Revamp to reflection.

Changes in brief:
1. Descriptor is now the entry point for all reflection.
2. IReflectedMessage has gone; there's now a Descriptor property in IMessage, which is explicitly implemented (due to the static property).
3. FieldAccessorTable has gone away
4. IFieldAccessor and OneofFieldAccessor still exist; we *could* put the functionality straight into FieldDescriptor and OneofDescriptor... I'm unsure about that.
5. There's a temporary property MessageDescriptor.FieldAccessorsByFieldNumber to make the test changes small - we probably want this to go away
6. Discovery for delegates is now via attributes applied to properties and the Clear method of a oneof

I'm happy with 1-3.
4 I'm unsure about - feedback welcome.
5 will go away
6 I'm unsure about, both in design and implementation. Should we have a ProtobufMessageAttribute too? Should we find all the relevant attributes in MessageDescriptor and pass them down, to avoid an O(N^2) scenario?

Generated code changes coming in the next commit.

13 files changed, 45 insertions, 99 deletions

diff --git a/src/google/protobuf/compiler/csharp/csharp_field_base.cc b/src/google/protobuf/compiler/csharp/csharp_field_base.cc
index 89d4eb18..d327e267 100644
--- a/src/google/protobuf/compiler/csharp/csharp_field_base.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_field_base.cc
@@ -74,6 +74,7 @@ void FieldGeneratorBase::SetCommonFieldVariables(
 
   (*variables)["property_name"] = property_name();
   (*variables)["type_name"] = type_name();
+  (*variables)["original_name"] = descriptor_->name();
   (*variables)["name"] = name();
   (*variables)["descriptor_name"] = descriptor_->name();
   (*variables)["default_value"] = default_value();
@@ -85,7 +86,6 @@ void FieldGeneratorBase::SetCommonFieldVariables(
   }
   (*variables)["capitalized_type_name"] = capitalized_type_name();
   (*variables)["number"] = number();
-  (*variables)["field_ordinal"] = field_ordinal();
   (*variables)["has_property_check"] =
     (*variables)["property_name"] + " != " + (*variables)["default_value"];
   (*variables)["other_has_property_check"] = "other." +
diff --git a/src/google/protobuf/compiler/csharp/csharp_helpers.h b/src/google/protobuf/compiler/csharp/csharp_helpers.h
index 653ff992..7737ffe2 100644
--- a/src/google/protobuf/compiler/csharp/csharp_helpers.h
+++ b/src/google/protobuf/compiler/csharp/csharp_helpers.h
@@ -77,6 +77,8 @@ std::string GetFullUmbrellaClassName(const FileDescriptor* descriptor);
 
 std::string GetQualifiedUmbrellaClassName(const FileDescriptor* descriptor);
 
+std::string GetClassName(const Descriptor* descriptor);
+
 std::string GetClassName(const EnumDescriptor* descriptor);
 
 std::string GetFieldName(const FieldDescriptor* descriptor);
@@ -119,10 +121,6 @@ inline bool IsDescriptorProto(const FileDescriptor* descriptor) {
   return descriptor->name() == "google/protobuf/descriptor_proto_file.proto";
 }
 
-inline bool IsMapEntry(const Descriptor* descriptor) {
-    return descriptor->options().map_entry();
-}
-
 inline bool IsWrapperType(const FieldDescriptor* descriptor) {
   return descriptor->type() == FieldDescriptor::TYPE_MESSAGE &&
       descriptor->message_type()->file()->name() == "google/protobuf/wrappers.proto";
diff --git a/src/google/protobuf/compiler/csharp/csharp_map_field.cc b/src/google/protobuf/compiler/csharp/csharp_map_field.cc
index cba24a59..bdbfd92b 100644
--- a/src/google/protobuf/compiler/csharp/csharp_map_field.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_map_field.cc
@@ -79,6 +79,7 @@ void MapFieldGenerator::GenerateMembers(io::Printer* printer) {
   AddDeprecatedFlag(printer);
   printer->Print(
     variables_,
+    "[pbr::ProtobufField($number$, \"$original_name$\")]\n"
     "$access_level$ pbc::MapField<$key_type_name$, $value_type_name$> $property_name$ {\n"
     "  get { return $name$_; }\n"
     "}\n");
diff --git a/src/google/protobuf/compiler/csharp/csharp_message.cc b/src/google/protobuf/compiler/csharp/csharp_message.cc
index 10cf3585..42fd5065 100644
--- a/src/google/protobuf/compiler/csharp/csharp_message.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_message.cc
@@ -96,88 +96,11 @@ const std::vector<const FieldDescriptor*>& MessageGenerator::fields_by_number()
   return fields_by_number_;
 }
 
