[analyzer] Add an API to get a language comment token off a unit.

Change-Id: I377fdc44d5e514d6d9a601b3947c3908e5a4497a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/140768
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>

pkg/_fe_analyzer_shared/lib/src/scanner/token.dart

@@ -460,6 +460,29 @@ class KeywordToken extends SimpleToken {
   Object value() => keyword;
 }
 
+/**
+ * A specialized comment token representing a language version
+ * (e.g. '// @dart = 2.1').
+ */
+class LanguageVersionToken extends CommentToken {
+  /**
+   * The major language version.
+   */
+  final int major;
+
+  /**
+   * The minor language version.
+   */
+  final int minor;
+
+  LanguageVersionToken.from(String text, int offset, this.major, this.minor)
+      : super(TokenType.SINGLE_LINE_COMMENT, text, offset);
+
+  @override
+  LanguageVersionToken copy() =>
+      new LanguageVersionToken.from(lexeme, offset, major, minor);
+}
+
 /**
  * A token that was scanned from the input. Each token knows which tokens
  * precede and follow it, acting as a link in a doubly linked list of tokens.

pkg/_fe_analyzer_shared/lib/src/scanner/token_impl.dart

@@ -187,19 +187,12 @@ class CommentToken extends StringToken implements analyzer.CommentToken {
   }
 }
 
-/**
- * A specialized comment token representing a language version
- * (e.g. '// @dart = 2.1').
- */
-class LanguageVersionToken extends CommentToken {
-  /**
-   * The major language version.
-   */
+class LanguageVersionToken extends CommentToken
+    implements analyzer.LanguageVersionToken {
+  @override
   int major;
 
-  /**
-   * The minor language version.
-   */
+  @override
   int minor;
 
   LanguageVersionToken.from(String text, int offset, this.major, this.minor)

pkg/analysis_server/test/integration/linter/lint_names_test.dart

@@ -76,7 +76,6 @@ class CompilationUnitParser {
     var parser = Parser(
       stringSource,
       errorListener,
-      languageVersion: scanner.languageVersion,
       featureSet: featureSet,
     );
     var cu = parser.parseCompilationUnit(startToken);

pkg/analyzer/lib/analyzer.dart

@@ -127,7 +127,6 @@ CompilationUnit parseDirectives(String contents,
   var parser = Parser(
     source,
     errorCollector,
-    languageVersion: scanner.languageVersion,
     featureSet: featureSet,
   );
   var unit = parser.parseDirectives(token);
@@ -155,7 +154,6 @@ CompilationUnit _parseSource(
   var parser = Parser(
     source,
     errorCollector,
-    languageVersion: scanner.languageVersion,
     featureSet: featureSet,
   )..parseFunctionBodies = parseFunctionBodies;
   var unit = parser.parseCompilationUnit(token)

pkg/analyzer/lib/dart/analysis/utilities.dart

@@ -121,7 +121,6 @@ ParseStringResult parseString(
   var parser = Parser(
     source,
     errorCollector,
-    languageVersion: scanner.languageVersion,
     featureSet: scanner.featureSet,
   );
   var unit = parser.parseCompilationUnit(token);

pkg/analyzer/lib/dart/ast/ast.dart

@@ -1237,9 +1237,12 @@ abstract class CompilationUnit implements AstNode {
   /// resynthesized from a summary.
   FeatureSet get featureSet;
 
+  @Deprecated("Use languageVersionToken")
+  LanguageVersion get languageVersion;
+
   /// The language version override specified for this compilation unit using a
   /// token like '// @dart = 2.7', or `null` if no override is specified.
-  LanguageVersion get languageVersion;
+  LanguageVersionToken get languageVersionToken;
 
   /// Return the line information for this compilation unit.
   LineInfo get lineInfo;

pkg/analyzer/lib/dart/ast/ast_factory.dart

@@ -5,7 +5,6 @@
 import 'package:_fe_analyzer_shared/src/scanner/token.dart';
 import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/dart/ast/language_version.dart';
 import 'package:analyzer/src/generated/utilities_dart.dart';
 import 'package:meta/meta.dart';
 
