Down integrate from Google internal.

20 files changed, 331 insertions, 479 deletions

diff --git a/src/google/protobuf/compiler/java/java_doc_comment.cc b/src/google/protobuf/compiler/java/java_doc_comment.cc
index 663f0c97..0b5caba4 100644
--- a/src/google/protobuf/compiler/java/java_doc_comment.cc
+++ b/src/google/protobuf/compiler/java/java_doc_comment.cc
@@ -120,9 +120,7 @@ static void WriteDocCommentBodyForLocation(
       lines.pop_back();
     }
 
-    printer->Print(
-        " *\n"
-        " * <pre>\n");
+    printer->Print(" * <pre>\n");
     for (int i = 0; i < lines.size(); i++) {
       // Most lines should start with a space.  Watch out for lines that start
       // with a /, since putting that right after the leading asterisk will
@@ -133,7 +131,9 @@ static void WriteDocCommentBodyForLocation(
         printer->Print(" *$line$\n", "line", lines[i]);
       }
     }
-    printer->Print(" * </pre>\n");
+    printer->Print(
+        " * </pre>\n"
+        " *\n");
   }
 }
 
@@ -163,12 +163,12 @@ static string FirstLineOf(const string& value) {
 }
 
 void WriteMessageDocComment(io::Printer* printer, const Descriptor* message) {
+  printer->Print("/**\n");
+  WriteDocCommentBody(printer, message);
   printer->Print(
-    "/**\n"
-    " * Protobuf type {@code $fullname$}\n",
+    " * Protobuf type {@code $fullname$}\n"
+    " */\n",
     "fullname", EscapeJavadoc(message->full_name()));
-  WriteDocCommentBody(printer, message);
-  printer->Print(" */\n");
 }
 
 void WriteFieldDocComment(io::Printer* printer, const FieldDescriptor* field) {
@@ -176,55 +176,55 @@ void WriteFieldDocComment(io::Printer* printer, const FieldDescriptor* field) {
   // etc., but in practice everyone already knows the difference between these
   // so it's redundant information.
 
-  // We use the field declaration as the first line of the comment, e.g.:
+  // We start the comment with the main body based on the comments from the
+  // .proto file (if present). We then end with the field declaration, e.g.:
   //   optional string foo = 5;
-  // This communicates a lot of information about the field in a small space.
   // If the field is a group, the debug string might end with {.
+  printer->Print("/**\n");
+  WriteDocCommentBody(printer, field);
   printer->Print(
-    "/**\n"
     " * <code>$def$</code>\n",
     "def", EscapeJavadoc(FirstLineOf(field->DebugString())));
-  WriteDocCommentBody(printer, field);
   printer->Print(" */\n");
 }
 
 void WriteEnumDocComment(io::Printer* printer, const EnumDescriptor* enum_) {
+  printer->Print("/**\n");
+  WriteDocCommentBody(printer, enum_);
   printer->Print(
-    "/**\n"
-    " * Protobuf enum {@code $fullname$}\n",
+    " * Protobuf enum {@code $fullname$}\n"
+    " */\n",
     "fullname", EscapeJavadoc(enum_->full_name()));
-  WriteDocCommentBody(printer, enum_);
-  printer->Print(" */\n");
 }
 
 void WriteEnumValueDocComment(io::Printer* printer,
                               const EnumValueDescriptor* value) {
+  printer->Print("/**\n");
+  WriteDocCommentBody(printer, value);
   printer->Print(
-    "/**\n"
-    " * <code>$def$</code>\n",
+    " * <code>$def$</code>\n"
+    " */\n",
     "def", EscapeJavadoc(FirstLineOf(value->DebugString())));
-  WriteDocCommentBody(printer, value);
-  printer->Print(" */\n");
 }
 
 void WriteServiceDocComment(io::Printer* printer,
                             const ServiceDescriptor* service) {
+  printer->Print("/**\n");
+  WriteDocCommentBody(printer, service);
   printer->Print(
-    "/**\n"
-    " * Protobuf service {@code $fullname$}\n",
+    " * Protobuf service {@code $fullname$}\n"
+    " */\n",
     "fullname", EscapeJavadoc(service->full_name()));
-  WriteDocCommentBody(printer, service);
-  printer->Print(" */\n");
 }
 
 void WriteMethodDocComment(io::Printer* printer,
                            const MethodDescriptor* method) {
+  printer->Print("/**\n");
+  WriteDocCommentBody(printer, method);
   printer->Print(
-    "/**\n"
-    " * <code>$def$</code>\n",
+    " * <code>$def$</code>\n"
+    " */\n",
     "def", EscapeJavadoc(FirstLineOf(method->DebugString())));
-  WriteDocCommentBody(printer, method);
-  printer->Print(" */\n");
 }
 
 }  // namespace java
diff --git a/src/google/protobuf/compiler/java/java_enum.cc b/src/google/protobuf/compiler/java/java_enum.cc
index 9eea873a..947b80e4 100644
--- a/src/google/protobuf/compiler/java/java_enum.cc
+++ b/src/google/protobuf/compiler/java/java_enum.cc
@@ -92,6 +92,16 @@ void EnumGenerator::Generate(io::Printer* printer) {
     "classname", descriptor_->name());
   printer->Indent();
 
+  bool ordinal_is_index = true;
+  string index_text = "ordinal()";
+  for (int i = 0; i < canonical_values_.size(); i++) {
+    if (canonical_values_[i]->index() != i) {
+      ordinal_is_index = false;
+      index_text = "index";
+      break;
+    }
+  }
+
   for (int i = 0; i < canonical_values_.size(); i++) {
     map<string, string> vars;
     vars["name"] = canonical_values_[i]->name();
@@ -101,12 +111,21 @@ void EnumGenerator::Generate(io::Printer* printer) {
     if (canonical_values_[i]->options().deprecated()) {
       printer->Print("@java.lang.Deprecated\n");
     }
-    printer->Print(vars,
-      "$name$($index$, $number$),\n");
+    if (ordinal_is_index) {
+      printer->Print(vars,
+        "$name$($number$),\n");
+    } else {
+      printer->Print(vars,
+        "$name$($index$, $number$),\n");
+    }
   }
 
   if (SupportUnknownEnumValue(descriptor_->file())) {
-    printer->Print("UNRECOGNIZED(-1, -1),\n");
+    if (ordinal_is_index) {
+      printer->Print("UNRECOGNIZED(-1),\n");
+    } else {
+      printer->Print("UNRECOGNIZED(-1, -1),\n");
+    }
   }
 
   printer->Print(
@@ -141,11 +160,19 @@ void EnumGenerator::Generate(io::Printer* printer) {
     "\n"
     "public final int getNumber() {\n");
   if (SupportUnknownEnumValue(descriptor_->file())) {
-    printer->Print(
-      "  if (index == -1) {\n"
-      "    throw new java.lang.IllegalArgumentException(\n"
-      "        \"Can't get the number of an unknown enum value.\");\n"
-      "  }\n");
+    if (ordinal_is_index) {
+      printer->Print(
+        "  if (this == UNRECOGNIZED) {\n"
+        "    throw new java.lang.IllegalArgumentException(\n"
+        "        \"Can't get the number of an unknown enum value.\");\n"
+        "  }\n");
+    } else {
+      printer->Print(
+        "  if (index == -1) {\n"
+        "    throw new java.lang.IllegalArgumentException(\n"
+        "        \"Can't get the number of an unknown enum value.\");\n"
+        "  }\n");
+    }
   }
   printer->Print(
     "  return value;\n"
@@ -200,14 +227,15 @@ void EnumGenerator::Generate(io::Printer* printer) {
     printer->Print(
       "public final com.google.protobuf.Descriptors.EnumValueDescriptor\n"
       "    getValueDescriptor() {\n"
-      "  return getDescriptor().getValues().get(index);\n"
+      "  return getDescriptor().getValues().get($index_text$);\n"
       "}\n"
       "public final com.google.protobuf.Descriptors.EnumDescriptor\n"
       "    getDescriptorForType() {\n"
       "  return getDescriptor();\n"
       "}\n"
       "public static final com.google.protobuf.Descriptors.EnumDescriptor\n"
-      "    getDescriptor() {\n");
+      "    getDescriptor() {\n",
+      "index_text", index_text);
 
     // TODO(kenton):  Cache statically?  Note that we can't access descriptors
     //   at module init time because it wouldn't work with descriptor.proto, but
@@ -313,16 +341,27 @@ void EnumGenerator::Generate(io::Printer* printer) {
       "}\n"
       "\n");
 
-    printer->Print("private final int index;\n");
+    if (!ordinal_is_index) {
+      printer->Print("private final int index;\n");
+    }
   }
 