-/// Get an identifier that uniquely identifies this type within the file.
-/// This is used to declare static variables related to this type at the
-/// outermost file scope.
-std::string GetUniqueFileScopeIdentifier(const Descriptor* descriptor) {
-  std::string result = descriptor->full_name();
-  std::replace(result.begin(), result.end(), '.', '_');
-  return "static_" + result;
-}
-
-void MessageGenerator::GenerateStaticVariables(io::Printer* printer) {
-  // Because descriptor.proto (Google.Protobuf.DescriptorProtos) is
-  // used in the construction of descriptors, we have a tricky bootstrapping
-  // problem.  To help control static initialization order, we make sure all
-  // descriptors and other static data that depends on them are members of
-  // the proto-descriptor class.  This way, they will be initialized in
-  // a deterministic order.
-
-  std::string identifier = GetUniqueFileScopeIdentifier(descriptor_);
-
-  // The descriptor for this type.
-  printer->Print(
-      "internal static pbr::FieldAccessorTable internal__$identifier$__FieldAccessorTable;\n",
-      "identifier", GetUniqueFileScopeIdentifier(descriptor_),
-      "full_class_name", full_class_name());
-
-  for (int i = 0; i < descriptor_->nested_type_count(); i++) {
-    // Don't generate accessor table fields for maps...
-    if (!IsMapEntryMessage(descriptor_->nested_type(i))) {
-      MessageGenerator messageGenerator(descriptor_->nested_type(i));
-      messageGenerator.GenerateStaticVariables(printer);
-    }
-  }
-}
-
-void MessageGenerator::GenerateStaticVariableInitializers(io::Printer* printer) {
-  map<string, string> vars;
-  vars["identifier"] = GetUniqueFileScopeIdentifier(descriptor_);
-  vars["full_class_name"] = full_class_name();
-
-  // Work out how to get to the message descriptor (which may be multiply nested) from the file
-  // descriptor.
-  string descriptor_chain;
-  const Descriptor* current_descriptor = descriptor_;
-  while (current_descriptor->containing_type()) {
-    descriptor_chain = ".NestedTypes[" + SimpleItoa(current_descriptor->index()) + "]" + descriptor_chain;
-    current_descriptor = current_descriptor->containing_type();
-  }
-  descriptor_chain = "descriptor.MessageTypes[" + SimpleItoa(current_descriptor->index()) + "]" + descriptor_chain;
-  vars["descriptor_chain"] = descriptor_chain;
-
-  printer->Print(
-    vars,
-    "internal__$identifier$__FieldAccessorTable = \n"
-    "    new pbr::FieldAccessorTable(typeof($full_class_name$), $descriptor_chain$,\n");
-  printer->Print("        new string[] { ");
-  for (int i = 0; i < descriptor_->field_count(); i++) {
-    printer->Print("\"$property_name$\", ",
-                   "property_name", GetPropertyName(descriptor_->field(i)));
-  }
-  printer->Print("}, new string[] { ");
-  for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
-    printer->Print("\"$oneof_name$\", ",
-                   "oneof_name",
-                   UnderscoresToCamelCase(descriptor_->oneof_decl(i)->name(), true));
-  }
-  printer->Print("});\n");
-
-  // Generate static member initializers for all non-map-entry nested types.
-  for (int i = 0; i < descriptor_->nested_type_count(); i++) {
-    if (!IsMapEntryMessage(descriptor_->nested_type(i))) {
-      MessageGenerator messageGenerator(descriptor_->nested_type(i));
-      messageGenerator.GenerateStaticVariableInitializers(printer);
-    }
-  }
-}
-
 void MessageGenerator::Generate(io::Printer* printer) {
   map<string, string> vars;
   vars["class_name"] = class_name();
   vars["access_level"] = class_access_level();
   vars["umbrella_class_name"] = GetFullUmbrellaClassName(descriptor_->file());
-  vars["identifier"] = GetUniqueFileScopeIdentifier(descriptor_);
 
