Issue 23919. Fix for line starts in multiline comments.

pkg/analyzer/test/generated/scanner_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 engine.scanner_test;
 
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/scanner.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:unittest/unittest.dart';
@@ skipping 248 matching lines @@
     scanner.preserveComments = false;
     Token token = scanner.tokenize();
     expect(token, isNotNull);
     expect(token.precedingComments, isNull);
   }
 
   void test_comment_multi() {
     _assertComment(TokenType.MULTI_LINE_COMMENT, "/* comment */");
   }
 
+  void test_comment_multi_lineEnds() {
+    String code = r'''
+/**
+ * aa
+ * bbb
+ * c
+ */''';
+    GatheringErrorListener listener = new GatheringErrorListener();
+    Scanner scanner = new Scanner(null, new CharSequenceReader(code), listener);
+    scanner.tokenize();
+    expect(scanner.lineStarts, equals(<int>[
+      code.indexOf('/**'),
+      code.indexOf(' * aa'),
+      code.indexOf(' * bbb'),
+      code.indexOf(' * c'),
+      code.indexOf(' */')
+    ]));
+  }
+
   void test_comment_multi_unterminated() {
     _assertError(ScannerErrorCode.UNTERMINATED_MULTI_LINE_COMMENT, 3, "/* x");
   }
 
   void test_comment_nested() {
     _assertComment(
         TokenType.MULTI_LINE_COMMENT, "/* comment /* within a */ comment */");
   }
 
   void test_comment_single() {
@@ skipping 1088 matching lines @@
     expect(TokenType.LT_LT.isUserDefinableOperator, isTrue);
     expect(TokenType.MINUS.isUserDefinableOperator, isTrue);
     expect(TokenType.PERCENT.isUserDefinableOperator, isTrue);
     expect(TokenType.PLUS.isUserDefinableOperator, isTrue);
     expect(TokenType.SLASH.isUserDefinableOperator, isTrue);
     expect(TokenType.STAR.isUserDefinableOperator, isTrue);
     expect(TokenType.TILDE.isUserDefinableOperator, isTrue);
     expect(TokenType.TILDE_SLASH.isUserDefinableOperator, isTrue);
   }
 }