Introduce span with line context

test/location_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:unittest/unittest.dart';
 import 'package:source_span/source_span.dart';
 
 main() {
   var location;
   setUp(() {
-    location = new SourceLocation(15,
-        line: 2, column: 6, sourceUrl: "foo.dart");
+    location =
+        new SourceLocation(15, line: 2, column: 6, sourceUrl: "foo.dart");
   });
 
   group('errors', () {
     group('for new SourceLocation()', () {
       test('offset may not be negative', () {
         expect(() => new SourceLocation(-1), throwsRangeError);
       });
 
       test('line may not be negative', () {
         expect(() => new SourceLocation(0, line: -1), throwsRangeError);
       });
 
       test('column may not be negative', () {
         expect(() => new SourceLocation(0, column: -1), throwsRangeError);
       });
     });
 
     test('for distance() source URLs must match', () {
-      expect(() => location.distance(new SourceLocation(0)),
-          throwsArgumentError);
+      expect(
+          () => location.distance(new SourceLocation(0)), throwsArgumentError);
     });
 
     test('for compareTo() source URLs must match', () {
-      expect(() => location.compareTo(new SourceLocation(0)),
-          throwsArgumentError);
+      expect(
+          () => location.compareTo(new SourceLocation(0)), throwsArgumentError);
     });
   });
 
   test('fields work correctly', () {
     expect(location.sourceUrl, equals(Uri.parse("foo.dart")));
     expect(location.offset, equals(15));
     expect(location.line, equals(2));
     expect(location.column, equals(6));
   });
 
@@ skipping 26 matching lines @@
       var other = new SourceLocation(20, sourceUrl: "foo.dart");
       expect(location.compareTo(other), lessThan(0));
       expect(other.compareTo(location), greaterThan(0));
     });
 
     test("considers equal locations equal", () {
       expect(location.compareTo(location), equals(0));
     });
   });
 
-
   group("equality", () {
     test("two locations with the same offset and source are equal", () {
       var other = new SourceLocation(15, sourceUrl: "foo.dart");
       expect(location, equals(other));
     });
 
     test("a different offset isn't equal", () {
       var other = new SourceLocation(10, sourceUrl: "foo.dart");
       expect(location, isNot(equals(other)));
     });
 
     test("a different source isn't equal", () {
       var other = new SourceLocation(15, sourceUrl: "bar.dart");
       expect(location, isNot(equals(other)));
     });
   });
 }