@@ -166,8 +165,7 @@ abstract class AstFactory {
       List<Directive> directives,
       List<CompilationUnitMember> declarations,
       @required Token endToken,
-      @required FeatureSet featureSet,
-      LanguageVersion languageVersion});
+      @required FeatureSet featureSet});
 
   /// Returns a newly created conditional expression.
   ConditionalExpression conditionalExpression(

pkg/analyzer/lib/dart/ast/language_version.dart

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 /// The language version override specified for a compilation unit.
+@Deprecated("Use unit.languageVersionToken instead")
 class LanguageVersion {
   final int major;
   final int minor;

pkg/analyzer/lib/dart/ast/token.dart

@@ -5,4 +5,4 @@
 /// Defines the tokens that are produced by the scanner, used by the parser, and
 /// referenced from the [AST structure](ast.dart).
 export 'package:_fe_analyzer_shared/src/scanner/token.dart'
-    show Keyword, Token, TokenType;
+    show Keyword, Token, TokenType, LanguageVersionToken;

pkg/analyzer/lib/src/dart/analysis/file_state.dart

@@ -536,7 +536,6 @@ class FileState {
     return astFactory.compilationUnit(
       beginToken: token,
       endToken: token,
-      languageVersion: null,
       featureSet: _featureSet,
     )..lineInfo = LineInfo(const <int>[0]);
   }
@@ -599,7 +598,6 @@ class FileState {
     Parser parser = Parser(
       source,
       errorListener,
-      languageVersion: scanner.languageVersion,
       featureSet: scanner.featureSet,
       useFasta: useFasta,
     );

pkg/analyzer/lib/src/dart/ast/ast.dart

@@ -2026,7 +2026,22 @@ class CompilationUnitImpl extends AstNodeImpl implements CompilationUnit {
   LineInfo lineInfo;
 
   @override
-  final LanguageVersion languageVersion;
+  LanguageVersion get languageVersion {
+    final token = languageVersionToken;
+    return LanguageVersion(token.major, token.minor);
+  }
+
+  @override
+  LanguageVersionToken get languageVersionToken {
+    CommentToken comment = beginToken.precedingComments;
+    while (comment != null) {
+      if (comment is LanguageVersionToken) {
+        return comment;
+      }
+      comment = comment.next;
+    }
+    return null;
+  }
 
   @override
   final FeatureSet featureSet;
@@ -2042,7 +2057,6 @@ class CompilationUnitImpl extends AstNodeImpl implements CompilationUnit {
       List<Directive> directives,
       List<CompilationUnitMember> declarations,
       this.endToken,
-      this.languageVersion,
       this.featureSet) {
     _scriptTag = _becomeParentOf(scriptTag);
     _directives = NodeListImpl<Directive>(this, directives);

pkg/analyzer/lib/src/dart/ast/ast_factory.dart

@@ -6,7 +6,6 @@ import 'package:_fe_analyzer_shared/src/scanner/token.dart';
 import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/ast_factory.dart';
-import 'package:analyzer/dart/ast/language_version.dart';
 import 'package:analyzer/src/dart/ast/ast.dart';
 import 'package:analyzer/src/generated/utilities_dart.dart';
 import 'package:meta/meta.dart';
@@ -186,10 +185,9 @@ class AstFactoryImpl extends AstFactory {
           List<Directive> directives,
           List<CompilationUnitMember> declarations,
           Token endToken,
-          FeatureSet featureSet,
-          LanguageVersion languageVersion}) =>
+          FeatureSet featureSet}) =>
       CompilationUnitImpl(beginToken, scriptTag, directives, declarations,
-          endToken, languageVersion, featureSet);
+          endToken, featureSet);
 
   @override
   ConditionalExpression conditionalExpression(

pkg/analyzer/lib/src/dart/ast/utilities.dart

@@ -286,7 +286,6 @@ class AstCloner implements AstVisitor<AstNode> {
         directives: cloneNodeList(node.directives),
         declarations: cloneNodeList(node.declarations),
         endToken: cloneToken(node.endToken),
-        languageVersion: node.languageVersion,
         featureSet: node.featureSet);
     clone.lineInfo = node.lineInfo;
     return clone;

pkg/analyzer/lib/src/dart/micro/library_graph.dart

@@ -108,7 +108,6 @@ class FileState {
     Parser parser = Parser(
       source,
       errorListener,
-      languageVersion: scanner.languageVersion,
       featureSet: scanner.featureSet,
       useFasta: useFasta,
     );