   // -----------------------------------------------------------------
 
   printer->Print(
-    "private final int value;\n\n"
-    "private $classname$(int index, int value) {\n",
-    "classname", descriptor_->name());
-  if (HasDescriptorMethods(descriptor_, context_->EnforceLite())) {
+    "private final int value;\n\n");
+
+  if (ordinal_is_index) {
+    printer->Print(
+      "private $classname$(int value) {\n",
+      "classname", descriptor_->name());
+  } else {
+    printer->Print(
+      "private $classname$(int index, int value) {\n",
+      "classname", descriptor_->name());
+  }
+  if (HasDescriptorMethods(descriptor_, context_->EnforceLite()) &&
+      !ordinal_is_index) {
     printer->Print("  this.index = index;\n");
   }
   printer->Print(
diff --git a/src/google/protobuf/compiler/java/java_enum_field_lite.cc b/src/google/protobuf/compiler/java/java_enum_field_lite.cc
index 5b98637b..908d6db4 100644
--- a/src/google/protobuf/compiler/java/java_enum_field_lite.cc
+++ b/src/google/protobuf/compiler/java/java_enum_field_lite.cc
@@ -262,17 +262,15 @@ GenerateInitializationCode(io::Printer* printer) const {
 }
 
 void ImmutableEnumFieldLiteGenerator::
-GenerateMergingCode(io::Printer* printer) const {
+GenerateVisitCode(io::Printer* printer) const {
   if (SupportFieldPresence(descriptor_->file())) {
     printer->Print(variables_,
-      "if (other.has$capitalized_name$()) {\n"
-      "  set$capitalized_name$(other.get$capitalized_name$());\n"
-      "}\n");
+      "$name$_ = visitor.visitInt(has$capitalized_name$(), $name$_,\n"
+      "    other.has$capitalized_name$(), other.$name$_);\n");
   } else if (SupportUnknownEnumValue(descriptor_->file())) {
     printer->Print(variables_,
-      "if (other.$name$_ != $default_number$) {\n"
-      "  set$capitalized_name$Value(other.get$capitalized_name$Value());\n"
-      "}\n");
+      "$name$_ = visitor.visitInt($name$_ != $default_number$, $name$_,"
+      "    other.$name$_ != $default_number$, other.$name$_);\n");
   } else {
     GOOGLE_LOG(FATAL) << "Can't reach here.";
   }
@@ -466,14 +464,10 @@ GenerateBuilderMembers(io::Printer* printer) const {
 }
 
 void ImmutableEnumOneofFieldLiteGenerator::
-GenerateMergingCode(io::Printer* printer) const {
-  if (SupportUnknownEnumValue(descriptor_->file())) {
-    printer->Print(variables_,
-      "set$capitalized_name$Value(other.get$capitalized_name$Value());\n");
-  } else {
-    printer->Print(variables_,
-      "set$capitalized_name$(other.get$capitalized_name$());\n");
-  }
+GenerateVisitCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "$oneof_name$_ = visitor.visitOneofInt(\n"
+    "   $has_oneof_case_message$, $oneof_name$_, other.$oneof_name$_);\n");
 }
 
 void ImmutableEnumOneofFieldLiteGenerator::
@@ -645,7 +639,8 @@ GenerateMembers(io::Printer* printer) const {
   printer->Print(variables_,
     "private void ensure$capitalized_name$IsMutable() {\n"
     "  if (!$is_mutable$) {\n"
-    "    $name$_ = newIntList($name$_);\n"
+    "    $name$_ =\n"
+    "        com.google.protobuf.GeneratedMessageLite.mutableCopy($name$_);\n"
     "  }\n"
     "}\n");
   WriteFieldDocComment(printer, descriptor_);
@@ -805,21 +800,9 @@ GenerateInitializationCode(io::Printer* printer) const {
 }
 
 void RepeatedImmutableEnumFieldLiteGenerator::
-GenerateMergingCode(io::Printer* printer) const {
-  // The code below does two optimizations:
-  //   1. If the other list is empty, there's nothing to do. This ensures we
-  //      don't allocate a new array if we already have an immutable one.
-  //   2. If the other list is non-empty and our current list is empty, we can
-  //      reuse the other list which is guaranteed to be immutable.
-  printer->Print(variables_,
-    "if (!other.$name$_.isEmpty()) {\n"
-    "  if ($name$_.isEmpty()) {\n"
-    "    $name$_ = other.$name$_;\n"
-    "  } else {\n"
-    "    ensure$capitalized_name$IsMutable();\n"
-    "    $name$_.addAll(other.$name$_);\n"
-    "  }\n"
-    "}\n");
+GenerateVisitCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "$name$_= visitor.visitIntList($name$_, other.$name$_);\n");
 }
 
 void RepeatedImmutableEnumFieldLiteGenerator::
@@ -831,27 +814,23 @@ GenerateDynamicMethodMakeImmutableCode(io::Printer* printer) const {
 void RepeatedImmutableEnumFieldLiteGenerator::
 GenerateParsingCode(io::Printer* printer) const {
   // Read and store the enum
+  printer->Print(variables_,
+    "if (!$is_mutable$) {\n"
+    "  $name$_ =\n"
+    "      com.google.protobuf.GeneratedMessageLite.mutableCopy($name$_);\n"
+    "}\n");
+
   if (SupportUnknownEnumValue(descriptor_->file())) {
     printer->Print(variables_,
-      "int rawValue = input.readEnum();\n"
-      "if (!$is_mutable$) {\n"
-      "  $name$_ = newIntList();\n"
-      "}\n"
-      "$name$_.addInt(rawValue);\n");
+      "$name$_.addInt(input.readEnum());\n");
   } else {
     printer->Print(variables_,
       "int rawValue = input.readEnum();\n"
       "$type$ value = $type$.forNumber(rawValue);\n"
-        "if (value == null) {\n");
-    if (PreserveUnknownFields(descriptor_->containing_type())) {
-      printer->Print(variables_,
-        "  super.mergeVarintField($number$, rawValue);\n");
-    }
-    printer->Print(variables_,
+      "if (value == null) {\n"
+      // We store the unknown value in unknown fields.
+      "  super.mergeVarintField($number$, rawValue);\n"
       "} else {\n"
-      "  if (!$is_mutable$) {\n"
-      "    $name$_ = newIntList();\n"
-      "  }\n"
       "  $name$_.addInt(rawValue);\n"
       "}\n");
   }
@@ -859,7 +838,11 @@ GenerateParsingCode(io::Printer* printer) const {
 
 void RepeatedImmutableEnumFieldLiteGenerator::
 GenerateParsingCodeFromPacked(io::Printer* printer) const {
-  // Wrap GenerateParsingCode's contents with a while loop.
+  printer->Print(variables_,
+    "if (!$is_mutable$) {\n"
+    "  $name$_ =\n"
+    "      com.google.protobuf.GeneratedMessageLite.mutableCopy($name$_);\n"
+    "}\n");
 
   printer->Print(variables_,
     "int length = input.readRawVarint32();\n"
@@ -867,7 +850,21 @@ GenerateParsingCodeFromPacked(io::Printer* printer) const {
     "while(input.getBytesUntilLimit() > 0) {\n");
   printer->Indent();
 
-  GenerateParsingCode(printer);
+  // Read and store the enum
+  if (SupportUnknownEnumValue(descriptor_->file())) {
+    printer->Print(variables_,
+      "$name$_.addInt(input.readEnum());\n");
+  } else {
+    printer->Print(variables_,
+      "int rawValue = input.readEnum();\n"
+      "$type$ value = $type$.forNumber(rawValue);\n"
+      "if (value == null) {\n"
+      // We store the unknown value in unknown fields.
+      "  super.mergeVarintField($number$, rawValue);\n"
+      "} else {\n"
+      "  $name$_.addInt(rawValue);\n"
+      "}\n");
+  }
 
   printer->Outdent();
   printer->Print(variables_,
diff --git a/src/google/protobuf/compiler/java/java_enum_field_lite.h b/src/google/protobuf/compiler/java/java_enum_field_lite.h
index 2c41c3e4..9201b8d6 100644
--- a/src/google/protobuf/compiler/java/java_enum_field_lite.h
+++ b/src/google/protobuf/compiler/java/java_enum_field_lite.h
@@ -67,7 +67,7 @@ class ImmutableEnumFieldLiteGenerator : public ImmutableFieldLiteGenerator {
   void GenerateMembers(io::Printer* printer) const;
   void GenerateBuilderMembers(io::Printer* printer) const;
   void GenerateInitializationCode(io::Printer* printer) const;
-  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateVisitCode(io::Printer* printer) const;
   void GenerateDynamicMethodMakeImmutableCode(io::Printer* printer) const;
   void GenerateParsingCode(io::Printer* printer) const;
   void GenerateParsingDoneCode(io::Printer* printer) const;
@@ -101,7 +101,7 @@ class ImmutableEnumOneofFieldLiteGenerator
 
