pkg/_fe_analyzer_shared/lib/src/parser/parser_impl.dart

// Copyright (c) 2012, 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 _fe_analyzer_shared.parser.parser;

import 'package:_fe_analyzer_shared/src/parser/type_info_impl.dart';

import '../messages/codes.dart' as codes;

import '../scanner/scanner.dart' show ErrorToken, Token;

import '../scanner/token.dart'
    show
        ASSIGNMENT_PRECEDENCE,
        BeginToken,
        CASCADE_PRECEDENCE,
        EQUALITY_PRECEDENCE,
        Keyword,
        POSTFIX_PRECEDENCE,
        RELATIONAL_PRECEDENCE,
        SELECTOR_PRECEDENCE,
        StringToken,
        SyntheticBeginToken,
        SyntheticKeywordToken,
        SyntheticStringToken,
        SyntheticToken,
        TokenType;

import '../scanner/token_constants.dart'
    show
        BANG_EQ_EQ_TOKEN,
        COMMA_TOKEN,
        DOUBLE_TOKEN,
        EOF_TOKEN,
        EQ_EQ_EQ_TOKEN,
        EQ_TOKEN,
        FUNCTION_TOKEN,
        HASH_TOKEN,
        HEXADECIMAL_TOKEN,
        IDENTIFIER_TOKEN,
        INT_TOKEN,
        KEYWORD_TOKEN,
        LT_TOKEN,
        OPEN_CURLY_BRACKET_TOKEN,
        OPEN_PAREN_TOKEN,
        OPEN_SQUARE_BRACKET_TOKEN,
        SEMICOLON_TOKEN,
        STRING_INTERPOLATION_IDENTIFIER_TOKEN,
        STRING_INTERPOLATION_TOKEN,
        STRING_TOKEN;

import 'assert.dart' show Assert;

import 'async_modifier.dart' show AsyncModifier;

import 'block_kind.dart';

import 'declaration_kind.dart' show DeclarationKind;

import 'directive_context.dart';

import 'formal_parameter_kind.dart'
    show
        FormalParameterKind,
        isMandatoryFormalParameterKind,
        isOptionalPositionalFormalParameterKind;

import 'forwarding_listener.dart' show ForwardingListener, NullListener;

import 'identifier_context.dart'
    show IdentifierContext, looksLikeExpressionStart;

import 'listener.dart' show Listener;

import 'literal_entry_info.dart'
    show
        LiteralEntryInfo,
        computeLiteralEntry,
        looksLikeLiteralEntry,
        simpleEntry;

import 'loop_state.dart' show LoopState;

import 'member_kind.dart' show MemberKind;

import 'modifier_context.dart' show ModifierRecoveryContext, isModifier;

import 'recovery_listeners.dart'
    show
        ClassHeaderRecoveryListener,
        ImportRecoveryListener,
        MixinHeaderRecoveryListener;

import 'token_stream_rewriter.dart'
    show
        TokenStreamRewriter,
        TokenStreamRewriterImpl,
        UndoableTokenStreamRewriter;

import 'type_info.dart'
    show
        TypeInfo,
        TypeParamOrArgInfo,
        computeMethodTypeArguments,
        computeType,
        computeTypeParamOrArg,
        isValidTypeReference,
        noType,
        noTypeParamOrArg;

import 'util.dart'
    show
        findNonZeroLengthToken,
        findPreviousNonZeroLengthToken,
        isLetter,
        isLetterOrDigit,
        isOneOf,
        isOneOfOrEof,
        isWhitespace,
        optional;

/// An event generating parser of Dart programs. This parser expects all tokens
/// in a linked list (aka a token stream).
///
/// The class [Scanner] is used to generate a token stream. See the file
/// [scanner.dart](../scanner.dart).
///
/// Subclasses of the class [Listener] are used to listen to events.
///
/// Most methods of this class belong in one of four major categories: parse
/// methods, peek methods, ensure methods, and skip methods.
///
/// Parse methods all have the prefix `parse`, generate events
/// (by calling methods on [listener]), and return the next token to parse.
/// Some exceptions to this last point are methods such as [parseFunctionBody]
/// and [parseClassOrMixinOrExtensionBody] which return the last token parsed
/// rather than the next token to be parsed.
/// Parse methods are generally named `parseGrammarProductionSuffix`.
/// The suffix can be one of `opt`, or `star`.
/// `opt` means zero or one matches, `star` means zero or more matches.
/// For example, [parseMetadataStar] corresponds to this grammar snippet:
/// `metadata*`, and [parseArgumentsOpt] corresponds to: `arguments?`.
///
/// Peek methods all have the prefix `peek`, do not generate events
/// (except for errors) and may return null.
///
/// Ensure methods all have the prefix `ensure` and may generate events.
/// They return the current token, or insert and return a synthetic token
/// if the current token does not match. For example,
/// [ensureSemicolon] returns the current token if the current token is a
/// semicolon, otherwise inserts a synthetic semicolon in the token stream
/// before the current token and then returns that new synthetic token.
///
/// Skip methods are like parse methods, but all have the prefix `skip`
/// and skip over some parts of the file being parsed.
/// Typically, skip methods generate an event for the structure being skipped,
/// but not for its substructures.
///
/// ## Current Token
///
/// The current token is always to be found in a formal parameter named
/// `token`. This parameter should be the first as this increases the chance
/// that a compiler will place it in a register.
///
/// ## Implementation Notes
///
/// The parser assumes that keywords, built-in identifiers, and other special
/// words (pseudo-keywords) are all canonicalized. To extend the parser to
/// recognize a new identifier, one should modify
/// [keyword.dart](../scanner/keyword.dart) and ensure the identifier is added
/// to the keyword table.
///
/// As a consequence of this, one should not use `==` to compare strings in the
/// parser. One should favor the methods [optional] and [expect] to recognize
/// keywords or identifiers. In some cases, it's possible to compare a token's
/// `stringValue` using [identical], but normally [optional] will suffice.
///
/// Historically, we over-used identical, and when identical is used on objects
/// other than strings, it can often be replaced by `==`.
///
/// ## Flexibility, Extensibility, and Specification
///
/// The parser is designed to be flexible and extensible. Its methods are
/// designed to be overridden in subclasses, so it can be extended to handle
/// unspecified language extension or experiments while everything in this file
/// attempts to follow the specification (unless when it interferes with error
/// recovery).
///
/// We achieve flexibility, extensible, and specification compliance by
/// following a few rules-of-thumb:
///
/// 1. All methods in the parser should be public.
///
/// 2. The methods follow the specified grammar, and do not implement custom
/// extensions, for example, `native`.
///
/// 3. The parser doesn't rewrite the token stream (when dealing with `>>`).
///
/// ### Implementing Extensions
///
/// For various reasons, some Dart language implementations have used
/// custom/unspecified extensions to the Dart grammar. Examples of this
/// includes diet parsing, patch files, `native` keyword, and generic
/// comments. This class isn't supposed to implement any of these
/// features. Instead it provides hooks for those extensions to be implemented
/// in subclasses or listeners. Let's examine how diet parsing and `native`
/// keyword is currently supported by Fasta.
///
/// #### Legacy Implementation of `native` Keyword
///
/// TODO(ahe,danrubel): Remove this section.
///
/// Both dart2js and the Dart VM have used the `native` keyword to mark methods
/// that couldn't be implemented in the Dart language and needed to be
/// implemented in JavaScript or C++, respectively. An example of the syntax
/// extension used by the Dart VM is:
///
///     nativeFunction() native "NativeFunction";
///
/// When attempting to parse this function, the parser eventually calls
/// [parseFunctionBody]. This method will report an unrecoverable error to the
/// listener with the code [fasta.messageExpectedFunctionBody]. The listener can
/// then look at the error code and the token and use the methods in
/// [native_support.dart](native_support.dart) to parse the native syntax.
///
/// #### Implementation of Diet Parsing
///
/// We call it _diet_ _parsing_ when the parser skips parts of a file. Both
/// dart2js and the Dart VM have been relying on this from early on as it allows
/// them to more quickly compile small programs that use small parts of big
/// libraries. It's also become an integrated part of how Fasta builds up
/// outlines before starting to parse method bodies.
///
/// When looking through this parser, you'll find a number of unused methods
/// starting with `skip`. These methods are only used by subclasses, such as
/// [ClassMemberParser](class_member_parser.dart) and
/// [TopLevelParser](top_level_parser.dart). These methods violate the
/// principle above about following the specified grammar, and originally lived
/// in subclasses. However, we realized that these methods were so widely used
/// and hard to maintain in subclasses, that it made sense to move them here.
///
/// ### Specification and Error Recovery
///
/// To improve error recovery, the parser will inform the listener of
/// recoverable errors and continue to parse.  An example of a recoverable
/// error is:
///
///     Error: Asynchronous for-loop can only be used in 'async' or 'async*'...
///     main() { await for (var x in []) {} }
///              ^^^^^
///
/// ### Legacy Error Recovery
///
/// What's described below will be phased out in preference of the parser
/// reporting and recovering from syntax errors. The motivation for this is
/// that we have multiple listeners that use the parser, and this will ensure
/// consistency.
///
/// For unrecoverable errors, the parser will ask the listener for help to
/// recover from the error. We haven't made much progress on these kinds of
/// errors, so in most cases, the parser aborts by skipping to the end of file.
///
/// Historically, this parser has been rather lax in what it allows, and
/// deferred the enforcement of some syntactical rules to subsequent phases. It
/// doesn't matter how we got there, only that we've identified that it's
/// easier if the parser reports as many errors it can, but informs the
/// listener if the error is recoverable or not.
class Parser {
  Listener listener;