pkg/analyzer/lib/src/dart/scanner/scanner.dart

@@ -8,7 +8,6 @@ import 'package:_fe_analyzer_shared/src/scanner/scanner.dart' as fasta;
 import 'package:_fe_analyzer_shared/src/scanner/token.dart'
     show Token, TokenType;
 import 'package:analyzer/dart/analysis/features.dart';
-import 'package:analyzer/dart/ast/language_version.dart';
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/error/listener.dart';
 import 'package:analyzer/src/dart/error/syntactic_errors.dart';
@@ -72,7 +71,7 @@ class Scanner {
    */
   bool enableNonNullable = false;
 
-  LanguageVersion _languageVersion;
+  fasta.LanguageVersionToken _languageVersion;
 
   FeatureSet _featureSet;
 
@@ -114,7 +113,7 @@ class Scanner {
    * The language version override specified for this compilation unit using a
    * token like '// @dart = 2.7', or `null` if no override is specified.
    */
-  LanguageVersion get languageVersion => _languageVersion;
+  fasta.LanguageVersionToken get languageVersion => _languageVersion;
 
   set preserveComments(bool preserveComments) {
     this._preserveComments = preserveComments;
@@ -199,10 +198,7 @@ class Scanner {
   void _languageVersionChanged(
       fasta.Scanner scanner, fasta.LanguageVersionToken languageVersion) {
     if (languageVersion.major >= 0 && languageVersion.minor >= 0) {
-      _languageVersion = LanguageVersion(
-        languageVersion.major,
-        languageVersion.minor,
-      );
+      _languageVersion = languageVersion;
       if (_featureSet != null) {
         _featureSet = _featureSet.restrictToVersion(
             Version(languageVersion.major, languageVersion.minor, 0));

pkg/analyzer/lib/src/fasta/ast_builder.dart

@@ -50,7 +50,6 @@ import 'package:_fe_analyzer_shared/src/scanner/token_constants.dart';
 import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/ast_factory.dart' show AstFactory;
-import 'package:analyzer/dart/ast/language_version.dart';
 import 'package:analyzer/dart/ast/standard_ast_factory.dart' as standard;
 import 'package:analyzer/dart/ast/token.dart' show Token, TokenType;
 import 'package:analyzer/error/listener.dart';
@@ -127,13 +126,10 @@ class AstBuilder extends StackListener {
   /// `true` if variance behavior is enabled
   final bool enableVariance;
 
-  /// The language version override, `null` if not such token.
-  LanguageVersion _languageVersion;
-
   final FeatureSet _featureSet;
 
   AstBuilder(ErrorReporter errorReporter, this.fileUri, this.isFullAst,
-      this._languageVersion, this._featureSet,
+      this._featureSet,
       [Uri uri])
       : this.errorReporter = FastaErrorReporter(errorReporter),
         this.enableNonNullable = _featureSet.isEnabled(Feature.non_nullable),
@@ -959,7 +955,6 @@ class AstBuilder extends StackListener {
         directives: directives,
         declarations: declarations,
         endToken: endToken,
-        languageVersion: _languageVersion,
         featureSet: _featureSet) as CompilationUnitImpl;
     push(unit);
   }

