple value name with one component.
+  /*implicit*/ DeclName(DeclBaseName simpleName)
+      : SimpleOrCompound(BaseNameAndCompound(simpleName, false)) {}
+
   /*implicit*/ DeclName(Identifier simpleName)
-    : SimpleOrCompound(IdentifierAndCompound(simpleName, false)) {}
-  
+      : DeclName(DeclBaseName(simpleName)) {}
+
   /// Build a compound value name given a base name and a set of argument names.
-  DeclName(ASTContext &C, Identifier baseName,
+  DeclName(ASTContext &C, DeclBaseName baseName,
            ArrayRef<Identifier> argumentNames) {
     initialize(C, baseName, argumentNames);
   }
 
   /// Build a compound value name given a base name and a set of argument names
   /// extracted from a parameter list.
-  DeclName(ASTContext &C, Identifier baseName, ParameterList *paramList);
-  
+  DeclName(ASTContext &C, DeclBaseName baseName, ParameterList *paramList);
+
   /// Retrieve the 'base' name, i.e., the name that follows the introducer,
   /// such as the 'foo' in 'func foo(x:Int, y:Int)' or the 'bar' in
   /// 'var bar: Int'.
+  // TODO: Return DeclBaseName (remove two calls to getIdentifier)
   Identifier getBaseName() const {
     if (auto compound = SimpleOrCompound.dyn_cast<CompoundDeclName*>())
-      return compound->BaseName;
-    
-    return SimpleOrCompound.get<IdentifierAndCompound>().getPointer();
+      return compound->BaseName.getIdentifier();
+
+    return SimpleOrCompound.get<BaseNameAndCompound>()
+        .getPointer()
+        .getIdentifier();
   }
 
   /// Retrieve the names of the arguments, if there are any.
@@ -294,23 +345,23 @@ class DeclName {
   explicit operator bool() const {
     if (SimpleOrCompound.dyn_cast<CompoundDeclName*>())
       return true;
-    return !SimpleOrCompound.get<IdentifierAndCompound>().getPointer().empty();
+    return !SimpleOrCompound.get<BaseNameAndCompound>().getPointer().empty();
   }
 
   /// True if this is a simple one-component name.
   bool isSimpleName() const {
     if (SimpleOrCompound.dyn_cast<CompoundDeclName*>())
       return false;
 
-    return !SimpleOrCompound.get<IdentifierAndCompound>().getInt();
+    return !SimpleOrCompound.get<BaseNameAndCompound>().getInt();
   }
 
   /// True if this is a compound name.
   bool isCompoundName() const {
     if (SimpleOrCompound.dyn_cast<CompoundDeclName*>())
       return true;
 
-    return SimpleOrCompound.get<IdentifierAndCompound>().getInt();
+    return SimpleOrCompound.get<BaseNameAndCompound>().getInt();
   }
 
   /// True if this name is a simple one-component name identical to the

lib/AST/ASTContext.cpp

@@ -3527,18 +3527,18 @@ GenericEnvironment *GenericEnvironment::getIncomplete(
 }
 
 void DeclName::CompoundDeclName::Profile(llvm::FoldingSetNodeID &id,
-                                         Identifier baseName,
+                                         DeclBaseName baseName,
                                          ArrayRef<Identifier> argumentNames) {
-  id.AddPointer(baseName.get());
+  id.AddPointer(baseName.getAsOpaquePointer());
   id.AddInteger(argumentNames.size());
   for (auto arg : argumentNames)
     id.AddPointer(arg.get());
 }
 
-void DeclName::initialize(ASTContext &C, Identifier baseName,
+void DeclName::initialize(ASTContext &C, DeclBaseName baseName,
                           ArrayRef<Identifier> argumentNames) {
   if (argumentNames.size() == 0) {
-    SimpleOrCompound = IdentifierAndCompound(baseName, true);
+    SimpleOrCompound = BaseNameAndCompound(baseName, true);
     return;
   }
 
@@ -3564,7 +3564,7 @@ void DeclName::initialize(ASTContext &C, Identifier baseName,
 
 /// Build a compound value name given a base name and a set of argument names
 /// extracted from a parameter list.
-DeclName::DeclName(ASTContext &C, Identifier baseName,
+DeclName::DeclName(ASTContext &C, DeclBaseName baseName,
                    ParameterList *paramList) {
   SmallVector<Identifier, 4> names;