Add CommentToken.parent and implement CommentToken.remove().

pkg/front_end/test/scanner_fasta_test.dart

 // Copyright (c) 2017, 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:analyzer/src/fasta/token_utils.dart';
 import 'package:front_end/src/fasta/scanner/error_token.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/keyword.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/string_scanner.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/token.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/token_constants.dart' as fasta;
@@ skipping 118 matching lines @@
       }
 
       token = token.next;
     }
     expect(tokenCount, 26);
     expect(spotCheckCount, 3);
     expect(commentTokenCount, 9);
     expect(token.precedingComments?.lexeme, '// EOF comment');
   }
 
+  void test_CommentToken_remove() {
+    const code = '''
+/// aaa
+/// bbbb
+/// ccccc
+main() {}
+''';
+
+    fasta.Token token;
+    fasta.CommentToken c1;
+    fasta.CommentToken c2;
+    fasta.CommentToken c3;
+
+    void prepareTokens() {
+      token = new fasta.StringScanner(code, includeComments: true).tokenize();
+
+      expect(token.info.kind, fasta.IDENTIFIER_TOKEN);
+
+      c1 = token.precedingCommentTokens;
+      c2 = c1.next;
+      c3 = c2.next;
+      expect(c3.next, isNull);
+
+      expect(c1.parent, token);
+      expect(c2.parent, token);
+      expect(c3.parent, token);
+
+      expect(c1.lexeme, '/// aaa');
+      expect(c2.lexeme, '/// bbbb');
+      expect(c3.lexeme, '/// ccccc');
+    }
+
+    // Remove the first token.
+    {
+      prepareTokens();
+      c1.remove();
+      expect(token.precedingCommentTokens, c2);
+      expect(c2.next, c3);
+      expect(c3.next, isNull);
+    }
+
+    // Remove the second token.
+    {
+      prepareTokens();
+      c2.remove();
+      expect(token.precedingCommentTokens, c1);
+      expect(c1.next, c3);
+      expect(c3.next, isNull);
+    }
+
+    // Remove the last token.
+    {
+      prepareTokens();
+      c3.remove();
+      expect(token.precedingCommentTokens, c1);
+      expect(c1.next, c2);
+      expect(c2.next, isNull);
+    }
+  }
+
+  @override
+  @failingTest
+  void test_incomplete_string_interpolation() {
+    // TODO(danrubel): fix ToAnalyzerTokenStreamConverter_WithListener
+    // to handle synthetic closers in token stream
+    super.test_incomplete_string_interpolation();
+  }
+
   @override
   @failingTest
   void test_mismatched_closer() {
     // TODO(paulberry,ahe): Fasta and analyzer recover this error differently.
     // Figure out which recovery technique we want the front end to use.
     super.test_mismatched_closer();
   }
 
   @override
   @failingTest
   void test_mismatched_opener() {
     // TODO(paulberry,ahe): Fasta and analyzer recover this error differently.
     // Figure out which recovery technique we want the front end to use.
     super.test_mismatched_opener();
   }
 
-  void test_next_previous() {
-    const source = 'int a; /*1*/ /*2*/ /*3*/ B f(){if (a < 2) {}}';
-    fasta.Token token =
-        new fasta.StringScanner(source, includeComments: true).tokenize();
-    while (!token.isEof) {
-      expect(token.next.previousToken, token);
-      fasta.CommentToken commentToken = token.precedingComments;
-      while (commentToken != null) {
-        if (commentToken.next != null) {
-          expect(commentToken.next.previousToken, commentToken);
-        }
-        commentToken = commentToken.next;
-      }
-      token = token.next;
-    }
-  }
-
-  @override
-  @failingTest
-  void test_incomplete_string_interpolation() {
-    // TODO(danrubel): fix ToAnalyzerTokenStreamConverter_WithListener
-    // to handle synthetic closers in token stream
-    super.test_incomplete_string_interpolation();
-  }
-
   @override
   void test_mismatched_opener_in_interpolation() {
     // When openers and closers are mismatched,
     // fasta favors considering the opener to be mismatched
     // and inserts synthetic closers as needed.
     // r'"${({(}}"' is parsed as r'"${({()})}"'
     // where both ')' are synthetic
     var stringStart = _scan(r'"${({(}}"');
     var interpolationStart = stringStart.next as BeginToken;
     var openParen1 = interpolationStart.next as BeginToken;
     var openBrace = openParen1.next as BeginToken;
     var openParen2 = openBrace.next as BeginToken;
     var closeParen2 = openParen2.next;
     var closeBrace = closeParen2.next;
     var closeParen1 = closeBrace.next;
     var interpolationEnd = closeParen1.next;
     var stringEnd = interpolationEnd.next;
     expect(stringEnd.next.type, TokenType.EOF);
     expect(interpolationStart.endToken, same(interpolationEnd));
     expect(openParen1.endToken, same(closeParen1));
     expect(openBrace.endToken, same(closeBrace));
     expect(openParen2.endToken, same(closeParen2));
   }
 
+  void test_next_previous() {
+    const source = 'int a; /*1*/ /*2*/ /*3*/ B f(){if (a < 2) {}}';
+    fasta.Token token =
+        new fasta.StringScanner(source, includeComments: true).tokenize();
+    while (!token.isEof) {
+      expect(token.next.previousToken, token);
+      fasta.CommentToken commentToken = token.precedingComments;
+      while (commentToken != null) {
+        if (commentToken.next != null) {
+          expect(commentToken.next.previousToken, commentToken);
+        }
+        commentToken = commentToken.next;
+      }
+      token = token.next;
+    }
+  }
+
   @override
   @failingTest
   void test_string_multi_unterminated() {
     // TODO(paulberry,ahe): bad error recovery.
     super.test_string_multi_unterminated();
   }
 
   @override
   @failingTest
   void test_string_multi_unterminated_interpolation_block() {
@@ skipping 283 matching lines @@
   final ErrorListener _listener;
 
   ToAnalyzerTokenStreamConverter_WithListener(this._listener);
 
   @override
   void reportError(
       ScannerErrorCode errorCode, int offset, List<Object> arguments) {
     _listener.errors.add(new TestError(offset, errorCode, arguments));
   }
 }