pkg/analyzer/lib/src/generated/parser.dart

@@ -15,7 +15,6 @@ import 'package:_fe_analyzer_shared/src/parser/type_info.dart' as fasta;
 import 'package:_fe_analyzer_shared/src/scanner/scanner.dart' as fasta;
 import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/dart/ast/language_version.dart';
 import 'package:analyzer/dart/ast/standard_ast_factory.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/error/error.dart';
@@ -202,12 +201,10 @@ class Parser {
   /// Initialize a newly created parser to parse tokens in the given [_source]
   /// and to report any errors that are found to the given [_errorListener].
   factory Parser(Source source, AnalysisErrorListener errorListener,
-      {bool useFasta,
-      LanguageVersion languageVersion,
-      @required FeatureSet featureSet}) {
+      {bool useFasta, @required FeatureSet featureSet}) {
     featureSet ??= FeatureSet.fromEnableFlags([]);
     if (useFasta ?? Parser.useFasta) {
-      return _Parser2(source, errorListener, languageVersion, featureSet,
+      return _Parser2(source, errorListener, featureSet,
           allowNativeClause: true);
     } else {
       return Parser.withoutFasta(source, errorListener, featureSet: featureSet);
@@ -1904,7 +1901,6 @@ class Parser {
           return astFactory.compilationUnit(
             beginToken: eof,
             endToken: eof,
-            languageVersion: null,
             featureSet: _featureSet,
           );
         }
@@ -1961,7 +1957,6 @@ class Parser {
       directives: directives,
       declarations: declarations,
       endToken: _currentToken,
-      languageVersion: null,
       featureSet: _featureSet,
     );
   }
@@ -2418,7 +2413,6 @@ class Parser {
           scriptTag: scriptTag,
           directives: directives,
           endToken: _currentToken,
-          languageVersion: null,
           featureSet: _featureSet,
         );
       }
@@ -2428,7 +2422,6 @@ class Parser {
       scriptTag: scriptTag,
       directives: directives,
       endToken: _currentToken,
-      languageVersion: null,
       featureSet: _featureSet,
     );
   }

pkg/analyzer/lib/src/generated/parser_fasta.dart

@@ -24,11 +24,10 @@ abstract class ParserAdapter implements Parser {
   final AstBuilder astBuilder;
 
   ParserAdapter(this.currentToken, ErrorReporter errorReporter, Uri fileUri,
-      LanguageVersion languageVersion, FeatureSet featureSet,
+      FeatureSet featureSet,
       {bool allowNativeClause = false})
       : fastaParser = fasta.Parser(null),
-        astBuilder = AstBuilder(
-            errorReporter, fileUri, true, languageVersion, featureSet) {
+        astBuilder = AstBuilder(errorReporter, fileUri, true, featureSet) {
     fastaParser.listener = astBuilder;
     astBuilder.parser = fastaParser;
     astBuilder.allowNativeClause = allowNativeClause;
@@ -379,23 +378,21 @@ class _Parser2 extends ParserAdapter {
   @override
   bool enableUriInPartOf = true;
 
-  factory _Parser2(Source source, AnalysisErrorListener errorListener,
-      LanguageVersion languageVersion, FeatureSet featureSet,
+  factory _Parser2(
+      Source source, AnalysisErrorListener errorListener, FeatureSet featureSet,
       {bool allowNativeClause = false}) {
     var errorReporter = ErrorReporter(
       errorListener,
       source,
       isNonNullableByDefault: featureSet.isEnabled(Feature.non_nullable),
     );
-    return _Parser2._(
-        source, errorReporter, source.uri, languageVersion, featureSet,
+    return _Parser2._(source, errorReporter, source.uri, featureSet,
         allowNativeClause: allowNativeClause);
   }
 
   _Parser2._(this._source, ErrorReporter errorReporter, Uri fileUri,
-      LanguageVersion languageVersion, FeatureSet featureSet,
-      {bool allowNativeClause = false})
-      : super(null, errorReporter, fileUri, languageVersion, featureSet,
+      FeatureSet featureSet, {bool allowNativeClause = false})
+      : super(null, errorReporter, fileUri, featureSet,
             allowNativeClause: allowNativeClause);
 
   @override

pkg/analyzer/lib/src/generated/testing/ast_test_factory.dart

@@ -4,7 +4,6 @@
 
 import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/dart/ast/language_version.dart';
 import 'package:analyzer/dart/ast/standard_ast_factory.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/element/element.dart';
@@ -293,14 +292,12 @@ class AstTestFactory {
           directives: directives ?? <Directive>[],
           declarations: declarations ?? <CompilationUnitMember>[],
           endToken: TokenFactory.tokenFromType(TokenType.EOF),
-          languageVersion: null,
           featureSet: null);
 
   static CompilationUnit compilationUnit9(
           {String scriptTag,
           List<Directive> directives,
           List<CompilationUnitMember> declarations,
-          LanguageVersion languageVersion,
           FeatureSet featureSet}) =>
       astFactory.compilationUnit(
           beginToken: TokenFactory.tokenFromType(TokenType.EOF),
@@ -309,7 +306,6 @@ class AstTestFactory {
           directives: directives ?? <Directive>[],
           declarations: declarations ?? <CompilationUnitMember>[],
           endToken: TokenFactory.tokenFromType(TokenType.EOF),
-          languageVersion: languageVersion,
           featureSet: featureSet);
 
