Support multiple occurrences of text in context

test/span_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';
 import 'package:source_span/src/colors.dart' as colors;
 
 main() {
   var span;
@@ skipping 47 matching lines @@
               start, end, "abc", "\n--abc--"), throwsArgumentError);
         expect(() => new SourceSpanWithContext(
               start, end, "abc", "\n----abc--"), throwsArgumentError);
         expect(() => new SourceSpanWithContext(
               start, end, "abc", "\n\n--abc--"), throwsArgumentError);
 
         // However, these are valid:
         new SourceSpanWithContext(start, end, "abc", "\n---abc--");
         new SourceSpanWithContext(start, end, "abc", "\n\n---abc--");
       });
+
+      test('text can occur multiple times in context', () {
+        var start1 = new SourceLocation(4, line: 55, column: 2);
+        var end1 = new SourceLocation(7, line: 55, column: 5);
+        var start2 = new SourceLocation(4, line: 55, column: 8);
+        var end2 = new SourceLocation(7, line: 55, column: 11);
+        new SourceSpanWithContext(start1, end1, "abc", "--abc---abc--\n");
+        new SourceSpanWithContext(start1, end1, "abc", "--abc--abc--\n");
+        new SourceSpanWithContext(start2, end2, "abc", "--abc---abc--\n");
+        new SourceSpanWithContext(start2, end2, "abc", "---abc--abc--\n");
+        expect(() => new SourceSpanWithContext(
+              start1, end1, "abc", "---abc--abc--\n"), throwsArgumentError);
+        expect(() => new SourceSpanWithContext(
+              start2, end2, "abc", "--abc--abc--\n"), throwsArgumentError);
+      });
     });
 
     group('for union()', () {
       test('source URLs must match', () {
         var other = new SourceSpan(
             new SourceLocation(12, sourceUrl: "bar.dart"),
             new SourceLocation(13, sourceUrl: "bar.dart"),
             "_");
 
         expect(() => span.union(other), throwsArgumentError);
@@ skipping 233 matching lines @@
     test("a different source URL isn't equal", () {
       var other = new SourceSpan(
           new SourceLocation(5, sourceUrl: "bar.dart"),
           new SourceLocation(12, sourceUrl: "bar.dart"),
           "foo bar");
 
       expect(span, isNot(equals(other)));
     });
   });
 }