   void GenerateMembers(io::Printer* printer) const;
   void GenerateBuilderMembers(io::Printer* printer) const;
-  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateVisitCode(io::Printer* printer) const;
   void GenerateParsingCode(io::Printer* printer) const;
   void GenerateSerializationCode(io::Printer* printer) const;
   void GenerateSerializedSizeCode(io::Printer* printer) const;
@@ -127,7 +127,7 @@ class RepeatedImmutableEnumFieldLiteGenerator
   void GenerateMembers(io::Printer* printer) const;
   void GenerateBuilderMembers(io::Printer* printer) const;
   void GenerateInitializationCode(io::Printer* printer) const;
-  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateVisitCode(io::Printer* printer) const;
   void GenerateDynamicMethodMakeImmutableCode(io::Printer* printer) const;
   void GenerateParsingCode(io::Printer* printer) const;
   void GenerateParsingCodeFromPacked(io::Printer* printer) const;
diff --git a/src/google/protobuf/compiler/java/java_field.h b/src/google/protobuf/compiler/java/java_field.h
index 0e24da24..4dd4f57f 100644
--- a/src/google/protobuf/compiler/java/java_field.h
+++ b/src/google/protobuf/compiler/java/java_field.h
@@ -105,7 +105,7 @@ class ImmutableFieldLiteGenerator {
   virtual void GenerateMembers(io::Printer* printer) const = 0;
   virtual void GenerateBuilderMembers(io::Printer* printer) const = 0;
   virtual void GenerateInitializationCode(io::Printer* printer) const = 0;
-  virtual void GenerateMergingCode(io::Printer* printer) const = 0;
+  virtual void GenerateVisitCode(io::Printer* printer) const = 0;
   virtual void GenerateDynamicMethodMakeImmutableCode(io::Printer* printer)
       const = 0;
   virtual void GenerateParsingCode(io::Printer* printer) const = 0;
diff --git a/src/google/protobuf/compiler/java/java_lazy_message_field_lite.cc b/src/google/protobuf/compiler/java/java_lazy_message_field_lite.cc
index a648f1c2..62f39302 100644
--- a/src/google/protobuf/compiler/java/java_lazy_message_field_lite.cc
+++ b/src/google/protobuf/compiler/java/java_lazy_message_field_lite.cc
@@ -182,12 +182,11 @@ GenerateInitializationCode(io::Printer* printer) const {
 }
 
 void ImmutableLazyMessageFieldLiteGenerator::
-GenerateMergingCode(io::Printer* printer) const {
+GenerateVisitCode(io::Printer* printer) const {
   printer->Print(variables_,
-    "if (other.has$capitalized_name$()) {\n"
-    "  $name$_.merge(other.$name$_);\n"
-    "  $set_has_field_bit_message$;\n"
-    "}\n");
+    "$name$_ = visitor.visitLazyMessage(\n"
+    "    has$capitalized_name$(), $name$_,\n"
+    "    other.has$capitalized_name$(), other.$name$_);\n");
 }
 
 void ImmutableLazyMessageFieldLiteGenerator::
@@ -362,14 +361,12 @@ GenerateBuilderMembers(io::Printer* printer) const {
 }
 
 void ImmutableLazyMessageOneofFieldLiteGenerator::
-GenerateMergingCode(io::Printer* printer) const {
+GenerateVisitCode(io::Printer* printer) const {
   printer->Print(variables_,
-    "if (!($has_oneof_case_message$)) {\n"
-    "  $oneof_name$_ = new $lazy_type$();\n"
-    "}\n"
-    "(($lazy_type$) $oneof_name$_).merge(\n"
-    "    ($lazy_type$) other.$oneof_name$_);\n"
-    "$set_oneof_case_message$;\n");
+    "$oneof_name$_ = visitor.visitOneofLazyMessage(\n"
+    "    $has_oneof_case_message$,\n"
+    "    ($lazy_type$) $oneof_name$_,\n"
+    "    ($lazy_type$) other.$oneof_name$_);\n");
 }
 
 void ImmutableLazyMessageOneofFieldLiteGenerator::
@@ -463,7 +460,8 @@ GenerateMembers(io::Printer* printer) const {
   printer->Print(variables_,
     "private void ensure$capitalized_name$IsMutable() {\n"
     "  if (!$is_mutable$) {\n"
-    "    $name$_ = newProtobufList($name$_);\n"
+    "    $name$_ =\n"
+    "        com.google.protobuf.GeneratedMessageLite.mutableCopy($name$_);\n"
     "   }\n"
     "}\n"
     "\n");
@@ -678,7 +676,8 @@ void RepeatedImmutableLazyMessageFieldLiteGenerator::
 GenerateParsingCode(io::Printer* printer) const {
   printer->Print(variables_,
     "if (!$is_mutable$) {\n"
-    "  $name$_ = newProtobufList();\n"
+    "  $name$_ =\n"
+    "      com.google.protobuf.GeneratedMessageLite.mutableCopy($name$_);\n"
     "}\n"
     "$name$_.add(new com.google.protobuf.LazyFieldLite(\n"
     "    extensionRegistry, input.readBytes()));\n");
diff --git a/src/google/protobuf/compiler/java/java_lazy_message_field_lite.h b/src/google/protobuf/compiler/java/java_lazy_message_field_lite.h
index e85ec0f3..47ebeb49 100644
--- a/src/google/protobuf/compiler/java/java_lazy_message_field_lite.h
+++ b/src/google/protobuf/compiler/java/java_lazy_message_field_lite.h
@@ -63,7 +63,7 @@ class ImmutableLazyMessageFieldLiteGenerator
   void GenerateMembers(io::Printer* printer) const;
   void GenerateBuilderMembers(io::Printer* printer) const;
   void GenerateInitializationCode(io::Printer* printer) const;
-  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateVisitCode(io::Printer* printer) const;
   void GenerateParsingCode(io::Printer* printer) const;
   void GenerateSerializationCode(io::Printer* printer) const;
   void GenerateSerializedSizeCode(io::Printer* printer) const;
@@ -82,7 +82,7 @@ class ImmutableLazyMessageOneofFieldLiteGenerator
 
   void GenerateMembers(io::Printer* printer) const;
   void GenerateBuilderMembers(io::Printer* printer) const;
-  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateVisitCode(io::Printer* printer) const;
   void GenerateParsingCode(io::Printer* printer) const;
   void GenerateSerializationCode(io::Printer* printer) const;
   void GenerateSerializedSizeCode(io::Printer* printer) const;
diff --git a/src/google/protobuf/compiler/java/java_map_field.cc b/src/google/protobuf/compiler/java/java_map_field.cc
index 17c3646f..2a551ca4 100644
--- a/src/google/protobuf/compiler/java/java_map_field.cc
+++ b/src/google/protobuf/compiler/java/java_map_field.cc
@@ -215,7 +215,7 @@ GenerateMembers(io::Printer* printer) const {
       "  if ($name$_ == null) {\n"
       "    return com.google.protobuf.MapField$lite$.emptyMapField(\n"
       "        $map_field_parameter$);\n"
-      " }\n"
+      "  }\n"
       "  return $name$_;\n"
       "}\n");
   if (GetJavaType(ValueField(descriptor_)) == JAVATYPE_ENUM) {
@@ -270,7 +270,7 @@ GenerateBuilderMembers(io::Printer* printer) const {
       "  if ($name$_ == null) {\n"
       "    return com.google.protobuf.MapField$lite$.emptyMapField(\n"
       "        $map_field_parameter$);\n"
-      " }\n"
+      "  }\n"
       "  return $name$_;\n"
       "}\n"
       "private com.google.protobuf.MapField$lite$<$type_parameters$>\n"
diff --git a/src/google/protobuf/compiler/java/java_map_field_lite.cc b/src/google/protobuf/compiler/java/java_map_field_lite.cc
index 6bdebb0d..b80d4139 100644
--- a/src/google/protobuf/compiler/java/java_map_field_lite.cc
+++ b/src/google/protobuf/compiler/java/java_map_field_lite.cc
@@ -374,10 +374,10 @@ GenerateInitializationCode(io::Printer* printer) const {
 }
 
 void ImmutableMapFieldLiteGenerator::
-GenerateMergingCode(io::Printer* printer) const {
+GenerateVisitCode(io::Printer* printer) const {
   printer->Print(
       variables_,
-      "internalGetMutable$capitalized_name$().mergeFrom(\n"
+      "$name$_ = visitor.visitMap(internalGetMutable$capitalized_name$(),\n"
       "    other.internalGet$capitalized_name$());\n");
 }
 
diff --git a/src/google/protobuf/compiler/java/java_map_field_lite.h b/src/google/protobuf/compiler/java/java_map_field_lite.h
index a09cd536..555b5c5b 100644
--- a/src/google/protobuf/compiler/java/java_map_field_lite.h
+++ b/src/google/protobuf/compiler/java/java_map_field_lite.h
@@ -52,7 +52,7 @@ class ImmutableMapFieldLiteGenerator : public ImmutableFieldLiteGenerator {
   void GenerateMembers(io::Printer* printer) const;
   void GenerateBuilderMembers(io::Printer* printer) const;
   void GenerateInitializationCode(io::Printer* printer) const;
-  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateVisitCode(io::Printer* printer) const;
   void GenerateDynamicMethodMakeImmutableCode(io::Printer* printer) const;
   void GenerateParsingCode(io::Printer* printer) const;
   void GenerateParsingDoneCode(io::Printer* printer) const;
diff --git a/src/google/protobuf/compiler/java/java_message.cc b/src/google/protobuf/compiler/java/java_message.cc
index dfd8ad08..4c474a48 100644
--- a/src/google/protobuf/compiler/java/java_message.cc
+++ b/src/google/protobuf/compiler/java/java_message.cc
@@ -89,7 +89,6 @@ MessageGenerator::MessageGenerator(const Descriptor* descriptor)
 MessageGenerator::~MessageGenerator() {}
 