  Uri? get uri => listener.uri;

  bool mayParseFunctionExpressions = true;

  /// Represents parser state: what asynchronous syntax is allowed in the
  /// function being currently parsed. In rare situations, this can be set by
  /// external clients, for example, to parse an expression outside a function.
  AsyncModifier asyncState = AsyncModifier.Sync;

  // TODO(danrubel): The [loopState] and associated functionality in the
  // [Parser] duplicates work that the resolver needs to do when resolving
  // break/continue targets. Long term, this state and functionality will be
  // removed from the [Parser] class and the resolver will be responsible
  // for generating all break/continue error messages.

  /// Represents parser state: whether parsing outside a loop,
  /// inside a loop, or inside a switch. This is used to determine whether
  /// break and continue statements are allowed.
  LoopState loopState = LoopState.OutsideLoop;

  /// A rewriter for inserting synthetic tokens.
  /// Access using [rewriter] for lazy initialization.
  TokenStreamRewriter? cachedRewriter;

  TokenStreamRewriter get rewriter {
    return cachedRewriter ??= new TokenStreamRewriterImpl();
  }

  Parser(this.listener)
      : assert(listener != null); // ignore:unnecessary_null_comparison

  bool get inGenerator {
    return asyncState == AsyncModifier.AsyncStar ||
        asyncState == AsyncModifier.SyncStar;
  }

  bool get inAsync {
    return asyncState == AsyncModifier.Async ||
        asyncState == AsyncModifier.AsyncStar;
  }

  bool get inPlainSync => asyncState == AsyncModifier.Sync;

  bool get isBreakAllowed => loopState != LoopState.OutsideLoop;

  bool get isContinueAllowed => loopState == LoopState.InsideLoop;

  bool get isContinueWithLabelAllowed => loopState != LoopState.OutsideLoop;

  /// Parse a compilation unit.
  ///
  /// This method is only invoked from outside the parser. As a result, this
  /// method takes the next token to be consumed rather than the last consumed
  /// token and returns the token after the last consumed token rather than the
  /// last consumed token.
  ///
  /// ```
  /// libraryDefinition:
  ///   scriptTag?
  ///   libraryName?
  ///   importOrExport*
  ///   partDirective*
  ///   topLevelDefinition*
  /// ;
  ///
  /// partDeclaration:
  ///   partHeader topLevelDefinition*
  /// ;
  /// ```
  Token parseUnit(Token token) {
    // Skip over error tokens and report them at the end
    // so that the parser has the chance to adjust the error location.
    Token errorToken = token;
    token = skipErrorTokens(errorToken);

    listener.beginCompilationUnit(token);
    int count = 0;
    DirectiveContext directiveState = new DirectiveContext();
    token = syntheticPreviousToken(token);
    if (identical(token.next!.type, TokenType.SCRIPT_TAG)) {
      directiveState.checkScriptTag(this, token.next!);
      token = parseScript(token);
    }
    while (!token.next!.isEof) {
      final Token start = token.next!;
      token = parseTopLevelDeclarationImpl(token, directiveState);
      listener.endTopLevelDeclaration(token.next!);
      count++;
      if (start == token.next!) {
        // Recovery:
        // If progress has not been made reaching the end of the token stream,
        // then report an error and skip the current token.
        token = token.next!;
        listener.beginMetadataStar(token);
        listener.endMetadataStar(/* count = */ 0);
        reportRecoverableErrorWithToken(
            token, codes.templateExpectedDeclaration);
        listener.handleInvalidTopLevelDeclaration(token);
        listener.endTopLevelDeclaration(token.next!);
        count++;
      }
    }
    token = token.next!;
    reportAllErrorTokens(errorToken);
    listener.endCompilationUnit(count, token);
    // Clear fields that could lead to memory leak.
    cachedRewriter = null;
    return token;
  }

  /// This method exists for analyzer compatibility only
  /// and will be removed once analyzer/fasta integration is complete.
  ///
  /// Similar to [parseUnit], this method parses a compilation unit,
  /// but stops when it reaches the first declaration or EOF.
  ///
  /// This method is only invoked from outside the parser. As a result, this
  /// method takes the next token to be consumed rather than the last consumed
  /// token and returns the token after the last consumed token rather than the
  /// last consumed token.
  Token parseDirectives(Token token) {
    listener.beginCompilationUnit(token);
    int count = 0;
    DirectiveContext directiveState = new DirectiveContext();
    token = syntheticPreviousToken(token);
    while (!token.next!.isEof) {
      final Token start = token.next!;
      final String? nextValue = start.next!.stringValue;

      // If a built-in keyword is being used as function name, then stop.
      if (identical(nextValue, '.') ||
          identical(nextValue, '<') ||
          identical(nextValue, '(')) {
        break;
      }

      if (identical(token.next!.type, TokenType.SCRIPT_TAG)) {
        directiveState.checkScriptTag(this, token.next!);
        token = parseScript(token);
      } else {
        token = parseMetadataStar(token);
        Token keyword = token.next!;
        final String? value = keyword.stringValue;
        if (identical(value, 'import')) {
          directiveState.checkImport(this, keyword);
          token = parseImport(keyword);
        } else if (identical(value, 'export')) {
          directiveState.checkExport(this, keyword);
          token = parseExport(keyword);
        } else if (identical(value, 'library')) {
          directiveState.checkLibrary(this, keyword);
          token = parseLibraryName(keyword);
        } else if (identical(value, 'part')) {
          token = parsePartOrPartOf(keyword, directiveState);
        } else if (identical(value, ';')) {
          token = start;
          listener.handleDirectivesOnly();
        } else {
          listener.handleDirectivesOnly();
          break;
        }
      }
      listener.endTopLevelDeclaration(token.next!);
    }
    token = token.next!;
    listener.endCompilationUnit(count, token);
    // Clear fields that could lead to memory leak.
    cachedRewriter = null;
    return token;
  }

  /// Parse a top-level declaration.
  ///
  /// This method is only invoked from outside the parser. As a result, this
  /// method takes the next token to be consumed rather than the last consumed
  /// token and returns the token after the last consumed token rather than the
  /// last consumed token.
  Token parseTopLevelDeclaration(Token token) {
    token = parseTopLevelDeclarationImpl(
            syntheticPreviousToken(token), /* directiveState = */ null)
        .next!;
    listener.endTopLevelDeclaration(token);
    return token;
  }

