[Runtime] Remove demangleObjCTypeName and use the old demangler instead.

Archiving expects to be able to instantiate generic classes by name. This previously worked if you had instantiated the specialization in question, because the ObjC runtime would be able to look it up. Now, if the name hasn't been created, Swift has to look it up. demangleObjCTypeName doesn't do generics, so this failed.

rdar://problem/57674583

Author: mikeash

include/swift/Demangling/Demangler.h

@@ -563,7 +563,6 @@ class Demangler : public NodeFactory {
   NodePointer demangleGenericType();
   NodePointer demangleValueWitness();
 
-  NodePointer demangleObjCTypeName();
   NodePointer demangleTypeMangling();
   NodePointer demangleSymbolicReference(unsigned char rawKind,
                                         const void *at);

lib/Demangling/Demangler.cpp

@@ -529,7 +529,7 @@ NodePointer Demangler::demangleSymbol(StringRef MangledName,
   // Demangle old-style class and protocol names, which are still used in the
   // ObjC metadata.
   if (nextIf("_Tt"))
-    return demangleObjCTypeName();
+    return demangleOldSymbolAsNode(Text, *this);
 
   unsigned PrefixLength = getManglingPrefixLength(MangledName);
   if (PrefixLength == 0)
@@ -3193,45 +3193,3 @@ NodePointer Demangler::demangleValueWitness() {
   addChild(VW, createNode(Node::Kind::Index, unsigned(Kind)));
   return addChild(VW, popNode(Node::Kind::Type));
 }
-
-NodePointer Demangler::demangleObjCTypeName() {
-  NodePointer Ty = createNode(Node::Kind::Type);
-  NodePointer Global = addChild(createNode(Node::Kind::Global),
-                         addChild(createNode(Node::Kind::TypeMangling), Ty));
-  NodePointer Nominal = nullptr;
-  bool isProto = false;
-  if (nextIf('C')) {
-    Nominal = createNode(Node::Kind::Class);
-    addChild(Ty, Nominal);
-  } else if (nextIf('P')) {
-    isProto = true;
-    Nominal = createNode(Node::Kind::Protocol);
-    addChild(Ty, addChild(createNode(Node::Kind::ProtocolList),
-                    addChild(createNode(Node::Kind::TypeList),
-                      addChild(createNode(Node::Kind::Type), Nominal))));
-  } else {
-    return nullptr;
-  }
-
-  if (nextIf('s')) {
-    Nominal->addChild(createNode(Node::Kind::Module, "Swift"), *this);
-  } else {
-    NodePointer Module = demangleIdentifier();
-    if (!Module)
-      return nullptr;
-    Nominal->addChild(changeKind(Module, Node::Kind::Module), *this);
-  }
-
-  NodePointer Ident = demangleIdentifier();
-  if (!Ident)
-    return nullptr;
-  Nominal->addChild(Ident, *this);
-
-  if (isProto && !nextIf('_'))
-    return nullptr;
-
-  if (Pos < Text.size())
-    return nullptr;
-
-  return Global;
-}