 // ===================================================================
-// TODO(api): Move this class to a separate immutable_message.cc file.
 ImmutableMessageGenerator::ImmutableMessageGenerator(
     const Descriptor* descriptor, Context* context)
   : MessageGenerator(descriptor), context_(context),
@@ -1226,7 +1225,8 @@ GenerateParsingConstructor(io::Printer* printer) {
       "default: {\n"
       "  if (!input.skipField(tag)) {\n"
       "    done = true;\n"  // it's an endgroup tag
-      "  }\n"
+      "  }\n");
+    printer->Print(
       "  break;\n"
       "}\n");
   }
diff --git a/src/google/protobuf/compiler/java/java_message_field_lite.cc b/src/google/protobuf/compiler/java/java_message_field_lite.cc
index 049679df..14281816 100644
--- a/src/google/protobuf/compiler/java/java_message_field_lite.cc
+++ b/src/google/protobuf/compiler/java/java_message_field_lite.cc
@@ -286,11 +286,9 @@ void ImmutableMessageFieldLiteGenerator::
 GenerateInitializationCode(io::Printer* printer) const {}
 
 void ImmutableMessageFieldLiteGenerator::
-GenerateMergingCode(io::Printer* printer) const {
+GenerateVisitCode(io::Printer* printer) const {
   printer->Print(variables_,
-    "if (other.has$capitalized_name$()) {\n"
-    "  merge$capitalized_name$(other.get$capitalized_name$());\n"
-    "}\n");
+    "$name$_ = visitor.visitMessage($name$_, other.$name$_);\n");
 }
 
 void ImmutableMessageFieldLiteGenerator::
@@ -300,11 +298,18 @@ GenerateDynamicMethodMakeImmutableCode(io::Printer* printer) const {
 
 void ImmutableMessageFieldLiteGenerator::
 GenerateParsingCode(io::Printer* printer) const {
-  printer->Print(variables_,
-    "$type$.Builder subBuilder = null;\n"
-    "if ($is_field_present_message$) {\n"
-    "  subBuilder = $name$_.toBuilder();\n"
-    "}\n");
+  // TODO(dweis): Update this code to avoid the builder allocation and instead
+  // only allocate a submessage that isn't made immutable. Rely on the top
+  // message calling makeImmutable once done to actually traverse the tree and
+  // finalize state. This will avoid:
+  // - transitive builder allocations
+  // - the extra transitive iteration for streamed fields
+  // - reallocations for copying repeated fields
+  printer->Print(variables_,
+      "$type$.Builder subBuilder = null;\n"
+      "if ($is_field_present_message$) {\n"
+      "  subBuilder = $name$_.toBuilder();\n"
+      "}\n");
 
     if (GetType(descriptor_) == FieldDescriptor::TYPE_GROUP) {
       printer->Print(variables_,
@@ -504,9 +509,12 @@ GenerateBuilderMembers(io::Printer* printer) const {
 }
 
 void ImmutableMessageOneofFieldLiteGenerator::
-GenerateMergingCode(io::Printer* printer) const {
+GenerateVisitCode(io::Printer* printer) const {
   printer->Print(variables_,
-    "merge$capitalized_name$(other.get$capitalized_name$());\n");
+    "$oneof_name$_ = visitor.visitOneofMessage(\n"
+    "    $has_oneof_case_message$,\n"
+    "    $oneof_name$_,\n"
+    "    other.$oneof_name$_);\n");
 }
 
 void ImmutableMessageOneofFieldLiteGenerator::
@@ -633,7 +641,8 @@ GenerateMembers(io::Printer* printer) const {
   printer->Print(variables_,
     "private void ensure$capitalized_name$IsMutable() {\n"
     "  if (!$is_mutable$) {\n"
-    "    $name$_ = newProtobufList($name$_);\n"
+    "    $name$_ =\n"
+    "        com.google.protobuf.GeneratedMessageLite.mutableCopy($name$_);\n"
     "   }\n"
     "}\n"
     "\n");
@@ -851,21 +860,9 @@ GenerateInitializationCode(io::Printer* printer) const {
 }
 
 void RepeatedImmutableMessageFieldLiteGenerator::
-GenerateMergingCode(io::Printer* printer) const {
-  // The code below does two optimizations (non-nested builder case):
-  //   1. If the other list is empty, there's nothing to do. This ensures we
-  //      don't allocate a new array if we already have an immutable one.
-  //   2. If the other list is non-empty and our current list is empty, we can
-  //      reuse the other list which is guaranteed to be immutable.
-  printer->Print(variables_,
-    "if (!other.$name$_.isEmpty()) {\n"
-    "  if ($name$_.isEmpty()) {\n"
-    "    $name$_ = other.$name$_;\n"
-    "  } else {\n"
-    "    ensure$capitalized_name$IsMutable();\n"
-    "    $name$_.addAll(other.$name$_);\n"
-    "  }\n"
-    "}\n");
+GenerateVisitCode(io::Printer* printer) const {
+  printer->Print(variables_,
+      "$name$_= visitor.visitList($name$_, other.$name$_);\n");
 }
 
 void RepeatedImmutableMessageFieldLiteGenerator::
@@ -878,7 +875,8 @@ void RepeatedImmutableMessageFieldLiteGenerator::
 GenerateParsingCode(io::Printer* printer) const {
   printer->Print(variables_,
     "if (!$is_mutable$) {\n"
-    "  $name$_ = newProtobufList();\n"
+    "  $name$_ =\n"
+    "      com.google.protobuf.GeneratedMessageLite.mutableCopy($name$_);\n"
     "}\n");
 
     if (GetType(descriptor_) == FieldDescriptor::TYPE_GROUP) {
diff --git a/src/google/protobuf/compiler/java/java_message_field_lite.h b/src/google/protobuf/compiler/java/java_message_field_lite.h
index ae26c06a..61321547 100644
--- a/src/google/protobuf/compiler/java/java_message_field_lite.h
+++ b/src/google/protobuf/compiler/java/java_message_field_lite.h
@@ -67,7 +67,7 @@ class ImmutableMessageFieldLiteGenerator : public ImmutableFieldLiteGenerator {
   void GenerateMembers(io::Printer* printer) const;
   void GenerateBuilderMembers(io::Printer* printer) const;
   void GenerateInitializationCode(io::Printer* printer) const;
-  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateVisitCode(io::Printer* printer) const;
   void GenerateDynamicMethodMakeImmutableCode(io::Printer* printer) const;
   void GenerateParsingCode(io::Printer* printer) const;
   void GenerateParsingDoneCode(io::Printer* printer) const;
@@ -101,7 +101,7 @@ class ImmutableMessageOneofFieldLiteGenerator
 
   void GenerateMembers(io::Printer* printer) const;
   void GenerateBuilderMembers(io::Printer* printer) const;
-  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateVisitCode(io::Printer* printer) const;
   void GenerateParsingCode(io::Printer* printer) const;
   void GenerateSerializationCode(io::Printer* printer) const;
   void GenerateSerializedSizeCode(io::Printer* printer) const;
@@ -125,7 +125,7 @@ class RepeatedImmutableMessageFieldLiteGenerator
   void GenerateMembers(io::Printer* printer) const;
   void GenerateBuilderMembers(io::Printer* printer) const;
   void GenerateInitializationCode(io::Printer* printer) const;
-  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateVisitCode(io::Printer* printer) const;
   void GenerateDynamicMethodMakeImmutableCode(io::Printer* printer) const;
   void GenerateParsingCode(io::Printer* printer) const;
   void GenerateParsingDoneCode(io::Printer* printer) const;
diff --git a/src/google/protobuf/compiler/java/java_message_lite.cc b/src/google/protobuf/compiler/java/java_message_lite.cc
index 14cc908b..d4d2593a 100644
--- a/src/google/protobuf/compiler/java/java_message_lite.cc
+++ b/src/google/protobuf/compiler/java/java_message_lite.cc
@@ -199,7 +199,7 @@ void ImmutableMessageLiteGenerator::Generate(io::Printer* printer) {
   printer->Indent();
 
 
-  GenerateParsingConstructor(printer);
+  GenerateConstructor(printer);
 