  /// ```
  /// topLevelDefinition:
  ///   classDefinition |
  ///   enumType |
  ///   typeAlias |
  ///   'external'? functionSignature ';' |
  ///   'external'? getterSignature ';' |
  ///   'external''? setterSignature ';' |
  ///   functionSignature functionBody |
  ///   returnType? 'get' identifier functionBody |
  ///   returnType? 'set' identifier formalParameterList functionBody |
  ///   ('final' | 'const') type? staticFinalDeclarationList ';' |
  ///   variableDeclaration ';'
  /// ;
  /// ```
  Token parseTopLevelDeclarationImpl(
      Token token, DirectiveContext? directiveState) {
    token = parseMetadataStar(token);
    Token next = token.next!;
    if (next.isTopLevelKeyword) {
      return parseTopLevelKeywordDeclaration(token, next, directiveState);
    }
    Token start = token;
    // Skip modifiers to find a top level keyword or identifier
    if (next.isModifier) {
      if (optional('var', next) ||
          optional('late', next) ||
          ((optional('const', next) || optional('final', next)) &&
              // Ignore `const class` and `final class` so that it is reported
              // below as an invalid modifier on a class.
              !optional('class', next.next!))) {
        directiveState?.checkDeclaration();
        return parseTopLevelMemberImpl(token);
      }
      while (token.next!.isModifier) {
        token = token.next!;
      }
    }
    next = token.next!;
    if (next.isTopLevelKeyword) {
      return parseTopLevelKeywordDeclaration(start, next, directiveState);
    } else if (next.isKeywordOrIdentifier) {
      // TODO(danrubel): improve parseTopLevelMember
      // so that we don't parse modifiers twice.
      directiveState?.checkDeclaration();
      return parseTopLevelMemberImpl(start);
    } else if (start.next != next) {
      directiveState?.checkDeclaration();
      // Handle the edge case where a modifier is being used as an identifier
      return parseTopLevelMemberImpl(start);
    }
    // Recovery
    if (next.isOperator && optional('(', next.next!)) {
      // This appears to be a top level operator declaration, which is invalid.
      reportRecoverableError(next, codes.messageTopLevelOperator);
      // Insert a synthetic identifier
      // and continue parsing as a top level function.
      rewriter.insertSyntheticIdentifier(
          next, '#synthetic_function_${next.charOffset}');
      return parseTopLevelMemberImpl(next);
    }
    // Ignore any preceding modifiers and just report the unexpected token
    listener.beginTopLevelMember(next);
    return parseInvalidTopLevelDeclaration(token);
  }

  /// Parse the modifiers before the `class` keyword.
  /// Return the first `abstract` modifier or `null` if not found.
  Token? parseClassDeclarationModifiers(Token start, Token keyword) {
    Token modifier = start.next!;
    while (modifier != keyword) {
      if (optional('abstract', modifier)) {
        parseTopLevelKeywordModifiers(modifier, keyword);
        return modifier;
      } else {
        // Recovery
        reportTopLevelModifierError(modifier, keyword);
      }
      modifier = modifier.next!;
    }
    return null;
  }

  /// Report errors on any modifiers before the specified keyword.
  void parseTopLevelKeywordModifiers(Token start, Token keyword) {
    Token modifier = start.next!;
    while (modifier != keyword) {
      // Recovery
      reportTopLevelModifierError(modifier, keyword);
      modifier = modifier.next!;
    }
  }

  // Report an error for the given modifier preceding a top level keyword
  // such as `import` or `class`.
  void reportTopLevelModifierError(Token modifier, Token afterModifiers) {
    if (optional('const', modifier) && optional('class', afterModifiers)) {
      reportRecoverableError(modifier, codes.messageConstClass);
    } else if (optional('external', modifier)) {
      if (optional('class', afterModifiers)) {
        reportRecoverableError(modifier, codes.messageExternalClass);
      } else if (optional('enum', afterModifiers)) {
        reportRecoverableError(modifier, codes.messageExternalEnum);
      } else if (optional('typedef', afterModifiers)) {
        reportRecoverableError(modifier, codes.messageExternalTypedef);
      } else {
        reportRecoverableErrorWithToken(
            modifier, codes.templateExtraneousModifier);
      }
    } else {
      reportRecoverableErrorWithToken(
          modifier, codes.templateExtraneousModifier);
    }
  }

  /// Parse any top-level declaration that begins with a keyword.
  /// [start] is the token before any modifiers preceding [keyword].
  Token parseTopLevelKeywordDeclaration(
      Token start, Token keyword, DirectiveContext? directiveState) {
    assert(keyword.isTopLevelKeyword);
    final String? value = keyword.stringValue;
    if (identical(value, 'class')) {
      directiveState?.checkDeclaration();
      Token? abstractToken = parseClassDeclarationModifiers(start, keyword);
      return parseClassOrNamedMixinApplication(abstractToken, keyword);
    } else if (identical(value, 'enum')) {
      directiveState?.checkDeclaration();
      parseTopLevelKeywordModifiers(start, keyword);
      return parseEnum(keyword);
    } else {
      // The remaining top level keywords are built-in keywords
      // and can be used in a top level declaration
      // as an identifier such as "abstract<T>() => 0;"
      // or as a prefix such as "abstract.A b() => 0;".
      String? nextValue = keyword.next!.stringValue;
      if (identical(nextValue, '(') || identical(nextValue, '.')) {
        directiveState?.checkDeclaration();
        return parseTopLevelMemberImpl(start);
      } else if (identical(nextValue, '<')) {
        if (identical(value, 'extension')) {
          // The name in an extension declaration is optional:
          // `extension<T> on ...`
          Token? endGroup = keyword.next!.endGroup;
          if (endGroup != null && optional('on', endGroup.next!)) {
            directiveState?.checkDeclaration();
            return parseExtension(keyword);
          }
        }
        directiveState?.checkDeclaration();
        return parseTopLevelMemberImpl(start);
      } else {
        parseTopLevelKeywordModifiers(start, keyword);
        if (identical(value, 'import')) {
          directiveState?.checkImport(this, keyword);
          return parseImport(keyword);
        } else if (identical(value, 'export')) {
          directiveState?.checkExport(this, keyword);
          return parseExport(keyword);
        } else if (identical(value, 'typedef')) {
          directiveState?.checkDeclaration();
          return parseTypedef(keyword);
        } else if (identical(value, 'mixin')) {
          directiveState?.checkDeclaration();
          return parseMixin(keyword);
        } else if (identical(value, 'extension')) {
          directiveState?.checkDeclaration();
          return parseExtension(keyword);
        } else if (identical(value, 'part')) {
          return parsePartOrPartOf(keyword, directiveState);
        } else if (identical(value, 'library')) {
          directiveState?.checkLibrary(this, keyword);
          return parseLibraryName(keyword);
        }
      }
    }

    throw "Internal error: Unhandled top level keyword '$value'.";
  }

  /// ```
  /// libraryDirective:
  ///   'library' qualified ';'
  /// ;
  /// ```
  Token parseLibraryName(Token libraryKeyword) {
    assert(optional('library', libraryKeyword));
    listener.beginUncategorizedTopLevelDeclaration(libraryKeyword);
    listener.beginLibraryName(libraryKeyword);
    Token token = parseQualified(libraryKeyword, IdentifierContext.libraryName,
        IdentifierContext.libraryNameContinuation);
    token = ensureSemicolon(token);
    listener.endLibraryName(libraryKeyword, token);
    return token;
  }

  /// ```
  /// importPrefix:
  ///   'deferred'? 'as' identifier
  /// ;
  /// ```
  Token parseImportPrefixOpt(Token token) {
    Token next = token.next!;
    if (optional('deferred', next) && optional('as', next.next!)) {
      Token deferredToken = next;
      Token asKeyword = next.next!;
      token = ensureIdentifier(
          asKeyword, IdentifierContext.importPrefixDeclaration);
      listener.handleImportPrefix(deferredToken, asKeyword);
    } else if (optional('as', next)) {
      Token asKeyword = next;
      token = ensureIdentifier(next, IdentifierContext.importPrefixDeclaration);
      listener.handleImportPrefix(/* deferredKeyword = */ null, asKeyword);
    } else {
      listener.handleImportPrefix(
          /* deferredKeyword = */ null,
          /* asKeyword = */ null);
    }
    return token;
  }

  /// ```
  /// importDirective:
  ///   'import' uri ('if' '(' test ')' uri)* importPrefix? combinator* ';'
  /// ;
  /// ```
  Token parseImport(Token importKeyword) {
    assert(optional('import', importKeyword));
    listener.beginUncategorizedTopLevelDeclaration(importKeyword);
    listener.beginImport(importKeyword);
    Token token = ensureLiteralString(importKeyword);
    Token uri = token;
    token = parseConditionalUriStar(token);
    token = parseImportPrefixOpt(token);
    token = parseCombinatorStar(token).next!;
    if (optional(';', token)) {
      listener.endImport(importKeyword, token);
      return token;
    } else {
      // Recovery
      listener.endImport(importKeyword, /* semicolon = */ null);
      return parseImportRecovery(uri);
    }
  }