   static ConditionalExpression conditionalExpression(Expression condition,

pkg/analyzer/lib/src/summary2/ast_binary_reader.dart

@@ -358,7 +358,6 @@ class AstBinaryReader {
         directives: _readNodeList(data.compilationUnit_directives),
         declarations: _readNodeList(data.compilationUnit_declarations),
         endToken: null,
-        languageVersion: null,
         featureSet: null);
   }
 

pkg/analyzer/test/dart/analysis/utilities_test.dart

@@ -214,7 +214,7 @@ class A {}
       featureSet: FeatureSet.fromEnableFlags([]),
     );
 
-    var languageVersion = result.unit.languageVersion;
+    var languageVersion = result.unit.languageVersionToken;
     expect(languageVersion.major, 2);
     expect(languageVersion.minor, 7);
   }
@@ -229,7 +229,7 @@ class A {}
       featureSet: FeatureSet.fromEnableFlags([]),
     );
 
-    expect(result.unit.languageVersion, isNull);
+    expect(result.unit.languageVersionToken, isNull);
   }
 
   test_parseString_lineInfo() {

pkg/analyzer/test/dart/ast/ast_test.dart

@@ -741,7 +741,6 @@ E f() => g;
       _unit = Parser(
         source,
         listener,
-        languageVersion: scanner.languageVersion,
         featureSet: featureSet,
         useFasta: true,
       ).parseCompilationUnit(tokens);

pkg/analyzer/test/generated/parser_fasta_test.dart

@@ -10,12 +10,12 @@ import 'package:_fe_analyzer_shared/src/scanner/error_token.dart'
     show ErrorToken;
 import 'package:_fe_analyzer_shared/src/scanner/scanner.dart' as fasta;
 import 'package:_fe_analyzer_shared/src/scanner/scanner.dart'
-    show LanguageVersionToken, ScannerConfiguration, ScannerResult, scanString;
+    show ScannerConfiguration, ScannerResult, scanString;
 import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/dart/ast/language_version.dart';
 import 'package:analyzer/dart/ast/token.dart' as analyzer;
-import 'package:analyzer/dart/ast/token.dart' show Token, TokenType;
+import 'package:analyzer/dart/ast/token.dart'
+    show Token, TokenType, LanguageVersionToken;
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/error/listener.dart' show ErrorReporter;
 import 'package:analyzer/src/dart/ast/ast.dart';
@@ -1962,9 +1962,7 @@ class FastaParserTestCase
 
   @override
   void createParser(String content,
-      {int expectedEndOffset,
-      LanguageVersion languageVersion,
-      FeatureSet featureSet}) {
+      {int expectedEndOffset, FeatureSet featureSet}) {
     featureSet ??= FeatureSet.forTesting();
     var result = scanString(content,
         configuration: featureSet.isEnabled(Feature.non_nullable)
@@ -1972,7 +1970,7 @@ class FastaParserTestCase
             : ScannerConfiguration.classic,
         includeComments: true);
     _fastaTokens = result.tokens;
-    _parserProxy = ParserProxy(_fastaTokens, languageVersion, featureSet,
+    _parserProxy = ParserProxy(_fastaTokens, featureSet,
         allowNativeClause: allowNativeClause,
         expectedEndOffset: expectedEndOffset);
   }
@@ -2083,7 +2081,7 @@ class FastaParserTestCase
 
   CompilationUnit parseCompilationUnit2(
       String content, GatheringErrorListener listener,
-      {LanguageVersion languageVersion, FeatureSet featureSet}) {
+      {LanguageVersionToken languageVersion, FeatureSet featureSet}) {
     featureSet ??= FeatureSet.forTesting();
     var source = StringSource(content, 'parser_test_StringSource.dart');
 
