Introduce span with line context

test/file_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 file;
   setUp(() {
@@ skipping 69 matching lines @@
         expect(() => file.getOffset(1, -1), throwsRangeError);
       });
 
       test("line may not be outside the file", () {
         expect(() => file.getOffset(100), throwsRangeError);
       });
 
       test("column may not be outside the file", () {
         expect(() => file.getOffset(2, 100), throwsRangeError);
       });
- 
+
       test("column may not be outside the line", () {
         expect(() => file.getOffset(1, 20), throwsRangeError);
       });
     });
 
     group("for getText()", () {
       test("end must come after start", () {
         expect(() => file.getText(10, 5), throwsArgumentError);
       });
 
       test("start may not be negative", () {
         expect(() => file.getText(-1, 5), throwsRangeError);
       });
 
       test("end may not be outside the file", () {
         expect(() => file.getText(10, 100), throwsRangeError);
       });
     });
 
     group("for span().union()", () {
       test("source URLs must match", () {
-        var other = new SourceSpan(
-            new SourceLocation(10), new SourceLocation(11), "_");
+        var other =
+            new SourceSpan(new SourceLocation(10), new SourceLocation(11), "_");
 
         expect(() => file.span(9, 10).union(other), throwsArgumentError);
       });
 
       test("spans may not be disjoint", () {
         expect(() => file.span(9, 10).union(file.span(11, 12)),
             throwsArgumentError);
       });
     });
 
@@ skipping 175 matching lines @@
       test("works with an external overlapping span", () {
         var other = file.span(0, 16);
         expect(span.union(other), equals(other));
       });
 
       test("returns a FileSpan for a FileSpan input", () {
         expect(span.union(file.span(0, 5)), new isInstanceOf<FileSpan>());
       });
 
       test("returns a base SourceSpan for a SourceSpan input", () {
-        var other = new SourceSpan(
-            new SourceLocation(0, sourceUrl: "foo.dart"),
-            new SourceLocation(5, sourceUrl: "foo.dart"),
-            "hey, ");
+        var other = new SourceSpan(new SourceLocation(0, sourceUrl: "foo.dart"),
+            new SourceLocation(5, sourceUrl: "foo.dart"), "hey, ");
         var result = span.union(other);
         expect(result, isNot(new isInstanceOf<FileSpan>()));
         expect(result.start, equals(other.start));
         expect(result.end, equals(span.end));
         expect(result.text, equals("hey, ar baz\n"));
       });
     });
 
     group("expand()", () {
       var span;
@@ skipping 37 matching lines @@
         var other = file.span(7, 10);
         expect(span.expand(other), equals(span));
       });
 
       test("works with an external overlapping span", () {
         var other = file.span(0, 16);
         expect(span.expand(other), equals(other));
       });
     });
   });
-}
+}