   printer->Print(
     "[global::System.Diagnostics.DebuggerNonUserCodeAttribute()]\n");
@@ -221,8 +144,8 @@ void MessageGenerator::Generate(io::Printer* printer) {
     "  get { return $descriptor_accessor$; }\n"
     "}\n"
     "\n"
-    "pbr::FieldAccessorTable pb::IReflectedMessage.Fields {\n"
-    "  get { return $umbrella_class_name$.internal__$identifier$__FieldAccessorTable; }\n"
+    "pbr::MessageDescriptor pb::IMessage.Descriptor {\n"
+    "  get { return Descriptor; }\n"
     "}\n"
     "\n"
     "private bool _frozen = false;\n"
@@ -258,6 +181,7 @@ void MessageGenerator::Generate(io::Printer* printer) {
   for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
     vars["name"] = UnderscoresToCamelCase(descriptor_->oneof_decl(i)->name(), false);
     vars["property_name"] = UnderscoresToCamelCase(descriptor_->oneof_decl(i)->name(), true);
+    vars["original_name"] = descriptor_->oneof_decl(i)->name();
     printer->Print(
       vars,
       "private object $name$_;\n"
@@ -275,9 +199,11 @@ void MessageGenerator::Generate(io::Printer* printer) {
     printer->Print(
       vars,
       "private $property_name$OneofCase $name$Case_ = $property_name$OneofCase.None;\n"
+      "[pbr::ProtobufOneof(\"$original_name$\")]\n"
       "public $property_name$OneofCase $property_name$Case {\n"
       "  get { return $name$Case_; }\n"
       "}\n\n"
+      "[pbr::ProtobufOneof(\"$original_name$\")]\n"
       "public void Clear$property_name$() {\n"
       "  pb::Freezable.CheckMutable(this);\n"
       "  $name$Case_ = $property_name$OneofCase.None;\n"
diff --git a/src/google/protobuf/compiler/csharp/csharp_message.h b/src/google/protobuf/compiler/csharp/csharp_message.h
index fbe8a3be..f0c49ac9 100644
--- a/src/google/protobuf/compiler/csharp/csharp_message.h
+++ b/src/google/protobuf/compiler/csharp/csharp_message.h
@@ -53,8 +53,6 @@ class MessageGenerator : public SourceGeneratorBase {
   void GenerateCloningCode(io::Printer* printer);
   void GenerateFreezingCode(io::Printer* printer);
   void GenerateFrameworkMethods(io::Printer* printer);
-  void GenerateStaticVariables(io::Printer* printer);
-  void GenerateStaticVariableInitializers(io::Printer* printer);
   void Generate(io::Printer* printer);
 