   // Nested types
   for (int i = 0; i < descriptor_->enum_type_count(); i++) {
@@ -322,10 +322,6 @@ void ImmutableMessageLiteGenerator::Generate(io::Printer* printer) {
 
   GenerateMessageSerializationMethods(printer);
 
-  if (HasEqualsAndHashCode(descriptor_)) {
-    GenerateEqualsAndHashCode(printer);
-  }
-
   GenerateParseFromMethods(printer);
   GenerateBuilder(printer);
 
@@ -342,16 +338,8 @@ void ImmutableMessageLiteGenerator::Generate(io::Printer* printer) {
     "    com.google.protobuf.GeneratedMessageLite.MethodToInvoke method,\n"
     "    Object arg0, Object arg1) {\n"
     "  switch (method) {\n"
-    "    case PARSE_PARTIAL_FROM: {\n"
-    "      return new $classname$("
-    "          (com.google.protobuf.CodedInputStream) arg0,\n"
-    "          (com.google.protobuf.ExtensionRegistryLite) arg1);\n"
-    "    }\n"
-    "    case NEW_INSTANCE: {\n"
-    "      return new $classname$(\n"
-    "          com.google.protobuf.Internal.EMPTY_CODED_INPUT_STREAM,\n"
-    "          com.google.protobuf.ExtensionRegistryLite\n"
-    "              .getEmptyRegistry());\n"
+    "    case NEW_MUTABLE_INSTANCE: {\n"
+    "      return new $classname$();\n"
     "    }\n",
     "classname", name_resolver_->GetImmutableClassName(descriptor_));
 
@@ -382,10 +370,18 @@ void ImmutableMessageLiteGenerator::Generate(io::Printer* printer) {
 
   printer->Print(
     "}\n"
-    "case MERGE_FROM: {\n");
+    "case VISIT: {\n");
 
   printer->Indent();
-  GenerateDynamicMethodMergeFrom(printer);
+  GenerateDynamicMethodVisit(printer);
+  printer->Outdent();
+
+  printer->Print(
+    "}\n"
+    "case MERGE_FROM_STREAM: {\n");
+
+  printer->Indent();
+  GenerateDynamicMethodMergeFromStream(printer);
   printer->Outdent();
 
   printer->Print(
@@ -433,11 +429,8 @@ void ImmutableMessageLiteGenerator::Generate(io::Printer* printer) {
 
   printer->Print(
     "static {\n"
-    "  DEFAULT_INSTANCE = new $classname$(\n"
-    "      com.google.protobuf.Internal\n"
-    "          .EMPTY_CODED_INPUT_STREAM,\n"
-    "      com.google.protobuf.ExtensionRegistryLite\n"
-    "          .getEmptyRegistry());\n"
+    "  DEFAULT_INSTANCE = new $classname$();\n"
+    "  DEFAULT_INSTANCE.makeImmutable();\n"
     "}\n"
     "\n",
     "classname", descriptor_->name());
@@ -802,11 +795,13 @@ void ImmutableMessageLiteGenerator::GenerateDynamicMethodIsInitialized(
 
 void ImmutableMessageLiteGenerator::GenerateDynamicMethodMakeImmutable(
     io::Printer* printer) {
+
   // Output generation code for each field.
   for (int i = 0; i < descriptor_->field_count(); i++) {
     field_generators_.get(descriptor_->field(i))
         .GenerateDynamicMethodMakeImmutableCode(printer);
   }
+
   printer->Print(
     "return null;\n");
 }
@@ -821,19 +816,17 @@ void ImmutableMessageLiteGenerator::GenerateDynamicMethodNewBuilder(
 
 // ===================================================================
 
-void ImmutableMessageLiteGenerator::GenerateDynamicMethodMergeFrom(
+void ImmutableMessageLiteGenerator::GenerateDynamicMethodVisit(
     io::Printer* printer) {
   printer->Print(
-    // Optimization:  If other is the default instance, we know none of its
-    //   fields are set so we can skip the merge.
-    "if (arg0 == $classname$.getDefaultInstance()) return this;\n"
-    "$classname$ other = ($classname$) arg0;\n",
+    "Visitor visitor = (Visitor) arg0;\n"
+    "$classname$ other = ($classname$) arg1;\n",
     "classname", name_resolver_->GetImmutableClassName(descriptor_));
 
   for (int i = 0; i < descriptor_->field_count(); i++) {
     if (!descriptor_->field(i)->containing_oneof()) {
       field_generators_.get(
-          descriptor_->field(i)).GenerateMergingCode(printer);
+          descriptor_->field(i)).GenerateVisitCode(printer);
     }
   }
 
@@ -852,7 +845,7 @@ void ImmutableMessageLiteGenerator::GenerateDynamicMethodMergeFrom(
         "field_name",
         ToUpper(field->name()));
       printer->Indent();
-      field_generators_.get(field).GenerateMergingCode(printer);
+      field_generators_.get(field).GenerateVisitCode(printer);
       printer->Print(
           "break;\n");
       printer->Outdent();
@@ -861,254 +854,66 @@ void ImmutableMessageLiteGenerator::GenerateDynamicMethodMergeFrom(
     }
     printer->Print(
       "case $cap_oneof_name$_NOT_SET: {\n"
+      "  visitor.visitOneofNotSet($oneof_name$Case_ != 0);\n"
       "  break;\n"
       "}\n",
       "cap_oneof_name",
       ToUpper(context_->GetOneofGeneratorInfo(
-          descriptor_->oneof_decl(i))->name));
-    printer->Outdent();
-    printer->Print(
-      "}\n");
-  }
-
-  // if message type has extensions
-  if (descriptor_->extension_range_count() > 0) {
-    printer->Print(
-      "this.mergeExtensionFields(other);\n");
-  }
-
-  if (PreserveUnknownFields(descriptor_)) {
-    printer->Print(
-      "this.mergeUnknownFields(other.unknownFields);\n");
-  }
-
-  printer->Print(
-    "return this;\n");
-}
-
-// ===================================================================
-
-namespace {
-bool CheckHasBitsForEqualsAndHashCode(const FieldDescriptor* field) {
-  if (field->is_repeated()) {
-    return false;
-  }
-  if (SupportFieldPresence(field->file())) {
-    return true;
-  }
-  return GetJavaType(field) == JAVATYPE_MESSAGE &&
-      field->containing_oneof() == NULL;
-}
-}  // namespace
-
-void ImmutableMessageLiteGenerator::
-GenerateEqualsAndHashCode(io::Printer* printer) {
-  printer->Print(
-    "@java.lang.Override\n"
-    "public boolean equals(final java.lang.Object obj) {\n");
-  printer->Indent();
-  printer->Print(
-    "if (obj == this) {\n"
-    " return true;\n"
-    "}\n"
-    "if (!(obj instanceof $classname$)) {\n"
-    "  return super.equals(obj);\n"
-    "}\n"
-    "$classname$ other = ($classname$) obj;\n"
-    "\n",
-    "classname", name_resolver_->GetImmutableClassName(descriptor_));
-
-  printer->Print("boolean result = true;\n");
-  // Compare non-oneofs.
-  for (int i = 0; i < descriptor_->field_count(); i++) {
-    const FieldDescriptor* field = descriptor_->field(i);
-    if (field->containing_oneof() == NULL) {
-      const FieldGeneratorInfo* info = context_->GetFieldGeneratorInfo(field);
-      bool check_has_bits = CheckHasBitsForEqualsAndHashCode(field);
-      if (check_has_bits) {
-        printer->Print(
-          "result = result && (has$name$() == other.has$name$());\n"
-          "if (has$name$()) {\n",
-          "name", info->capitalized_name);
-        printer->Indent();
-      }
-      field_generators_.get(field).GenerateEqualsCode(printer);
-      if (check_has_bits) {
-        printer->Outdent();
-        printer->Print(
-          "}\n");
-      }
-    }
-  }
-
-  // Compare oneofs.
-  for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
-    printer->Print(
-      "result = result && get$oneof_capitalized_name$Case().equals(\n"
-      "    other.get$oneof_capitalized_name$Case());\n",
-      "oneof_capitalized_name",
-      context_->GetOneofGeneratorInfo(
-          descriptor_->oneof_decl(i))->capitalized_name);
-    printer->Print(
-      "if (!result) return false;\n"
-      "switch ($oneof_name$Case_) {\n",
+          descriptor_->oneof_decl(i))->name),
       "oneof_name",
       context_->GetOneofGeneratorInfo(
           descriptor_->oneof_decl(i))->name);
-    printer->Indent();
-    for (int j = 0; j < descriptor_->oneof_decl(i)->field_count(); j++) {
-      const FieldDescriptor* field = descriptor_->oneof_decl(i)->field(j);
-      printer->Print(
-        "case $field_number$:\n",
-        "field_number",
-        SimpleItoa(field->number()));
-      printer->Indent();
-      field_generators_.get(field).GenerateEqualsCode(printer);
-      printer->Print("break;\n");
-      printer->Outdent();
-    }
-    printer->Print(
-      "case 0:\n"
-      "default:\n");
     printer->Outdent();
-    printer->Print("}\n");
-  }
-
-  if (PreserveUnknownFields(descriptor_)) {
-    // Always consider unknown fields for equality. This will sometimes return
-    // false for non-canonical ordering when running in LITE_RUNTIME but it's
-    // the best we can do.
     printer->Print(
-      "result = result && unknownFields.equals(other.unknownFields);\n");
+      "}\n");
   }
-  printer->Print(
-    "return result;\n");
-  printer->Outdent();
-  printer->Print(
-    "}\n"
-    "\n");
 