  /// Recover given out-of-order clauses in an import directive where [token] is
  /// the import keyword.
  Token parseImportRecovery(Token token) {
    final Listener primaryListener = listener;
    final ImportRecoveryListener recoveryListener =
        new ImportRecoveryListener();

    // Reparse to determine which clauses have already been parsed
    // but intercept the events so they are not sent to the primary listener
    listener = recoveryListener;
    token = parseConditionalUriStar(token);
    token = parseImportPrefixOpt(token);
    token = parseCombinatorStar(token);

    Token? firstDeferredKeyword = recoveryListener.deferredKeyword;
    bool hasPrefix = recoveryListener.asKeyword != null;
    bool hasCombinator = recoveryListener.hasCombinator;

    // Update the recovery listener to forward subsequent events
    // to the primary listener
    recoveryListener.listener = primaryListener;

    // Parse additional out-of-order clauses.
    Token? semicolon;
    do {
      Token start = token.next!;

      // Check for extraneous token in the middle of an import statement.
      token = skipUnexpectedTokenOpt(
          token, const <String>['if', 'deferred', 'as', 'hide', 'show', ';']);

      // During recovery, clauses are parsed in the same order
      // and generate the same events as in the parseImport method above.
      recoveryListener.clear();
      token = parseConditionalUriStar(token);
      if (recoveryListener.ifKeyword != null) {
        if (firstDeferredKeyword != null) {
          // TODO(danrubel): report error indicating conditional should
          // be moved before deferred keyword
        } else if (hasPrefix) {
          // TODO(danrubel): report error indicating conditional should
          // be moved before prefix clause
        } else if (hasCombinator) {
          // TODO(danrubel): report error indicating conditional should
          // be moved before combinators
        }
      }

      if (optional('deferred', token.next!) &&
          !optional('as', token.next!.next!)) {
        listener.handleImportPrefix(token.next!, /* asKeyword = */ null);
        token = token.next!;
      } else {
        token = parseImportPrefixOpt(token);
      }
      if (recoveryListener.deferredKeyword != null) {
        if (firstDeferredKeyword != null) {
          reportRecoverableError(recoveryListener.deferredKeyword!,
              codes.messageDuplicateDeferred);
        } else {
          if (hasPrefix) {
            reportRecoverableError(recoveryListener.deferredKeyword!,
                codes.messageDeferredAfterPrefix);
          }
          firstDeferredKeyword = recoveryListener.deferredKeyword;
        }
      }
      if (recoveryListener.asKeyword != null) {
        if (hasPrefix) {
          reportRecoverableError(
              recoveryListener.asKeyword!, codes.messageDuplicatePrefix);
        } else {
          if (hasCombinator) {
            reportRecoverableError(recoveryListener.asKeyword!,
                codes.messagePrefixAfterCombinator);
          }
          hasPrefix = true;
        }
      }

      token = parseCombinatorStar(token);
      hasCombinator = hasCombinator || recoveryListener.hasCombinator;

      if (optional(';', token.next!)) {
        semicolon = token.next!;
      } else if (identical(start, token.next!)) {
        // If no forward progress was made, insert ';' so that we exit loop.
        semicolon = ensureSemicolon(token);
      }
      listener.handleRecoverImport(semicolon);
    } while (semicolon == null);

    if (firstDeferredKeyword != null && !hasPrefix) {
      reportRecoverableError(
          firstDeferredKeyword, codes.messageMissingPrefixInDeferredImport);
    }

    return semicolon;
  }

  /// ```
  /// conditionalUris:
  ///   conditionalUri*
  /// ;
  /// ```
  Token parseConditionalUriStar(Token token) {
    listener.beginConditionalUris(token.next!);
    int count = 0;
    while (optional('if', token.next!)) {
      count++;
      token = parseConditionalUri(token);
    }
    listener.endConditionalUris(count);
    return token;
  }

  /// ```
  /// conditionalUri:
  ///   'if' '(' dottedName ('==' literalString)? ')' uri
  /// ;
  /// ```
  Token parseConditionalUri(Token token) {
    Token ifKeyword = token = token.next!;
    assert(optional('if', token));
    listener.beginConditionalUri(token);
    Token leftParen = token.next!;
    if (!optional('(', leftParen)) {
      reportRecoverableError(
          leftParen, codes.templateExpectedButGot.withArguments('('));
      leftParen = rewriter.insertParens(token, /* includeIdentifier = */ true);
    }
    token = parseDottedName(leftParen);
    Token next = token.next!;
    Token? equalitySign;
    if (optional('==', next)) {
      equalitySign = next;
      token = ensureLiteralString(next);
      next = token.next!;
    }
    if (next != leftParen.endGroup) {
      Token endGroup = leftParen.endGroup!;
      if (endGroup.isSynthetic) {
        // The scanner did not place the synthetic ')' correctly, so move it.
        next = rewriter.moveSynthetic(token, endGroup);
      } else {
        reportRecoverableErrorWithToken(next, codes.templateUnexpectedToken);
        next = endGroup;
      }
    }
    token = next;
    assert(optional(')', token));

    token = ensureLiteralString(token);
    listener.endConditionalUri(ifKeyword, leftParen, equalitySign);
    return token;
  }

  /// ```
  /// dottedName:
  ///   identifier ('.' identifier)*
  /// ;
  /// ```
  Token parseDottedName(Token token) {
    token = ensureIdentifier(token, IdentifierContext.dottedName);
    Token firstIdentifier = token;
    int count = 1;
    while (optional('.', token.next!)) {
      token = ensureIdentifier(
          token.next!, IdentifierContext.dottedNameContinuation);
      count++;
    }
    listener.handleDottedName(count, firstIdentifier);
    return token;
  }

  /// ```
  /// exportDirective:
  ///   'export' uri conditional-uris* combinator* ';'
  /// ;
  /// ```
  Token parseExport(Token exportKeyword) {
    assert(optional('export', exportKeyword));
    listener.beginUncategorizedTopLevelDeclaration(exportKeyword);
    listener.beginExport(exportKeyword);
    Token token = ensureLiteralString(exportKeyword);
    token = parseConditionalUriStar(token);
    token = parseCombinatorStar(token);
    token = ensureSemicolon(token);
    listener.endExport(exportKeyword, token);
    return token;
  }

  /// ```
  /// combinators:
  ///   (hideCombinator | showCombinator)*
  /// ;
  /// ```
  Token parseCombinatorStar(Token token) {
    Token next = token.next!;
    listener.beginCombinators(next);
    int count = 0;
    while (true) {
      String? value = next.stringValue;
      if (identical('hide', value)) {
        token = parseHide(token);
      } else if (identical('show', value)) {
        token = parseShow(token);
      } else {
        listener.endCombinators(count);
        break;
      }
      next = token.next!;
      count++;
    }
    return token;
  }

  /// ```
  /// hideCombinator:
  ///   'hide' identifierList
  /// ;
  /// ```
  Token parseHide(Token token) {
    Token hideKeyword = token.next!;
    assert(optional('hide', hideKeyword));
    listener.beginHide(hideKeyword);
    token = parseIdentifierList(hideKeyword);
    listener.endHide(hideKeyword);
    return token;
  }

  /// ```
  /// showCombinator:
  ///   'show' identifierList
  /// ;
  /// ```
  Token parseShow(Token token) {
    Token showKeyword = token.next!;
    assert(optional('show', showKeyword));
    listener.beginShow(showKeyword);
    token = parseIdentifierList(showKeyword);
    listener.endShow(showKeyword);
    return token;
  }

  /// ```
  /// identifierList:
  ///   identifier (',' identifier)*
  /// ;
  /// ```
  Token parseIdentifierList(Token token) {
    token = ensureIdentifier(token, IdentifierContext.combinator);
    int count = 1;
    while (optional(',', token.next!)) {
      token = ensureIdentifier(token.next!, IdentifierContext.combinator);
      count++;
    }
    listener.handleIdentifierList(count);
    return token;
  }

  /// ```
  /// typeList:
  ///   type (',' type)*
  /// ;
  /// ```
  Token parseTypeList(Token token) {
    listener.beginTypeList(token.next!);
    token =
        computeType(token, /* required = */ true).ensureTypeOrVoid(token, this);
    int count = 1;
    while (optional(',', token.next!)) {
      token = computeType(token.next!, /* required = */ true)
          .ensureTypeOrVoid(token.next!, this);
      count++;
    }
    listener.endTypeList(count);
    return token;
  }