@@ -2109,8 +2107,8 @@ class FastaParserTestCase
       isNonNullableByDefault: false,
     );
     fasta.Parser parser = fasta.Parser(null);
-    AstBuilder astBuilder = AstBuilder(
-        errorReporter, source.uri, true, languageVersion, featureSet);
+    AstBuilder astBuilder =
+        AstBuilder(errorReporter, source.uri, true, featureSet);
     parser.listener = astBuilder;
     astBuilder.parser = parser;
     astBuilder.allowNativeClause = allowNativeClause;
@@ -3520,8 +3518,7 @@ class ParserProxy extends analyzer.ParserAdapter {
    * Creates a [ParserProxy] which is prepared to begin parsing at the given
    * Fasta token.
    */
-  factory ParserProxy(analyzer.Token firstToken,
-      LanguageVersion languageVersion, FeatureSet featureSet,
+  factory ParserProxy(analyzer.Token firstToken, FeatureSet featureSet,
       {bool allowNativeClause = false, int expectedEndOffset}) {
     TestSource source = TestSource();
     var errorListener = GatheringErrorListener(checkRanges: true);
@@ -3530,22 +3527,16 @@ class ParserProxy extends analyzer.ParserAdapter {
       source,
       isNonNullableByDefault: false,
     );
-    return ParserProxy._(firstToken, errorReporter, null, errorListener,
-        languageVersion, featureSet,
+    return ParserProxy._(
+        firstToken, errorReporter, null, errorListener, featureSet,
         allowNativeClause: allowNativeClause,
         expectedEndOffset: expectedEndOffset);
   }
 
-  ParserProxy._(
-      analyzer.Token firstToken,
-      ErrorReporter errorReporter,
-      Uri fileUri,
-      this._errorListener,
-      LanguageVersion languageVersion,
-      FeatureSet featureSet,
-      {bool allowNativeClause = false,
-      this.expectedEndOffset})
-      : super(firstToken, errorReporter, fileUri, languageVersion, featureSet,
+  ParserProxy._(analyzer.Token firstToken, ErrorReporter errorReporter,
+      Uri fileUri, this._errorListener, FeatureSet featureSet,
+      {bool allowNativeClause = false, this.expectedEndOffset})
+      : super(firstToken, errorReporter, fileUri, featureSet,
             allowNativeClause: allowNativeClause) {
     _eventListener = ForwardingTestListener(astBuilder);
     fastaParser.listener = _eventListener;

pkg/analyzer/test/generated/parser_test.dart

@@ -9,7 +9,6 @@ import 'package:_fe_analyzer_shared/src/scanner/scanner.dart'
     show ScannerResult, scanString;
 import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/dart/ast/language_version.dart';
 import 'package:analyzer/dart/ast/standard_ast_factory.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
@@ -115,7 +114,6 @@ abstract class AbstractParserTestCase implements ParserTestHelpers {
   void createParser(
     String content, {
     int expectedEndOffset,
-    LanguageVersion languageVersion,
     FeatureSet featureSet,
   });
 
@@ -9476,7 +9474,7 @@ class ParserTestCase with ParserTestHelpers implements AbstractParserTestCase {
   void createParser(
     String content, {
     int expectedEndOffset,
-    LanguageVersion languageVersion,
+    LanguageVersionToken languageVersion,
     FeatureSet featureSet,
   }) {
     Source source = TestSource();
@@ -9488,7 +9486,6 @@ class ParserTestCase with ParserTestHelpers implements AbstractParserTestCase {
     parser = Parser(
       source,
       listener,
-      languageVersion: languageVersion,
       featureSet: featureSet,
     );
     parser.allowNativeClause = allowNativeClause;
@@ -9623,7 +9620,6 @@ class ParserTestCase with ParserTestHelpers implements AbstractParserTestCase {
     Parser parser = Parser(
       source,
       listener,
-      languageVersion: null,
       featureSet: FeatureSet.forTesting(),
     );
     parser.enableOptionalNewAndConst = enableOptionalNewAndConst;
@@ -9652,7 +9648,6 @@ class ParserTestCase with ParserTestHelpers implements AbstractParserTestCase {
     Parser parser = Parser(
       source,
       listener,
-      languageVersion: null,
       featureSet: FeatureSet.forTesting(),
     );
     parser.enableOptionalNewAndConst = enableOptionalNewAndConst;
@@ -9993,7 +9988,6 @@ class ParserTestCase with ParserTestHelpers implements AbstractParserTestCase {
     Parser parser = Parser(
       source,
       listener,
-      languageVersion: null,
       featureSet: FeatureSet.forTesting(),
     );
     parser.enableOptionalNewAndConst = enableOptionalNewAndConst;
@@ -10024,7 +10018,6 @@ class ParserTestCase with ParserTestHelpers implements AbstractParserTestCase {
     Parser parser = Parser(
       source,
       listener,
-      languageVersion: null,
       featureSet: FeatureSet.forTesting(),
     );
     parser.enableOptionalNewAndConst = enableOptionalNewAndConst;
@@ -12425,7 +12418,6 @@ class SimpleParserTest extends ParserTestCase with SimpleParserTestMixin {
       Parser(
         NonExistingSource.unknown,
         null,
-        languageVersion: null,
         featureSet: FeatureSet.forTesting(),
       ),
       isNotNull,