   printer->Print(
-    "@java.lang.Override\n"
-    "public int hashCode() {\n");
-  printer->Indent();
-  printer->Print(
-    "if (memoizedHashCode != 0) {\n");
+    "if (visitor == com.google.protobuf.GeneratedMessageLite.MergeFromVisitor\n"
+    "    .INSTANCE) {\n");
   printer->Indent();
-  printer->Print(
-    "return memoizedHashCode;\n");
-  printer->Outdent();
-  printer->Print(
-    "}\n"
-    "int hash = 41;\n");
-
-  // Include the hash of the class so that two objects with different types
-  // but the same field values will probably have different hashes.
-  printer->Print("hash = (19 * hash) + $classname$.class.hashCode();\n",
-    "classname", name_resolver_->GetImmutableClassName(descriptor_));
+  for (int i = 0; i < descriptor_->oneof_decl_count(); ++i) {
+    const OneofDescriptor* field = descriptor_->oneof_decl(i);
+    printer->Print(
+      "if (other.$oneof_name$Case_ != 0) {\n"
+      "  $oneof_name$Case_ = other.$oneof_name$Case_;\n"
+      "}\n",
+      "oneof_name", context_->GetOneofGeneratorInfo(field)->name);
+  }
 
-  // hashCode non-oneofs.
-  for (int i = 0; i < descriptor_->field_count(); i++) {
-    const FieldDescriptor* field = descriptor_->field(i);
-    if (field->containing_oneof() == NULL) {
-      const FieldGeneratorInfo* info = context_->GetFieldGeneratorInfo(field);
-      bool check_has_bits = CheckHasBitsForEqualsAndHashCode(field);
-      if (check_has_bits) {
-        printer->Print(
-          "if (has$name$()) {\n",
-          "name", info->capitalized_name);
-        printer->Indent();
-      }
-      field_generators_.get(field).GenerateHashCode(printer);
-      if (check_has_bits) {
-        printer->Outdent();
-        printer->Print("}\n");
-      }
+  if (GenerateHasBits(descriptor_)) {
+    // Integers for bit fields.
+    int totalBits = 0;
+    for (int i = 0; i < descriptor_->field_count(); i++) {
+      totalBits += field_generators_.get(descriptor_->field(i))
+          .GetNumBitsForMessage();
     }
-  }
+    int totalInts = (totalBits + 31) / 32;
 
-  // hashCode oneofs.
-  for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
-    printer->Print(
-      "switch ($oneof_name$Case_) {\n",
-      "oneof_name",
-      context_->GetOneofGeneratorInfo(
-          descriptor_->oneof_decl(i))->name);
-    printer->Indent();
-    for (int j = 0; j < descriptor_->oneof_decl(i)->field_count(); j++) {
-      const FieldDescriptor* field = descriptor_->oneof_decl(i)->field(j);
+    for (int i = 0; i < totalInts; i++) {
       printer->Print(
-        "case $field_number$:\n",
-        "field_number",
-        SimpleItoa(field->number()));
-      printer->Indent();
-      field_generators_.get(field).GenerateHashCode(printer);
-      printer->Print("break;\n");
-      printer->Outdent();
+        "$bit_field_name$ |= other.$bit_field_name$;\n",
+        "bit_field_name", GetBitFieldName(i));
     }
-    printer->Print(
-      "case 0:\n"
-      "default:\n");
-    printer->Outdent();
-    printer->Print("}\n");
   }
-
-  printer->Print(
-    "hash = (29 * hash) + unknownFields.hashCode();\n");
-  printer->Print(
-    "memoizedHashCode = hash;\n"
-    "return hash;\n");
   printer->Outdent();
   printer->Print(
-    "}\n"
-    "\n");
-}
+    "}\n");
 
-// ===================================================================
 
-void ImmutableMessageLiteGenerator::
-GenerateExtensionRegistrationCode(io::Printer* printer) {
-  for (int i = 0; i < descriptor_->extension_count(); i++) {
-    ImmutableExtensionLiteGenerator(descriptor_->extension(i), context_)
-      .GenerateRegistrationCode(printer);
-  }
-
-  for (int i = 0; i < descriptor_->nested_type_count(); i++) {
-    ImmutableMessageLiteGenerator(descriptor_->nested_type(i), context_)
-      .GenerateExtensionRegistrationCode(printer);
-  }
+  printer->Print(
+    "return this;\n");
 }
 
 // ===================================================================
-void ImmutableMessageLiteGenerator::
-GenerateParsingConstructor(io::Printer* printer) {
-  google::protobuf::scoped_array<const FieldDescriptor * > sorted_fields(
-      SortFieldsByNumber(descriptor_));
-
-  printer->Print(
-      "private $classname$(\n"
-      "    com.google.protobuf.CodedInputStream input,\n"
-      "    com.google.protobuf.ExtensionRegistryLite extensionRegistry) {\n",
-      "classname", descriptor_->name());
-  printer->Indent();
-
-  // Initialize all fields to default.
-  GenerateInitializers(printer);
-
-  // Use builder bits to track mutable repeated fields.
-  int totalBuilderBits = 0;
-  for (int i = 0; i < descriptor_->field_count(); i++) {
-    const ImmutableFieldLiteGenerator& field =
-        field_generators_.get(descriptor_->field(i));
-    totalBuilderBits += field.GetNumBitsForBuilder();
-  }
-  int totalBuilderInts = (totalBuilderBits + 31) / 32;
-  for (int i = 0; i < totalBuilderInts; i++) {
-    printer->Print("int mutable_$bit_field_name$ = 0;\n",
-      "bit_field_name", GetBitFieldName(i));
-  }
 
+void ImmutableMessageLiteGenerator::GenerateDynamicMethodMergeFromStream(
+    io::Printer* printer) {
   printer->Print(
+      "com.google.protobuf.CodedInputStream input =\n"
+      "    (com.google.protobuf.CodedInputStream) arg0;\n"
+      "com.google.protobuf.ExtensionRegistryLite extensionRegistry =\n"
+      "    (com.google.protobuf.ExtensionRegistryLite) arg1;\n"
       "try {\n");
   printer->Indent();
 
@@ -1156,6 +961,8 @@ GenerateParsingConstructor(io::Printer* printer) {
       "}\n");
   }
 
+  google::protobuf::scoped_array<const FieldDescriptor * > sorted_fields(
+      SortFieldsByNumber(descriptor_));
   for (int i = 0; i < descriptor_->field_count(); i++) {
     const FieldDescriptor* field = sorted_fields[i];
     uint32 tag = WireFormatLite::MakeTag(field->number(),
@@ -1209,19 +1016,54 @@ GenerateParsingConstructor(io::Printer* printer) {
       "} finally {\n");
   printer->Indent();
 
-  // Make repeated field list immutable.
-  for (int i = 0; i < descriptor_->field_count(); i++) {
-    const FieldDescriptor* field = sorted_fields[i];
-    field_generators_.get(field).GenerateParsingDoneCode(printer);
+  printer->Outdent();
+  printer->Print(
+      "}\n");     // finally
+}
+
+// ===================================================================
+
+namespace {
+bool CheckHasBitsForEqualsAndHashCode(const FieldDescriptor* field) {
+  if (field->is_repeated()) {
+    return false;
+  }
+  if (SupportFieldPresence(field->file())) {
+    return true;
   }
+  return GetJavaType(field) == JAVATYPE_MESSAGE &&
+      field->containing_oneof() == NULL;
+}
+}  // namespace
+
+// ===================================================================
 
+void ImmutableMessageLiteGenerator::
+GenerateExtensionRegistrationCode(io::Printer* printer) {
+  for (int i = 0; i < descriptor_->extension_count(); i++) {
+    ImmutableExtensionLiteGenerator(descriptor_->extension(i), context_)
+      .GenerateRegistrationCode(printer);
+  }
+
+  for (int i = 0; i < descriptor_->nested_type_count(); i++) {
+    ImmutableMessageLiteGenerator(descriptor_->nested_type(i), context_)
+      .GenerateExtensionRegistrationCode(printer);
+  }
+}
+
+// ===================================================================
+void ImmutableMessageLiteGenerator::
+GenerateConstructor(io::Printer* printer) {
   printer->Print(
-      "doneParsing();\n");
+      "private $classname$() {\n",
+      "classname", descriptor_->name());
+  printer->Indent();
+
+  // Initialize all fields to default.
+  GenerateInitializers(printer);
 