  private:
diff --git a/src/google/protobuf/compiler/csharp/csharp_message_field.cc b/src/google/protobuf/compiler/csharp/csharp_message_field.cc
index d2c3a88b..c2b6ff76 100644
--- a/src/google/protobuf/compiler/csharp/csharp_message_field.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_message_field.cc
@@ -64,6 +64,7 @@ void MessageFieldGenerator::GenerateMembers(io::Printer* printer) {
   AddDeprecatedFlag(printer);
   printer->Print(
     variables_,
+    "[pbr::ProtobufField($number$, \"$original_name$\")]\n"
     "$access_level$ $type_name$ $property_name$ {\n"
     "  get { return $name$_; }\n"
     "  set {\n"
@@ -158,6 +159,7 @@ void MessageOneofFieldGenerator::GenerateMembers(io::Printer* printer) {
   AddDeprecatedFlag(printer);
   printer->Print(
     variables_,
+    "[pbr::ProtobufField($number$, \"$original_name$\")]\n"
     "$access_level$ $type_name$ $property_name$ {\n"
     "  get { return $has_property_check$ ? ($type_name$) $oneof_name$_ : null; }\n"
     "  set {\n"
diff --git a/src/google/protobuf/compiler/csharp/csharp_primitive_field.cc b/src/google/protobuf/compiler/csharp/csharp_primitive_field.cc
index 4454ef02..2c9338bd 100644
--- a/src/google/protobuf/compiler/csharp/csharp_primitive_field.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_primitive_field.cc
@@ -71,6 +71,7 @@ void PrimitiveFieldGenerator::GenerateMembers(io::Printer* printer) {
   AddDeprecatedFlag(printer);
   printer->Print(
     variables_,
+    "[pbr::ProtobufField($number$, \"$original_name$\")]\n"
     "$access_level$ $type_name$ $property_name$ {\n"
     "  get { return $name$_; }\n"
     "  set {\n"
@@ -174,6 +175,7 @@ void PrimitiveOneofFieldGenerator::GenerateMembers(io::Printer* printer) {
   AddDeprecatedFlag(printer);
   printer->Print(
     variables_,
+    "[pbr::ProtobufField($number$, \"$original_name$\")]\n"
     "$access_level$ $type_name$ $property_name$ {\n"
     "  get { return $has_property_check$ ? ($type_name$) $oneof_name$_ : $default_value$; }\n"
     "  set {\n"
diff --git a/src/google/protobuf/compiler/csharp/csharp_repeated_enum_field.cc b/src/google/protobuf/compiler/csharp/csharp_repeated_enum_field.cc
index d5fc6d98..60d06154 100644
--- a/src/google/protobuf/compiler/csharp/csharp_repeated_enum_field.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_repeated_enum_field.cc
@@ -59,12 +59,13 @@ void RepeatedEnumFieldGenerator::GenerateMembers(io::Printer* printer) {
   printer->Print(
     variables_,
     "private static readonly pb::FieldCodec<$type_name$> _repeated_$name$_codec\n"
-    "    = pb::FieldCodec.ForEnum($tag$, x => (int) x, x => ($type_name$) x);");
+    "    = pb::FieldCodec.ForEnum($tag$, x => (int) x, x => ($type_name$) x);\n");
   printer->Print(variables_,
     "private readonly pbc::RepeatedField<$type_name$> $name$_ = new pbc::RepeatedField<$type_name$>();\n");
   AddDeprecatedFlag(printer);
   printer->Print(
     variables_,
+    "[pbr::ProtobufField($number$, \"$original_name$\")]\n"
     "$access_level$ pbc::RepeatedField<$type_name$> $property_name$ {\n"
     "  get { return $name$_; }\n"
     "}\n");
diff --git a/src/google/protobuf/compiler/csharp/csharp_repeated_message_field.cc b/src/google/protobuf/compiler/csharp/csharp_repeated_message_field.cc
index d939fc79..921798b0 100644
--- a/src/google/protobuf/compiler/csharp/csharp_repeated_message_field.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_repeated_message_field.cc
@@ -78,6 +78,7 @@ void RepeatedMessageFieldGenerator::GenerateMembers(io::Printer* printer) {
   AddDeprecatedFlag(printer);
   printer->Print(
     variables_,
+    "[pbr::ProtobufField($number$, \"$original_name$\")]\n"
     "$access_level$ pbc::RepeatedField<$type_name$> $property_name$ {\n"
     "  get { return $name$_; }\n"
     "}\n");
diff --git a/src/google/protobuf/compiler/csharp/csharp_repeated_primitive_field.cc b/src/google/protobuf/compiler/csharp/csharp_repeated_primitive_field.cc
index 5b5d9b3d..bcfb9936 100644
--- a/src/google/protobuf/compiler/csharp/csharp_repeated_primitive_field.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_repeated_primitive_field.cc
@@ -65,6 +65,7 @@ void RepeatedPrimitiveFieldGenerator::GenerateMembers(io::Printer* printer) {
   AddDeprecatedFlag(printer);
   printer->Print(
     variables_,
+    "[pbr::ProtobufField($number$, \"$original_name$\")]\n"
     "$access_level$ pbc::RepeatedField<$type_name$> $property_name$ {\n"
     "  get { return $name$_; }\n"
     "}\n");
diff --git a/src/google/protobuf/compiler/csharp/csharp_umbrella_class.cc b/src/google/protobuf/compiler/csharp/csharp_umbrella_class.cc
index 57271d17..3f39250e 100644
--- a/src/google/protobuf/compiler/csharp/csharp_umbrella_class.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_umbrella_class.cc
@@ -63,12 +63,6 @@ UmbrellaClassGenerator::~UmbrellaClassGenerator() {
 void UmbrellaClassGenerator::Generate(io::Printer* printer) {
   WriteIntroduction(printer);
 