  Token parsePartOrPartOf(Token partKeyword, DirectiveContext? directiveState) {
    assert(optional('part', partKeyword));
    listener.beginUncategorizedTopLevelDeclaration(partKeyword);
    if (optional('of', partKeyword.next!)) {
      directiveState?.checkPartOf(this, partKeyword);
      return parsePartOf(partKeyword);
    } else {
      directiveState?.checkPart(this, partKeyword);
      return parsePart(partKeyword);
    }
  }

  /// ```
  /// partDirective:
  ///   'part' uri ';'
  /// ;
  /// ```
  Token parsePart(Token partKeyword) {
    assert(optional('part', partKeyword));
    listener.beginPart(partKeyword);
    Token token = ensureLiteralString(partKeyword);
    token = ensureSemicolon(token);
    listener.endPart(partKeyword, token);
    return token;
  }

  /// ```
  /// partOfDirective:
  ///   'part' 'of' (qualified | uri) ';'
  /// ;
  /// ```
  Token parsePartOf(Token partKeyword) {
    Token ofKeyword = partKeyword.next!;
    assert(optional('part', partKeyword));
    assert(optional('of', ofKeyword));
    listener.beginPartOf(partKeyword);
    bool hasName = ofKeyword.next!.isIdentifier;
    Token token;
    if (hasName) {
      token = parseQualified(ofKeyword, IdentifierContext.partName,
          IdentifierContext.partNameContinuation);
    } else {
      token = ensureLiteralString(ofKeyword);
    }
    token = ensureSemicolon(token);
    listener.endPartOf(partKeyword, ofKeyword, token, hasName);
    return token;
  }

  /// ```
  /// metadata:
  ///   annotation*
  /// ;
  /// ```
  Token parseMetadataStar(Token token) {
    listener.beginMetadataStar(token.next!);
    int count = 0;
    while (optional('@', token.next!)) {
      token = parseMetadata(token);
      count++;
    }
    listener.endMetadataStar(count);
    return token;
  }

  /// ```
  /// annotation:
  ///   '@' qualified ('.' identifier)? arguments?
  /// ;
  /// ```
  Token parseMetadata(Token token) {
    Token atToken = token.next!;
    assert(optional('@', atToken));
    listener.beginMetadata(atToken);
    token = ensureIdentifier(atToken, IdentifierContext.metadataReference);
    token =
        parseQualifiedRestOpt(token, IdentifierContext.metadataContinuation);
    bool hasTypeArguments = optional("<", token.next!);
    token = computeTypeParamOrArg(token).parseArguments(token, this);
    Token? period = null;
    if (optional('.', token.next!)) {
      period = token.next!;
      token = ensureIdentifier(
          period, IdentifierContext.metadataContinuationAfterTypeArguments);
    }
    if (hasTypeArguments && !optional("(", token.next!)) {
      reportRecoverableError(
          token, codes.messageMetadataTypeArgumentsUninstantiated);
    }
    token = parseArgumentsOpt(token);
    listener.endMetadata(atToken, period, token.next!);
    return token;
  }

  /// ```
  /// scriptTag:
  ///   '#!' (˜NEWLINE)* NEWLINE
  /// ;
  /// ```
  Token parseScript(Token token) {
    token = token.next!;
    assert(identical(token.type, TokenType.SCRIPT_TAG));
    listener.handleScript(token);
    return token;
  }

  /// ```
  /// typeAlias:
  ///   metadata 'typedef' typeAliasBody |
  ///   metadata 'typedef' identifier typeParameters? '=' functionType ';'
  /// ;
  ///
  /// functionType:
  ///   returnType? 'Function' typeParameters? parameterTypeList
  ///
  /// typeAliasBody:
  ///   functionTypeAlias
  /// ;
  ///
  /// functionTypeAlias:
  ///   functionPrefix typeParameters? formalParameterList ‘;’
  /// ;
  ///
  /// functionPrefix:
  ///   returnType? identifier
  /// ;
  /// ```
  Token parseTypedef(Token typedefKeyword) {
    assert(optional('typedef', typedefKeyword));
    listener.beginUncategorizedTopLevelDeclaration(typedefKeyword);
    listener.beginFunctionTypeAlias(typedefKeyword);
    TypeInfo typeInfo = computeType(typedefKeyword, /* required = */ false);
    Token token = typeInfo.skipType(typedefKeyword);
    Token next = token.next!;
    Token? equals;
    TypeParamOrArgInfo typeParam =
        computeTypeParamOrArg(next, /* inDeclaration = */ true);
    if (typeInfo == noType && optional('=', typeParam.skip(next).next!)) {
      // New style typedef, e.g. typedef foo = void Function();".

      // Parse as recovered here to 'force' using it as an identifier as we've
      // already established that the next token is the equal sign we're looking
      // for.
      token = ensureIdentifierPotentiallyRecovered(token,
          IdentifierContext.typedefDeclaration, /* isRecovered = */ true);

      token = typeParam.parseVariables(token, this);
      next = token.next!;
      // parseVariables rewrites so even though we checked in the if,
      // we might not have an equal here now.
      if (!optional('=', next) && optional('=', next.next!)) {
        // Recovery after recovery: A token was inserted, but we'll skip it now
        // to get more in line with what we thought in the if before.
        next = next.next!;
      }
      if (optional('=', next)) {
        equals = next;
        TypeInfo type = computeType(equals, /* required = */ true);
        if (!type.isFunctionType) {
          // Recovery: In certain cases insert missing 'Function' and missing
          // parens.
          Token skippedType = type.skipType(equals);
          if (optional('(', skippedType.next!) &&
              skippedType.next!.endGroup != null &&
              optional(';', skippedType.next!.endGroup!.next!)) {
            // Turn "<return type>? '(' <whatever> ')';"
            // into "<return type>? Function '(' <whatever> ')';".
            // Assume the type is meant as the return type.
            Token functionToken =
                rewriter.insertSyntheticKeyword(skippedType, Keyword.FUNCTION);
            reportRecoverableError(functionToken,
                codes.templateExpectedButGot.withArguments('Function'));
            type = computeType(equals, /* required = */ true);
          } else if (type is NoType &&
              optional('<', skippedType.next!) &&
              skippedType.next!.endGroup != null) {
            // Recover these two:
            // "<whatever>;" => "Function<whatever>();"
            // "<whatever>(<whatever>);" => "Function<whatever>(<whatever>);"
            Token endGroup = skippedType.next!.endGroup!;
            bool recover = false;
            if (optional(';', endGroup.next!)) {
              // Missing parenthesis. Insert them.
              // Turn "<whatever>;" in to "<whatever>();"
              // Insert missing 'Function' below.
              reportRecoverableError(endGroup,
                  missingParameterMessage(MemberKind.FunctionTypeAlias));
              rewriter.insertParens(endGroup, /*includeIdentifier =*/ false);
              recover = true;
            } else if (optional('(', endGroup.next!) &&
                endGroup.next!.endGroup != null &&
                optional(';', endGroup.next!.endGroup!.next!)) {
              // "<whatever>(<whatever>);". Insert missing 'Function' below.
              recover = true;
            }

            if (recover) {
              // Assume the '<' indicates type arguments to the function.
              // Insert 'Function' before them.
              Token functionToken =
                  rewriter.insertSyntheticKeyword(equals, Keyword.FUNCTION);
              reportRecoverableError(functionToken,
                  codes.templateExpectedButGot.withArguments('Function'));
              type = computeType(equals, /* required = */ true);
            }
          } else {
            // E.g. "typedef j = foo;" -- don't attempt any recovery.
          }
        }
        token = type.ensureTypeOrVoid(equals, this);
      } else {
        // A rewrite caused the = to disappear
        token = parseFormalParametersRequiredOpt(
            next, MemberKind.FunctionTypeAlias);
      }
    } else {
      // Old style typedef, e.g. "typedef void foo();".
      token = typeInfo.parseType(typedefKeyword, this);
      next = token.next!;
      bool isIdentifierRecovered = false;
      if (next.kind != IDENTIFIER_TOKEN &&
          optional('(', typeParam.skip(next).next!)) {
        // Recovery: Not a valid identifier, but is used as such.
        isIdentifierRecovered = true;
      }
      token = ensureIdentifierPotentiallyRecovered(
          token, IdentifierContext.typedefDeclaration, isIdentifierRecovered);
      token = typeParam.parseVariables(token, this);
      token =
          parseFormalParametersRequiredOpt(token, MemberKind.FunctionTypeAlias);
    }
    token = ensureSemicolon(token);
    listener.endFunctionTypeAlias(typedefKeyword, equals, token);
    return token;
  }