-  printer->Outdent();
   printer->Outdent();
   printer->Print(
-      "  }\n"     // finally
       "}\n");
 }
 
diff --git a/src/google/protobuf/compiler/java/java_message_lite.h b/src/google/protobuf/compiler/java/java_message_lite.h
index c8ee99bd..292c1c56 100644
--- a/src/google/protobuf/compiler/java/java_message_lite.h
+++ b/src/google/protobuf/compiler/java/java_message_lite.h
@@ -70,12 +70,13 @@ class ImmutableMessageLiteGenerator : public MessageGenerator {
   void GenerateBuilder(io::Printer* printer);
   void GenerateDynamicMethodIsInitialized(io::Printer* printer);
   void GenerateDynamicMethodMakeImmutable(io::Printer* printer);
-  void GenerateDynamicMethodMergeFrom(io::Printer* printer);
+  void GenerateDynamicMethodVisit(io::Printer* printer);
+  void GenerateDynamicMethodMergeFromStream(io::Printer* printer);
   void GenerateDynamicMethodNewBuilder(io::Printer* printer);
   void GenerateInitializers(io::Printer* printer);
   void GenerateEqualsAndHashCode(io::Printer* printer);
   void GenerateParser(io::Printer* printer);
-  void GenerateParsingConstructor(io::Printer* printer);
+  void GenerateConstructor(io::Printer* printer);
 
   Context* context_;
   ClassNameResolver* name_resolver_;
diff --git a/src/google/protobuf/compiler/java/java_plugin_unittest.cc b/src/google/protobuf/compiler/java/java_plugin_unittest.cc
index fe527623..3e4910c8 100644
--- a/src/google/protobuf/compiler/java/java_plugin_unittest.cc
+++ b/src/google/protobuf/compiler/java/java_plugin_unittest.cc
@@ -44,9 +44,10 @@
 #include <google/protobuf/io/zero_copy_stream.h>
 #include <google/protobuf/io/printer.h>
 
+#include <google/protobuf/testing/file.h>
+#include <google/protobuf/testing/file.h>
 #include <google/protobuf/testing/googletest.h>
 #include <gtest/gtest.h>
-#include <google/protobuf/testing/file.h>
 
 namespace google {
 namespace protobuf {
diff --git a/src/google/protobuf/compiler/java/java_primitive_field_lite.cc b/src/google/protobuf/compiler/java/java_primitive_field_lite.cc
index d277e4f3..690dad12 100644
--- a/src/google/protobuf/compiler/java/java_primitive_field_lite.cc
+++ b/src/google/protobuf/compiler/java/java_primitive_field_lite.cc
@@ -86,9 +86,6 @@ void SetPrimitiveVariables(const FieldDescriptor* descriptor,
     case JAVATYPE_BOOLEAN:
       (*variables)["field_list_type"] =
           "com.google.protobuf.Internal." + capitalized_type + "List";
-      (*variables)["new_list"] = "new" + capitalized_type + "List";
-      (*variables)["new_list_with_capacity"] =
-          "new" + capitalized_type + "ListWithCapacity";
       (*variables)["empty_list"] = "empty" + capitalized_type + "List()";
       (*variables)["make_name_unmodifiable"] =
           (*variables)["name"] + "_.makeImmutable()";
@@ -98,19 +95,21 @@ void SetPrimitiveVariables(const FieldDescriptor* descriptor,
           (*variables)["name"] + "_.add" + capitalized_type;
       (*variables)["repeated_set"] =
           (*variables)["name"] + "_.set" + capitalized_type;
+      (*variables)["visit_type"] = capitalized_type;
+      (*variables)["visit_type_list"] = "visit" + capitalized_type + "List";
       break;
     default:
       (*variables)["field_list_type"] =
           "com.google.protobuf.Internal.ProtobufList<" +
           (*variables)["boxed_type"] + ">";
-      (*variables)["new_list"] = "newProtobufList";
-      (*variables)["new_list_with_capacity"] = "newProtobufListWithCapacity";
       (*variables)["empty_list"] = "emptyProtobufList()";
       (*variables)["make_name_unmodifiable"] =
           (*variables)["name"] + "_.makeImmutable()";
       (*variables)["repeated_get"] = (*variables)["name"] + "_.get";
       (*variables)["repeated_add"] = (*variables)["name"] + "_.add";
       (*variables)["repeated_set"] = (*variables)["name"] + "_.set";
+      (*variables)["visit_type"] = "ByteString";
+      (*variables)["visit_type_list"] = "visitList";
   }
 
   if (IsReferenceType(GetJavaType(descriptor))) {
@@ -297,17 +296,16 @@ GenerateBuilderClearCode(io::Printer* printer) const {
 }
 
 void ImmutablePrimitiveFieldLiteGenerator::
-GenerateMergingCode(io::Printer* printer) const {
+GenerateVisitCode(io::Printer* printer) const {
   if (SupportFieldPresence(descriptor_->file())) {
     printer->Print(variables_,
-      "if (other.has$capitalized_name$()) {\n"
-      "  set$capitalized_name$(other.get$capitalized_name$());\n"
-      "}\n");
+      "$name$_ = visitor.visit$visit_type$(\n"
+      "    has$capitalized_name$(), $name$_,\n"
+      "    other.has$capitalized_name$(), other.$name$_);\n");
   } else {
     printer->Print(variables_,
-      "if (other.get$capitalized_name$() != $default$) {\n"
-      "  set$capitalized_name$(other.get$capitalized_name$());\n"
-      "}\n");
+      "$name$_ = visitor.visit$visit_type$($name$_ != $default$, $name$_,\n"
+      "    other.$name$_ != $default$, other.$name$_);\n");
   }
 }
 
@@ -539,9 +537,10 @@ GenerateBuildingCode(io::Printer* printer) const {
 }
 
 void ImmutablePrimitiveOneofFieldLiteGenerator::
-GenerateMergingCode(io::Printer* printer) const {
+GenerateVisitCode(io::Printer* printer) const {
   printer->Print(variables_,
-    "set$capitalized_name$(other.get$capitalized_name$());\n");
+      "$oneof_name$_ = visitor.visitOneof$visit_type$(\n"
+      "    $has_oneof_case_message$, $oneof_name$_, other.$oneof_name$_);\n");
 }
 
 void ImmutablePrimitiveOneofFieldLiteGenerator::
@@ -641,7 +640,8 @@ GenerateMembers(io::Printer* printer) const {
   printer->Print(variables_,
     "private void ensure$capitalized_name$IsMutable() {\n"
     "  if (!$is_mutable$) {\n"
-    "    $name$_ = $new_list$($name$_);\n"
+    "    $name$_ =\n"
+    "        com.google.protobuf.GeneratedMessageLite.mutableCopy($name$_);\n"
     "   }\n"
     "}\n");
 
@@ -742,21 +742,9 @@ GenerateBuilderClearCode(io::Printer* printer) const {
 }
 
 void RepeatedImmutablePrimitiveFieldLiteGenerator::
-GenerateMergingCode(io::Printer* printer) const {
-  // The code below does two optimizations:
-  //   1. If the other list is empty, there's nothing to do. This ensures we
-  //      don't allocate a new array if we already have an immutable one.
-  //   2. If the other list is non-empty and our current list is empty, we can
-  //      reuse the other list which is guaranteed to be immutable.
-  printer->Print(variables_,
-    "if (!other.$name$_.isEmpty()) {\n"
-    "  if ($name$_.isEmpty()) {\n"
-    "    $name$_ = other.$name$_;\n"
-    "  } else {\n"
-    "    ensure$capitalized_name$IsMutable();\n"
-    "    $name$_.addAll(other.$name$_);\n"
-    "  }\n"
-    "}\n");
+GenerateVisitCode(io::Printer* printer) const {
+  printer->Print(variables_,
+      "$name$_= visitor.$visit_type_list$($name$_, other.$name$_);\n");
 }
 
 void RepeatedImmutablePrimitiveFieldLiteGenerator::
@@ -777,7 +765,8 @@ GenerateParsingCode(io::Printer* printer) const {
   // TODO(dweis): Scan the input buffer to count and ensure capacity.
   printer->Print(variables_,
     "if (!$is_mutable$) {\n"
-    "  $name$_ = $new_list$();\n"
+    "  $name$_ =\n"
+    "      com.google.protobuf.GeneratedMessageLite.mutableCopy($name$_);\n"
     "}\n"
     "$repeated_add$(input.read$capitalized_type$());\n");
 }
@@ -794,10 +783,13 @@ GenerateParsingCodeFromPacked(io::Printer* printer) const {
     // TODO(dweis): Scan the input buffer to count, then initialize
     // appropriately.
     printer->Print(variables_,
-      "  $name$_ = $new_list$();\n");
+      "  $name$_ =\n"
+      "      com.google.protobuf.GeneratedMessageLite.mutableCopy($name$_);\n");
   } else {
     printer->Print(variables_,
-      "  $name$_ = $new_list_with_capacity$(length/$fixed_size$);\n");
+      "  final int currentSize = $name$_.size();\n"
+      "  $name$_ = $name$_.mutableCopyWithCapacity(\n"
+      "      currentSize + (length/$fixed_size$));\n");
   }
 
