Add LineScanner and SpanScanner classes to string_scanner.

pkg/string_scanner/test/expect_error_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.
-
-library string_scanner.expect_error_test;
-
-import 'package:string_scanner/string_scanner.dart';
-import 'package:unittest/unittest.dart';
-
-import 'utils.dart';
-
-void main() {
-  test('points to the first unconsumed character', () {
-    var scanner = new StringScanner('foo bar baz');
-    scanner.expect('foo ');
-    expect(() => scanner.expect('foo'), throwsFormattedError('''
-Error on line 1, column 5: expected "foo".
-foo bar baz
-    ^'''));
-  });
-
-  test('prints the correct line', () {
-    var scanner = new StringScanner('foo bar baz\ndo re mi\nearth fire water');
-    scanner.expect('foo bar baz\ndo ');
-    expect(() => scanner.expect('foo'), throwsFormattedError('''
-Error on line 2, column 4: expected "foo".
-do re mi
-   ^'''));
-  });
-
-  test('handles the beginning of the string correctly', () {
-    var scanner = new StringScanner('foo bar baz');
-    expect(() => scanner.expect('zap'), throwsFormattedError('''
-Error on line 1, column 1: expected "zap".
-foo bar baz
-^'''));
-  });
-
-  test('handles the end of the string correctly', () {
-    var scanner = new StringScanner('foo bar baz');
-    scanner.expect('foo bar baz');
-    expect(() => scanner.expect('bang'), throwsFormattedError('''
-Error on line 1, column 12: expected "bang".
-foo bar baz
-           ^'''));
-  });
-
-  test('handles an empty string correctly', () {
-    expect(() => new StringScanner('').expect('foo'), throwsFormattedError('''
-Error on line 1, column 1: expected "foo".
-
-^'''));
-  });
-
-  group("expected name", () {
-    test("uses the provided name", () {
-      expect(() => new StringScanner('').expect('foo bar', name: 'zap'),
-          throwsFormattedError('''
-Error on line 1, column 1: expected zap.
-
-^'''));
-    });
-
-    test("escapes string quotes", () {
-      expect(() => new StringScanner('').expect('foo"bar'),
-          throwsFormattedError('''
-Error on line 1, column 1: expected "foo\\"bar".
-
-^'''));
-    });
-
-    test("escapes string backslashes", () {
-      expect(() => new StringScanner('').expect('foo\\bar'),
-          throwsFormattedError('''
-Error on line 1, column 1: expected "foo\\\\bar".
-
-^'''));
-    });
-
-    test("prints PERL-style regexps", () {
-      expect(() => new StringScanner('').expect(new RegExp(r'foo')),
-          throwsFormattedError('''
-Error on line 1, column 1: expected /foo/.
-
-^'''));
-    });
-
-    test("escape regexp forward slashes", () {
-      expect(() => new StringScanner('').expect(new RegExp(r'foo/bar')),
-          throwsFormattedError('''
-Error on line 1, column 1: expected /foo\\/bar/.
-
-^'''));
-    });
-
-    test("does not escape regexp backslashes", () {
-      expect(() => new StringScanner('').expect(new RegExp(r'foo\bar')),
-          throwsFormattedError('''
-Error on line 1, column 1: expected /foo\\bar/.
-
-^'''));
-    });
-  });
-}