  /// Parse a mixin application starting from `with`. Assumes that the first
  /// type has already been parsed.
  Token parseMixinApplicationRest(Token token) {
    Token withKeyword = token.next!;
    if (!optional('with', withKeyword)) {
      // Recovery: Report an error and insert synthetic `with` clause.
      reportRecoverableError(
          withKeyword, codes.templateExpectedButGot.withArguments('with'));
      withKeyword = rewriter.insertSyntheticKeyword(token, Keyword.WITH);
      if (!isValidTypeReference(withKeyword.next!)) {
        rewriter.insertSyntheticIdentifier(withKeyword);
      }
    }
    token = parseTypeList(withKeyword);
    listener.handleNamedMixinApplicationWithClause(withKeyword);
    return token;
  }

  Token parseWithClauseOpt(Token token) {
    // <mixins> ::= with <typeNotVoidList>
    Token withKeyword = token.next!;
    if (optional('with', withKeyword)) {
      token = parseTypeList(withKeyword);
      listener.handleClassWithClause(withKeyword);
    } else {
      listener.handleClassNoWithClause();
    }
    return token;
  }

  /// Parse the formal parameters of a getter (which shouldn't have parameters)
  /// or function or method.
  Token parseGetterOrFormalParameters(
      Token token, Token name, bool isGetter, MemberKind kind) {
    Token next = token.next!;
    if (optional("(", next)) {
      if (isGetter) {
        reportRecoverableError(next, codes.messageGetterWithFormals);
      }
      token = parseFormalParameters(token, kind);
    } else if (isGetter) {
      listener.handleNoFormalParameters(next, kind);
    } else {
      // Recovery
      if (optional('operator', name)) {
        Token next = name.next!;
        if (next.isOperator) {
          name = next;
        } else if (isUnaryMinus(next)) {
          name = next.next!;
        }
      }
      reportRecoverableError(name, missingParameterMessage(kind));
      token = rewriter.insertParens(token, /* includeIdentifier = */ false);
      token = parseFormalParametersRest(token, kind);
    }
    return token;
  }

  Token parseFormalParametersOpt(Token token, MemberKind kind) {
    Token next = token.next!;
    if (optional('(', next)) {
      token = parseFormalParameters(token, kind);
    } else {
      listener.handleNoFormalParameters(next, kind);
    }
    return token;
  }

  Token skipFormalParameters(Token token, MemberKind kind) {
    return skipFormalParametersRest(token.next!, kind);
  }

  Token skipFormalParametersRest(Token token, MemberKind kind) {
    assert(optional('(', token));
    // TODO(ahe): Shouldn't this be `beginFormalParameters`?
    listener.beginOptionalFormalParameters(token);
    Token closeBrace = token.endGroup!;
    assert(optional(')', closeBrace));
    listener.endFormalParameters(/* count = */ 0, token, closeBrace, kind);
    return closeBrace;
  }

  /// Parses the formal parameter list of a function.
  ///
  /// If `kind == MemberKind.GeneralizedFunctionType`, then names may be
  /// omitted (except for named arguments). Otherwise, types may be omitted.
  Token parseFormalParametersRequiredOpt(Token token, MemberKind kind) {
    Token next = token.next!;
    if (!optional('(', next)) {
      reportRecoverableError(next, missingParameterMessage(kind));
      next = rewriter.insertParens(token, /* includeIdentifier = */ false);
    }
    return parseFormalParametersRest(next, kind);
  }

  /// Parses the formal parameter list of a function given that the left
  /// parenthesis is known to exist.
  ///
  /// If `kind == MemberKind.GeneralizedFunctionType`, then names may be
  /// omitted (except for named arguments). Otherwise, types may be omitted.
  Token parseFormalParameters(Token token, MemberKind kind) {
    return parseFormalParametersRest(token.next!, kind);
  }

  /// Parses the formal parameter list of a function given that the left
  /// parenthesis passed in as [token].
  ///
  /// If `kind == MemberKind.GeneralizedFunctionType`, then names may be
  /// omitted (except for named arguments). Otherwise, types may be omitted.
  Token parseFormalParametersRest(Token token, MemberKind kind) {
    Token begin = token;
    assert(optional('(', token));
    listener.beginFormalParameters(begin, kind);
    int parameterCount = 0;
    while (true) {
      Token next = token.next!;
      if (optional(')', next)) {
        token = next;
        break;
      }
      ++parameterCount;
      String? value = next.stringValue;
      if (identical(value, '[')) {
        token = parseOptionalPositionalParameters(token, kind);
        token = ensureCloseParen(token, begin);
        break;
      } else if (identical(value, '{')) {
        token = parseOptionalNamedParameters(token, kind);
        token = ensureCloseParen(token, begin);
        break;
      } else if (identical(value, '[]')) {
        // Recovery
        token = rewriteSquareBrackets(token);
        token = parseOptionalPositionalParameters(token, kind);
        token = ensureCloseParen(token, begin);
        break;
      }
      token = parseFormalParameter(token, FormalParameterKind.mandatory, kind);
      next = token.next!;
      if (!optional(',', next)) {
        Token next = token.next!;
        if (optional(')', next)) {
          token = next;
        } else {
          // Recovery
          if (begin.endGroup!.isSynthetic) {
            // Scanner has already reported a missing `)` error,
            // but placed the `)` in the wrong location, so move it.
            token = rewriter.moveSynthetic(token, begin.endGroup!);
          } else if (next.kind == IDENTIFIER_TOKEN &&
              next.next!.kind == IDENTIFIER_TOKEN) {
            // Looks like a missing comma
            token = rewriteAndRecover(
                token,
                codes.templateExpectedButGot.withArguments(','),
                new SyntheticToken(TokenType.COMMA, next.charOffset));
            continue;
          } else {
            token = ensureCloseParen(token, begin);
          }
        }
        break;
      }
      token = next;
    }
    assert(optional(')', token));
    listener.endFormalParameters(parameterCount, begin, token, kind);
    return token;
  }

  /// Return the message that should be produced when the formal parameters are
  /// missing.
  codes.Message missingParameterMessage(MemberKind kind) {
    if (kind == MemberKind.FunctionTypeAlias) {
      return codes.messageMissingTypedefParameters;
    } else if (kind == MemberKind.NonStaticMethod ||
        kind == MemberKind.StaticMethod) {
      return codes.messageMissingMethodParameters;
    }
    return codes.messageMissingFunctionParameters;
  }

  /// Check if [token] is the usage of 'required' in a formal parameter in a
  /// context where it's not legal (i.e. in non-nnbd-mode).
  bool _isUseOfRequiredInNonNNBD(Token token) {
    if (token.next is StringToken && token.next!.value() == "required") {
      // Possible recovery: Figure out if we're in a situation like
      // required covariant? <type> name
      // (in non-nnbd-mode) where the required modifier is not legal and thus
      // would normally be parsed as the type.
      token = token.next!;
      Token next = token.next!;
      // Skip modifiers.
      while (next.isModifier) {
        token = next;
        next = next.next!;
      }
      // Parse the (potential) new type.
      TypeInfo typeInfoAlternative = computeType(
          token,
          /* required = */ false,
          /* inDeclaration = */ true);
      token = typeInfoAlternative.skipType(token);
      next = token.next!;

      // We've essentially ignored the 'required' at this point.
      // `token` is (in the good state) the last token of the type,
      // `next` is (in the good state) the name;
      // Are we in a 'good' state?
      if (typeInfoAlternative != noType &&
          next.isIdentifier &&
          (optional(',', next.next!) || optional('}', next.next!))) {
        return true;
      }
    }
    return false;
  }

  /// ```
  /// normalFormalParameter:
  ///   functionFormalParameter |
  ///   fieldFormalParameter |
  ///   simpleFormalParameter
  /// ;
  ///
  /// functionFormalParameter:
  ///   metadata 'covariant'? returnType? identifier formalParameterList
  /// ;
  ///
  /// simpleFormalParameter:
  ///   metadata 'covariant'? finalConstVarOrType? identifier |
  /// ;
  ///
  /// fieldFormalParameter:
  ///   metadata finalConstVarOrType? 'this' '.' identifier formalParameterList?
  /// ;
  /// ```
  Token parseFormalParameter(
      Token token, FormalParameterKind parameterKind, MemberKind memberKind) {
    // ignore: unnecessary_null_comparison
    assert(parameterKind != null);
    token = parseMetadataStar(token);

