Crash on field tags

// Copyright (c) 2015, Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

syntax = "proto3";

package google.api;

import "google/api/http.proto";
import "google/protobuf/descriptor.proto";

option go_package = "google.golang.org/genproto/googleapis/api/annotations;annotations";
option java_multiple_files = true;
option java_outer_classname = "AnnotationsProto";
option java_package = "com.google.api";
option objc_class_prefix = "GAPI";

extend google.protobuf.MethodOptions {
  // See `HttpRule`.
  HttpRule http = 72295728;
}

Cause: multiple fields share tag 72295728:
  1. http (/Users/tolu/src/kampus_idl/idl/google/api/annotations.proto:30:3)
  2. http (/Users/tolu/src/kampus_idl/idl/google/api/annotations.proto:30:3)
  for message google.protobuf.MethodOptions (google/protobuf/descriptor.proto:689:1)
multiple fields share name http:
  1. http (/Users/tolu/src/kampus_idl/idl/google/api/annotations.proto:30:3)
  2. http (/Users/tolu/src/kampus_idl/idl/google/api/annotations.proto:30:3)
  for message google.protobuf.MethodOptions (google/protobuf/descriptor.proto:689:1)

I'm getting errors that multiple fields share the same tag, but the two fields it's referring are the same.

Start by reproducing the report with annotations.proto, including its imports of google/api/http.proto and google/protobuf/descriptor.proto. Inspect the compiler path that reports duplicate tags and names for google.protobuf.MethodOptions; done means the reported input no longer crashes or incorrectly treats the same field declaration as two fields.