pkg/analyzer/test/generated/utilities_test.dart

@@ -1187,7 +1187,6 @@ library l;''');
     Parser parser = Parser(
       NonExistingSource.unknown,
       listener,
-      languageVersion: scanner.languageVersion,
       featureSet: featureSet,
     );
     CompilationUnit unit = parser.parseCompilationUnit(token);

pkg/analyzer/test/src/dart/analysis/driver_test.dart

@@ -1620,7 +1620,7 @@ class A{}
 ''');
 
     var result = await driver.getResult(path);
-    var languageVersion = result.unit.languageVersion;
+    var languageVersion = result.unit.languageVersionToken;
     expect(languageVersion.major, 2);
     expect(languageVersion.minor, 7);
   }
@@ -2208,7 +2208,7 @@ class A {}
 ''');
 
     var parseResult = driver.parseFileSync(path);
-    var languageVersion = parseResult.unit.languageVersion;
+    var languageVersion = parseResult.unit.languageVersionToken;
     expect(languageVersion.major, 2);
     expect(languageVersion.minor, 7);
   }
@@ -2221,7 +2221,7 @@ class A {}
 ''');
 
     var parseResult = driver.parseFileSync(path);
-    expect(parseResult.unit.languageVersion, isNull);
+    expect(parseResult.unit.languageVersionToken, isNull);
   }
 
   test_parseFileSync_notAbsolutePath() async {

pkg/analyzer/test/src/dart/ast/ast_test.dart

@@ -14,12 +14,69 @@ import '../../../generated/resolver_test_case.dart';
 
 main() {
   defineReflectiveSuite(() {
+    defineReflectiveTests(CompilationUnitImplTest);
     defineReflectiveTests(ExpressionImplTest);
     defineReflectiveTests(InstanceCreationExpressionImplTest);
     defineReflectiveTests(IntegerLiteralImplTest);
   });
 }
 
+@reflectiveTest
+class CompilationUnitImplTest extends ParserTestCase {
+  String testSource;
+  CompilationUnitImpl testUnit;
+
+  void parse(String source) {
+    testSource = source;
+    testUnit = parseCompilationUnit(source);
+  }
+
+  test_languageVersionComment_none() {
+    parse('''
+void main() {}
+''');
+    expect(testUnit.languageVersionToken, null);
+  }
+
+  test_languageVersionComment_none_onlyNormalComment() {
+    parse('''
+// A normal comment.
+void main() {}
+''');
+    expect(testUnit.languageVersionToken, null);
+  }
+
+  test_languageVersionComment_firstComment() {
+    parse('''
+// @dart=2.6
+void main() {}
+''');
+    expect(
+        testUnit.languageVersionToken, testUnit.beginToken.precedingComments);
+  }
+
+  test_languageVersionComment_secondComment() {
+    parse('''
+// A normal comment.
+// @dart=2.6
+void main() {}
+''');
+    expect(testUnit.languageVersionToken,
+        testUnit.beginToken.precedingComments.next);
+  }
+
+  test_languageVersionComment_thirdComment() {
+    parse('''
+// A normal comment.
+// Another normal comment.
+// @dart=2.6
+void main() {}
+''');
+    expect(testUnit.languageVersionToken,
+        testUnit.beginToken.precedingComments.next.next);
+  }
+}
+
 @reflectiveTest
 class ExpressionImplTest extends ParserTestCase {
   String testSource;