    Token? skippedNonRequiredRequired;
    if (_isUseOfRequiredInNonNNBD(token)) {
      skippedNonRequiredRequired = token.next!;
      reportRecoverableErrorWithToken(skippedNonRequiredRequired,
          codes.templateUnexpectedModifierInNonNnbd);
      token = token.next!;
    }

    Token next = token.next!;
    Token start = next;

    final bool inFunctionType =
        memberKind == MemberKind.GeneralizedFunctionType;

    Token? requiredToken;
    Token? covariantToken;
    Token? varFinalOrConst;
    if (isModifier(next)) {
      if (optional('required', next)) {
        if (parameterKind == FormalParameterKind.optionalNamed) {
          requiredToken = token = next;
          next = token.next!;
        }
      }

      if (isModifier(next)) {
        if (optional('covariant', next)) {
          if (memberKind != MemberKind.StaticMethod &&
              memberKind != MemberKind.TopLevelMethod &&
              memberKind != MemberKind.ExtensionNonStaticMethod &&
              memberKind != MemberKind.ExtensionStaticMethod) {
            covariantToken = token = next;
            next = token.next!;
          }
        }

        if (isModifier(next)) {
          if (!inFunctionType) {
            if (optional('var', next)) {
              varFinalOrConst = token = next;
              next = token.next!;
            } else if (optional('final', next)) {
              varFinalOrConst = token = next;
              next = token.next!;
            }
          }

          if (isModifier(next)) {
            // Recovery
            ModifierRecoveryContext context = new ModifierRecoveryContext(this)
              ..covariantToken = covariantToken
              ..requiredToken = requiredToken
              ..varFinalOrConst = varFinalOrConst;

            token = context.parseFormalParameterModifiers(
                token, parameterKind, memberKind);
            next = token.next!;

            covariantToken = context.covariantToken;
            requiredToken = context.requiredToken;
            varFinalOrConst = context.varFinalOrConst;
          }
        }
      }
    }

    if (requiredToken == null) {
      // `required` was used as a modifier in non-nnbd mode. An error has been
      // emitted. Still use it as a required token for the remainder in an
      // attempt to avoid cascading errors (and for passing to the listener).
      requiredToken = skippedNonRequiredRequired;
    }

    listener.beginFormalParameter(
        start, memberKind, requiredToken, covariantToken, varFinalOrConst);

    // Type is required in a generalized function type, but optional otherwise.
    final Token beforeType = token;
    TypeInfo typeInfo = computeType(token, inFunctionType);
    token = typeInfo.skipType(token);
    next = token.next!;
    if (typeInfo == noType &&
        (optional('.', next) ||
            (next.isIdentifier && optional('.', next.next!)))) {
      // Recovery: Malformed type reference.
      typeInfo = computeType(beforeType, /* required = */ true);
      token = typeInfo.skipType(beforeType);
      next = token.next!;
    }

    final bool isNamedParameter =
        parameterKind == FormalParameterKind.optionalNamed;

    Token? thisKeyword;
    Token? periodAfterThis;
    IdentifierContext nameContext =
        IdentifierContext.formalParameterDeclaration;

    if (!inFunctionType && optional('this', next)) {
      thisKeyword = token = next;
      next = token.next!;
      if (!optional('.', next)) {
        // Recover from a missing period by inserting one.
        next = rewriteAndRecover(
            token,
            codes.templateExpectedButGot.withArguments('.'),
            new SyntheticToken(TokenType.PERIOD, next.charOffset));
      }
      periodAfterThis = token = next;
      next = token.next!;
      nameContext = IdentifierContext.fieldInitializer;
    }

    if (next.isIdentifier) {
      token = next;
      next = token.next!;
    }
    Token? beforeInlineFunctionType;
    TypeParamOrArgInfo typeParam = noTypeParamOrArg;
    if (optional("<", next)) {
      typeParam = computeTypeParamOrArg(token);
      if (typeParam != noTypeParamOrArg) {
        Token closer = typeParam.skip(token);
        if (optional("(", closer.next!)) {
          if (varFinalOrConst != null) {
            reportRecoverableError(
                varFinalOrConst, codes.messageFunctionTypedParameterVar);
          }
          beforeInlineFunctionType = token;
          token = closer.next!.endGroup!;
          next = token.next!;
        }
      }
    } else if (optional("(", next)) {
      if (varFinalOrConst != null) {
        reportRecoverableError(
            varFinalOrConst, codes.messageFunctionTypedParameterVar);
      }
      beforeInlineFunctionType = token;
      token = next.endGroup!;
      next = token.next!;
    }
    if (typeInfo != noType &&
        varFinalOrConst != null &&
        optional('var', varFinalOrConst)) {
      reportRecoverableError(varFinalOrConst, codes.messageTypeAfterVar);
    }

    Token? endInlineFunctionType;
    if (beforeInlineFunctionType != null) {
      endInlineFunctionType =
          typeParam.parseVariables(beforeInlineFunctionType, this);
      listener
          .beginFunctionTypedFormalParameter(beforeInlineFunctionType.next!);
      token = typeInfo.parseType(beforeType, this);
      endInlineFunctionType = parseFormalParametersRequiredOpt(
          endInlineFunctionType, MemberKind.FunctionTypedParameter);
      Token? question;
      if (optional('?', endInlineFunctionType.next!)) {
        question = endInlineFunctionType = endInlineFunctionType.next!;
      }
      listener.endFunctionTypedFormalParameter(
          beforeInlineFunctionType, question);

      // Generalized function types don't allow inline function types.
      // The following isn't allowed:
      //    int Function(int bar(String x)).
      if (inFunctionType) {
        reportRecoverableError(beforeInlineFunctionType.next!,
            codes.messageInvalidInlineFunctionType);
      }
    } else if (inFunctionType) {
      token = typeInfo.ensureTypeOrVoid(beforeType, this);
    } else {
      token = typeInfo.parseType(beforeType, this);
    }

    Token nameToken;
    if (periodAfterThis != null) {
      token = periodAfterThis;
    }
    next = token.next!;
    if (inFunctionType &&
        !isNamedParameter &&
        !next.isKeywordOrIdentifier &&
        beforeInlineFunctionType == null) {
      nameToken = token.next!;
      listener.handleNoName(nameToken);
    } else {
      nameToken = token = ensureIdentifier(token, nameContext);
      if (isNamedParameter && nameToken.lexeme.startsWith("_")) {
        reportRecoverableError(nameToken, codes.messagePrivateNamedParameter);
      }
    }
    if (endInlineFunctionType != null) {
      token = endInlineFunctionType;
    }
    next = token.next!;

    String? value = next.stringValue;
    Token? initializerStart, initializerEnd;
    if ((identical('=', value)) || (identical(':', value))) {
      Token equal = next;
      initializerStart = equal.next!;
      listener.beginFormalParameterDefaultValueExpression();
      token = initializerEnd = parseExpression(equal);
      next = token.next!;
      listener.endFormalParameterDefaultValueExpression();
      // TODO(danrubel): Consider removing the last parameter from the
      // handleValuedFormalParameter event... it appears to be unused.
      listener.handleValuedFormalParameter(equal, next);
      if (isMandatoryFormalParameterKind(parameterKind)) {
        reportRecoverableError(
            equal, codes.messageRequiredParameterWithDefault);
      } else if (isOptionalPositionalFormalParameterKind(parameterKind) &&
          identical(':', value)) {
        reportRecoverableError(
            equal, codes.messagePositionalParameterWithEquals);
      } else if (inFunctionType ||
          memberKind == MemberKind.FunctionTypeAlias ||
          memberKind == MemberKind.FunctionTypedParameter) {
        reportRecoverableError(equal, codes.messageFunctionTypeDefaultValue);
      }
    } else {
      listener.handleFormalParameterWithoutValue(next);
    }
    listener.endFormalParameter(thisKeyword, periodAfterThis, nameToken,
        initializerStart, initializerEnd, parameterKind, memberKind);
    return token;
  }