   // TODO(dweis): Scan the input buffer to count and ensure capacity.
diff --git a/src/google/protobuf/compiler/java/java_primitive_field_lite.h b/src/google/protobuf/compiler/java/java_primitive_field_lite.h
index ad603c2a..6cfbbb98 100644
--- a/src/google/protobuf/compiler/java/java_primitive_field_lite.h
+++ b/src/google/protobuf/compiler/java/java_primitive_field_lite.h
@@ -69,7 +69,7 @@ class ImmutablePrimitiveFieldLiteGenerator
   void GenerateBuilderMembers(io::Printer* printer) const;
   void GenerateInitializationCode(io::Printer* printer) const;
   void GenerateBuilderClearCode(io::Printer* printer) const;
-  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateVisitCode(io::Printer* printer) const;
   void GenerateBuildingCode(io::Printer* printer) const;
   void GenerateDynamicMethodMakeImmutableCode(io::Printer* printer) const;
   void GenerateParsingCode(io::Printer* printer) const;
@@ -105,7 +105,7 @@ class ImmutablePrimitiveOneofFieldLiteGenerator
   void GenerateMembers(io::Printer* printer) const;
   void GenerateBuilderMembers(io::Printer* printer) const;
   void GenerateBuildingCode(io::Printer* printer) const;
-  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateVisitCode(io::Printer* printer) const;
   void GenerateParsingCode(io::Printer* printer) const;
   void GenerateSerializationCode(io::Printer* printer) const;
   void GenerateSerializedSizeCode(io::Printer* printer) const;
@@ -130,7 +130,7 @@ class RepeatedImmutablePrimitiveFieldLiteGenerator
   void GenerateBuilderMembers(io::Printer* printer) const;
   void GenerateInitializationCode(io::Printer* printer) const;
   void GenerateBuilderClearCode(io::Printer* printer) const;
-  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateVisitCode(io::Printer* printer) const;
   void GenerateBuildingCode(io::Printer* printer) const;
   void GenerateDynamicMethodMakeImmutableCode(io::Printer* printer) const;
   void GenerateParsingCode(io::Printer* printer) const;
diff --git a/src/google/protobuf/compiler/java/java_string_field_lite.cc b/src/google/protobuf/compiler/java/java_string_field_lite.cc
index 9012ab5e..0b92c021 100644
--- a/src/google/protobuf/compiler/java/java_string_field_lite.cc
+++ b/src/google/protobuf/compiler/java/java_string_field_lite.cc
@@ -299,20 +299,16 @@ GenerateInitializationCode(io::Printer* printer) const {
 }
 
 void ImmutableStringFieldLiteGenerator::
-GenerateMergingCode(io::Printer* printer) const {
+GenerateVisitCode(io::Printer* printer) const {
   if (SupportFieldPresence(descriptor_->file())) {
-    // Allow a slight breach of abstraction here in order to avoid forcing
-    // all string fields to Strings when copying fields from a Message.
     printer->Print(variables_,
-      "if (other.has$capitalized_name$()) {\n"
-      "  $set_has_field_bit_message$\n"
-      "  $name$_ = other.$name$_;\n"
-      "}\n");
+      "$name$_ = visitor.visitString(\n"
+      "    has$capitalized_name$(), $name$_,\n"
+      "    other.has$capitalized_name$(), other.$name$_);\n");
   } else {
     printer->Print(variables_,
-      "if (!other.get$capitalized_name$().isEmpty()) {\n"
-      "  $name$_ = other.$name$_;\n"
-      "}\n");
+      "$name$_ = visitor.visitString(!$name$_.isEmpty(), $name$_,\n"
+      "    !other.$name$_.isEmpty(), other.$name$_);\n");
   }
 }
 
@@ -519,12 +515,10 @@ GenerateBuilderMembers(io::Printer* printer) const {
 }
 
 void ImmutableStringOneofFieldLiteGenerator::
-GenerateMergingCode(io::Printer* printer) const {
-  // Allow a slight breach of abstraction here in order to avoid forcing
-  // all string fields to Strings when copying fields from a Message.
+GenerateVisitCode(io::Printer* printer) const {
   printer->Print(variables_,
-    "$set_oneof_case_message$;\n"
-    "$oneof_name$_ = other.$oneof_name$_;\n");
+    "$oneof_name$_ = visitor.visitOneofString(\n"
+    "   $has_oneof_case_message$, $oneof_name$_, other.$oneof_name$_);\n");
 }
 
 void ImmutableStringOneofFieldLiteGenerator::
@@ -645,8 +639,8 @@ GenerateMembers(io::Printer* printer) const {
   printer->Print(variables_,
     "private void ensure$capitalized_name$IsMutable() {\n"
     "  if (!$is_mutable$) {\n"
-    "    $name$_ = com.google.protobuf.GeneratedMessageLite.newProtobufList(\n"
-    "        $name$_);\n"
+    "    $name$_ =\n"
+    "        com.google.protobuf.GeneratedMessageLite.mutableCopy($name$_);\n"
     "   }\n"
     "}\n");
 
@@ -773,21 +767,9 @@ GenerateInitializationCode(io::Printer* printer) const {
 }
 
 void RepeatedImmutableStringFieldLiteGenerator::
-GenerateMergingCode(io::Printer* printer) const {
-  // The code below does two optimizations:
-  //   1. If the other list is empty, there's nothing to do. This ensures we
-  //      don't allocate a new array if we already have an immutable one.
-  //   2. If the other list is non-empty and our current list is empty, we can
-  //      reuse the other list which is guaranteed to be immutable.
-  printer->Print(variables_,
-    "if (!other.$name$_.isEmpty()) {\n"
-    "  if ($name$_.isEmpty()) {\n"
-    "    $name$_ = other.$name$_;\n"
-    "  } else {\n"
-    "    ensure$capitalized_name$IsMutable();\n"
-    "    $name$_.addAll(other.$name$_);\n"
-    "  }\n"
-    "}\n");
+GenerateVisitCode(io::Printer* printer) const {
+  printer->Print(variables_,
+      "$name$_= visitor.visitList($name$_, other.$name$_);\n");
 }
 
 void RepeatedImmutableStringFieldLiteGenerator::
@@ -811,7 +793,8 @@ GenerateParsingCode(io::Printer* printer) const {
   }
   printer->Print(variables_,
     "if (!$is_mutable$) {\n"
-    "  $name$_ = com.google.protobuf.GeneratedMessageLite.newProtobufList();\n"
+    "  $name$_ =\n"
+    "      com.google.protobuf.GeneratedMessageLite.mutableCopy($name$_);\n"
     "}\n");
   printer->Print(variables_,
     "$name$_.add(s);\n");
diff --git a/src/google/protobuf/compiler/java/java_string_field_lite.h b/src/google/protobuf/compiler/java/java_string_field_lite.h
index 4d9b4bd7..4148aa4d 100644
--- a/src/google/protobuf/compiler/java/java_string_field_lite.h
+++ b/src/google/protobuf/compiler/java/java_string_field_lite.h
@@ -68,7 +68,7 @@ class ImmutableStringFieldLiteGenerator : public ImmutableFieldLiteGenerator {
   void GenerateMembers(io::Printer* printer) const;
   void GenerateBuilderMembers(io::Printer* printer) const;
   void GenerateInitializationCode(io::Printer* printer) const;
-  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateVisitCode(io::Printer* printer) const;
   void GenerateDynamicMethodMakeImmutableCode(io::Printer* printer) const;
   void GenerateParsingCode(io::Printer* printer) const;
   void GenerateParsingDoneCode(io::Printer* printer) const;
@@ -103,7 +103,7 @@ class ImmutableStringOneofFieldLiteGenerator
  private:
   void GenerateMembers(io::Printer* printer) const;
   void GenerateBuilderMembers(io::Printer* printer) const;
-  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateVisitCode(io::Printer* printer) const;
   void GenerateParsingCode(io::Printer* printer) const;
   void GenerateSerializationCode(io::Printer* printer) const;
   void GenerateSerializedSizeCode(io::Printer* printer) const;
@@ -126,7 +126,7 @@ class RepeatedImmutableStringFieldLiteGenerator
   void GenerateMembers(io::Printer* printer) const;
   void GenerateBuilderMembers(io::Printer* printer) const;
   void GenerateInitializationCode(io::Printer* printer) const;
-  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateVisitCode(io::Printer* printer) const;
   void GenerateDynamicMethodMakeImmutableCode(io::Printer* printer) const;
   void GenerateParsingCode(io::Printer* printer) const;
   void GenerateParsingDoneCode(io::Printer* printer) const;