Scanner does not properly track line starts for multi-line raw strings

[pq]

Analyzing source:

var a = r'''
blah
''';

b = 1;

yields:

src/scratch.dart 4:1 [syntactic error] Variables must be declared using the keywords 'const', 'final', 'var' or a type name

Net-net the line number should be 5.

I confirmed that making this a non-raw string fixes the line number.

[pq]

To be more precise, here's the actual output:

[error] Variables must be declared using the keywords 'const', 'final', 'var' or a type name (.../lib/src/scratch.dart, line 4, col 1)

[pq]

Related linter issue: #57196

For now I've worked around it but that's not ideal for all the obvious reasons.

[bwilkerson]

I think the following test will catch the problem:

  void test_lineInfo_multilineString_raw() {
    String source = "var a = r'''\nblah\n''';\n\nfoo";
    _assertLineInfo(source, [
      new ScannerTest_ExpectedLocation(0, 1, 1),
      new ScannerTest_ExpectedLocation(14, 2, 2),
      new ScannerTest_ExpectedLocation(source.length - 1, 5, 2)
    ]);
  }

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Added this to the 1.10 milestone.
Removed Priority-Unassigned label.
Added Priority-High label.

[bwilkerson]

Set owner to @bwilkerson.
Added Started label.

[bwilkerson]

https://codereview.chromium.org/1000913004/ (bleeding edge revision 44481)

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Added Fixed label.