-  printer->Print("#region Static variables\n");
-  for (int i = 0; i < file_->message_type_count(); i++) {
-    MessageGenerator messageGenerator(file_->message_type(i));
-    messageGenerator.GenerateStaticVariables(printer);
-  }
-  printer->Print("#endregion\n");
   WriteDescriptor(printer);
   // Close the class declaration.
   printer->Outdent();
@@ -183,24 +177,43 @@ void UmbrellaClassGenerator::WriteDescriptor(io::Printer* printer) {
   // Invoke InternalBuildGeneratedFileFrom() to build the file.
   printer->Print(
       "descriptor = pbr::FileDescriptor.InternalBuildGeneratedFileFrom(descriptorData,\n");
-  printer->Print("    new pbr::FileDescriptor[] {\n");
+  printer->Print("    new pbr::FileDescriptor[] { ");
   for (int i = 0; i < file_->dependency_count(); i++) {
     printer->Print(
-      "    $full_umbrella_class_name$.Descriptor, \n",
+      "$full_umbrella_class_name$.Descriptor, ",
       "full_umbrella_class_name",
       GetFullUmbrellaClassName(file_->dependency(i)));
   }
-  printer->Print("    });\n");
-  // Then invoke any other static variable initializers, e.g. field accessors.
+  // Specify all the generated types (messages and enums), recursively, as an array. 
+  printer->Print("},\n"
+    "    new global::System.Type[] { ");
   for (int i = 0; i < file_->message_type_count(); i++) {
-      MessageGenerator messageGenerator(file_->message_type(i));
-      messageGenerator.GenerateStaticVariableInitializers(printer);
+    WriteTypeLiterals(file_->message_type(i), printer);
   }
+  for (int i = 0; i < file_->enum_type_count(); i++) {
+    printer->Print("typeof($type_name$), ", "type_name", GetClassName(file_->enum_type(i)));
+  }
+  printer->Print("});\n");
+
   printer->Outdent();
   printer->Print("}\n");
   printer->Print("#endregion\n\n");
 }
 
+void UmbrellaClassGenerator::WriteTypeLiterals(const Descriptor* descriptor, io::Printer* printer) {
+    if (IsMapEntryMessage(descriptor)) {
+        printer->Print("null, ");
+        return;
+    }
+    printer->Print("typeof($type_name$), ", "type_name", GetClassName(descriptor));
+    for (int i = 0; i < descriptor->nested_type_count(); i++) {
+        WriteTypeLiterals(descriptor->nested_type(i), printer);
+    }
+    for (int i = 0; i < descriptor->enum_type_count(); i++) {
+        printer->Print("typeof($type_name$), ", "type_name", GetClassName(descriptor->enum_type(i)));
+    }
+}
+
 }  // namespace csharp
 }  // namespace compiler
 }  // namespace protobuf
diff --git a/src/google/protobuf/compiler/csharp/csharp_umbrella_class.h b/src/google/protobuf/compiler/csharp/csharp_umbrella_class.h
index f7533d2d..db1092a9 100644
--- a/src/google/protobuf/compiler/csharp/csharp_umbrella_class.h
+++ b/src/google/protobuf/compiler/csharp/csharp_umbrella_class.h
@@ -57,6 +57,7 @@ class UmbrellaClassGenerator : public SourceGeneratorBase {
 
   void WriteIntroduction(io::Printer* printer);
   void WriteDescriptor(io::Printer* printer);
+  void WriteTypeLiterals(const Descriptor* descriptor, io::Printer* printer);
 
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(UmbrellaClassGenerator);
 };
diff --git a/src/google/protobuf/compiler/csharp/csharp_wrapper_field.cc b/src/google/protobuf/compiler/csharp/csharp_wrapper_field.cc
index 75ef5e50..d6cd0a10 100644
--- a/src/google/protobuf/compiler/csharp/csharp_wrapper_field.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_wrapper_field.cc
@@ -73,6 +73,7 @@ void WrapperFieldGenerator::GenerateMembers(io::Printer* printer) {
   AddDeprecatedFlag(printer);
   printer->Print(
     variables_,
+    "[pbr::ProtobufField($number$, \"$original_name$\")]\n"
     "$access_level$ $type_name$ $property_name$ {\n"
     "  get { return $name$_; }\n"
     "  set {\n"
@@ -169,6 +170,7 @@ void WrapperOneofFieldGenerator::GenerateMembers(io::Printer* printer) {
   AddDeprecatedFlag(printer);
   printer->Print(
     variables_,
+    "[pbr::ProtobufField($number$, \"$original_name$\")]\n"
     "$access_level$ $type_name$ $property_name$ {\n"
     "  get { return $has_property_check$ ? ($type_name$) $oneof_name$_ : ($type_name$) null; }\n"
     "  set {\n"