fix analyzer warnings
diff --git a/bin/show_inferred_types.dart b/bin/show_inferred_types.dart
index 1981a6f..6d611e3 100644
--- a/bin/show_inferred_types.dart
+++ b/bin/show_inferred_types.dart
@@ -8,7 +8,7 @@
 import 'dart:convert';
 import 'dart:io';
 
-import 'package:dart2js_info/info.dart';
+import 'package:dart2js_info/json_info_codec.dart';
 import 'package:dart2js_info/src/util.dart';
 
 main(args) {
diff --git a/lib/src/binary/source.dart b/lib/src/binary/source.dart
index 5aee23b..5ada983 100644
--- a/lib/src/binary/source.dart
+++ b/lib/src/binary/source.dart
@@ -293,7 +293,4 @@
         "Expected one of $values, found index $index.");
     return values[index];
   }
-
-  @override
-  String get _errorContext => ' Offset $_byteOffset in ${_bytes.length}.';
 }
diff --git a/lib/src/io.dart b/lib/src/io.dart
index dde9bee..9002282 100644
--- a/lib/src/io.dart
+++ b/lib/src/io.dart
@@ -3,6 +3,7 @@
 import 'dart:io';
 
 import 'package:dart2js_info/info.dart';
+import 'package:dart2js_info/json_info_codec.dart';
 
 Future<AllInfo> infoFromFile(String fileName) async {
   var file = await new File(fileName).readAsString();