pkg/analyzer/test/src/dart/ast/parse_base.dart

@@ -37,7 +37,6 @@ class ParseBase with ResourceProviderMixin {
     var parser = Parser(
       source,
       errorListener,
-      languageVersion: scanner.languageVersion,
       featureSet: featureSet,
       useFasta: useFasta,
     );

pkg/analyzer/test/src/summary/test_strategies.dart

@@ -31,7 +31,6 @@ CompilationUnit parseText(
   Parser parser = Parser(
     NonExistingSource.unknown,
     AnalysisErrorListener.NULL_LISTENER,
-    languageVersion: scanner.languageVersion,
     featureSet: scanner.featureSet,
   );
   CompilationUnit unit = parser.parseCompilationUnit(token);

pkg/analyzer_cli/tool/perf.dart

@@ -86,7 +86,6 @@ CompilationUnit parseDirectives(Source source) {
   var parser = Parser(
     source,
     AnalysisErrorListener.NULL_LISTENER,
-    languageVersion: null,
     featureSet: FeatureSet.fromEnableFlags([]),
   );
   return parser.parseDirectives(token);
@@ -121,7 +120,6 @@ CompilationUnit parseFull(Source source) {
   var parser = Parser(
     source,
     AnalysisErrorListener.NULL_LISTENER,
-    languageVersion: null,
     featureSet: FeatureSet.fromEnableFlags([]),
   );
   return parser.parseCompilationUnit(token);

pkg/front_end/test/scanner_fasta_test.dart

@@ -755,10 +755,10 @@ class ScannerTest_Fasta_Direct_UTF8 extends ScannerTest_Fasta_Direct {
 /// Scanner tests that exercise the Fasta scanner directly.
 @reflectiveTest
 class ScannerTest_Fasta_Direct extends ScannerTest_Fasta_Base {
-  LanguageVersionToken languageVersion;
+  fasta.LanguageVersionToken languageVersion;
 
   void languageVersionChanged(
-      Scanner scanner, LanguageVersionToken languageVersion) {
+      Scanner scanner, fasta.LanguageVersionToken languageVersion) {
     this.languageVersion = languageVersion;
   }
 
@@ -972,11 +972,11 @@ main() {}
     token = token.precedingComments;
     while (token != null) {
       if (index == versionIndex) {
-        if (token is! LanguageVersionToken) {
+        if (token is! fasta.LanguageVersionToken) {
           fail('Expected version comment at index $index');
         }
       } else {
-        if (token is LanguageVersionToken) {
+        if (token is fasta.LanguageVersionToken) {
           fail('Did not expect version comment at index $index');
         }
       }

pkg/front_end/tool/fasta_perf.dart

@@ -218,7 +218,7 @@ parseFull(Uri uri, List<int> source) {
 // bodies. So this listener is not feature complete.
 class _PartialAstBuilder extends AstBuilder {
   _PartialAstBuilder(Uri uri)
-      : super(null, null, true, null, FeatureSet.fromEnableFlags([]), uri);
+      : super(null, null, true, FeatureSet.fromEnableFlags([]), uri);
 }
 
 // Invoke the fasta kernel generator for the program starting in [entryUri]

pkg/front_end/tool/perf.dart

@@ -103,7 +103,6 @@ CompilationUnit parseDirectives(Source source) {
   var parser = new Parser(
     source,
     AnalysisErrorListener.NULL_LISTENER,
-    languageVersion: null,
     featureSet: FeatureSet.fromEnableFlags([]),
   );
   return parser.parseDirectives(token);
@@ -128,7 +127,6 @@ CompilationUnit parseFull(Source source) {
   var parser = new Parser(
     source,
     AnalysisErrorListener.NULL_LISTENER,
-    languageVersion: null,
     featureSet: FeatureSet.fromEnableFlags([]),
   );
   var unit = parser.parseCompilationUnit(token);

pkg/nnbd_migration/lib/src/fix_builder.dart

@@ -3,7 +3,6 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:_fe_analyzer_shared/src/flow_analysis/flow_analysis.dart';
-import 'package:_fe_analyzer_shared/src/scanner/token_impl.dart';
 import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';