  /// ```
  /// defaultFormalParameter:
  ///   normalFormalParameter ('=' expression)?
  /// ;
  /// ```
  Token parseOptionalPositionalParameters(Token token, MemberKind kind) {
    Token begin = token = token.next!;
    assert(optional('[', token));
    listener.beginOptionalFormalParameters(begin);
    int parameterCount = 0;
    while (true) {
      Token next = token.next!;
      if (optional(']', next)) {
        break;
      }
      token = parseFormalParameter(
          token, FormalParameterKind.optionalPositional, kind);
      next = token.next!;
      ++parameterCount;
      if (!optional(',', next)) {
        if (!optional(']', next)) {
          // Recovery
          reportRecoverableError(
              next, codes.templateExpectedButGot.withArguments(']'));
          // Scanner guarantees a closing bracket.
          next = begin.endGroup!;
          while (token.next != next) {
            token = token.next!;
          }
        }
        break;
      }
      token = next;
    }
    if (parameterCount == 0) {
      rewriteAndRecover(
          token,
          codes.messageEmptyOptionalParameterList,
          new SyntheticStringToken(TokenType.IDENTIFIER, '',
              token.next!.charOffset, /* _length = */ 0));
      token = parseFormalParameter(
          token, FormalParameterKind.optionalPositional, kind);
      ++parameterCount;
    }
    token = token.next!;
    assert(optional(']', token));
    listener.endOptionalFormalParameters(parameterCount, begin, token);
    return token;
  }

  /// ```
  /// defaultNamedParameter:
  ///   normalFormalParameter ('=' expression)? |
  ///   normalFormalParameter (':' expression)?
  /// ;
  /// ```
  Token parseOptionalNamedParameters(Token token, MemberKind kind) {
    Token begin = token = token.next!;
    assert(optional('{', token));
    listener.beginOptionalFormalParameters(begin);
    int parameterCount = 0;
    while (true) {
      Token next = token.next!;
      if (optional('}', next)) {
        break;
      }
      token =
          parseFormalParameter(token, FormalParameterKind.optionalNamed, kind);
      next = token.next!;
      ++parameterCount;
      if (!optional(',', next)) {
        if (!optional('}', next)) {
          // Recovery
          reportRecoverableError(
              next, codes.templateExpectedButGot.withArguments('}'));
          // Scanner guarantees a closing bracket.
          next = begin.endGroup!;
          while (token.next != next) {
            token = token.next!;
          }
        }
        break;
      }
      token = next;
    }
    if (parameterCount == 0) {
      rewriteAndRecover(
          token,
          codes.messageEmptyNamedParameterList,
          new SyntheticStringToken(TokenType.IDENTIFIER, '',
              token.next!.charOffset, /* _length = */ 0));
      token =
          parseFormalParameter(token, FormalParameterKind.optionalNamed, kind);
      ++parameterCount;
    }
    token = token.next!;
    assert(optional('}', token));
    listener.endOptionalFormalParameters(parameterCount, begin, token);
    return token;
  }

  /// ```
  /// qualified:
  ///   identifier qualifiedRest*
  /// ;
  /// ```
  Token parseQualified(Token token, IdentifierContext context,
      IdentifierContext continuationContext) {
    token = ensureIdentifier(token, context);
    while (optional('.', token.next!)) {
      token = parseQualifiedRest(token, continuationContext);
    }
    return token;
  }

  /// ```
  /// qualifiedRestOpt:
  ///   qualifiedRest?
  /// ;
  /// ```
  Token parseQualifiedRestOpt(
      Token token, IdentifierContext continuationContext) {
    if (optional('.', token.next!)) {
      return parseQualifiedRest(token, continuationContext);
    } else {
      return token;
    }
  }

  /// ```
  /// qualifiedRest:
  ///   '.' identifier
  /// ;
  /// ```
  Token parseQualifiedRest(Token token, IdentifierContext context) {
    token = token.next!;
    assert(optional('.', token));
    Token period = token;
    token = ensureIdentifier(token, context);
    listener.handleQualified(period);
    return token;
  }

  Token skipBlock(Token token) {
    // The scanner ensures that `{` always has a closing `}`.
    return ensureBlock(
            token, /* template = */ null, /* missingBlockName = */ null)
        .endGroup!;
  }

  /// ```
  /// enumType:
  ///   metadata 'enum' id '{' metadata id [',' metadata id]* [','] '}'
  /// ;
  /// ```
  Token parseEnum(Token enumKeyword) {
    assert(optional('enum', enumKeyword));
    listener.beginUncategorizedTopLevelDeclaration(enumKeyword);
    listener.beginEnum(enumKeyword);
    Token token =
        ensureIdentifier(enumKeyword, IdentifierContext.enumDeclaration);
    Token leftBrace = token.next!;
    int count = 0;
    if (optional('{', leftBrace)) {
      token = leftBrace;
      while (true) {
        Token next = token.next!;
        if (optional('}', next)) {
          token = next;
          if (count == 0) {
            reportRecoverableError(token, codes.messageEnumDeclarationEmpty);
          }
          break;
        }
        token = parseMetadataStar(token);
        token = ensureIdentifier(token, IdentifierContext.enumValueDeclaration);
        next = token.next!;
        count++;
        if (optional(',', next)) {
          token = next;
        } else if (optional('}', next)) {
          token = next;
          break;
        } else {
          // Recovery
          Token endGroup = leftBrace.endGroup!;
          if (endGroup.isSynthetic) {
            // The scanner did not place the synthetic '}' correctly.
            token = rewriter.moveSynthetic(token, endGroup);
            break;
          } else if (next.isIdentifier) {
            // If the next token is an identifier, assume a missing comma.
            // TODO(danrubel): Consider improved recovery for missing `}`
            // both here and when the scanner inserts a synthetic `}`
            // for situations such as `enum Letter {a, b   Letter e;`.
            reportRecoverableError(
                next, codes.templateExpectedButGot.withArguments(','));
          } else {
            // Otherwise assume a missing `}` and exit the loop
            reportRecoverableError(
                next, codes.templateExpectedButGot.withArguments('}'));
            token = leftBrace.endGroup!;
            break;
          }
        }
      }
    } else {
      // TODO(danrubel): merge this error message with missing class/mixin body
      leftBrace = ensureBlock(
          token, codes.templateExpectedEnumBody, /* missingBlockName = */ null);
      token = leftBrace.endGroup!;
    }
    assert(optional('}', token));
    listener.endEnum(enumKeyword, leftBrace, count);
    return token;
  }

  Token parseClassOrNamedMixinApplication(
      Token? abstractToken, Token classKeyword) {
    assert(optional('class', classKeyword));
    Token begin = abstractToken ?? classKeyword;
    listener.beginClassOrNamedMixinApplicationPrelude(begin);
    Token name = ensureIdentifier(
        classKeyword, IdentifierContext.classOrMixinOrExtensionDeclaration);
    Token token = computeTypeParamOrArg(
            name, /* inDeclaration = */ true, /* allowsVariance = */ true)
        .parseVariables(name, this);
    if (optional('=', token.next!)) {
      listener.beginNamedMixinApplication(begin, abstractToken, name);
      return parseNamedMixinApplication(token, begin, classKeyword);
    } else {
      listener.beginClassDeclaration(begin, abstractToken, name);
      return parseClass(token, begin, classKeyword, name.lexeme);
    }
  }

  Token parseNamedMixinApplication(
      Token token, Token begin, Token classKeyword) {
    Token equals = token = token.next!;
    assert(optional('=', equals));
    token = computeType(token, /* required = */ true)
        .ensureTypeNotVoid(token, this);
    token = parseMixinApplicationRest(token);
    Token? implementsKeyword = null;
    if (optional('implements', token.next!)) {
      implementsKeyword = token.next!;
      token = parseTypeList(implementsKeyword);
    }
    token = ensureSemicolon(token);
    listener.endNamedMixinApplication(
        begin, classKeyword, equals, implementsKeyword, token);
    return token;
  }

  /// Parse the portion of a class declaration (not a mixin application) that
  /// follows the end of the type parameters.
  ///
  /// ```
  /// classDefinition:
  ///   metadata abstract? 'class' identifier typeParameters?
  ///       (superclass mixins?)? interfaces?
  ///       '{' (metadata classMemberDefinition)* '}' |
  ///   metadata abstract? 'class' mixinApplicationClass
  /// ;
  /// ```
  Token parseClass(
      Token token, Token begin, Token classKeyword, String className) {
    Token start = token;
    token = parseClassHeaderOpt(token, begin, classKeyword);
    if (!optional('{', token.next!)) {
      // Recovery
      token = parseClassHeaderRecovery(start, begin, classKeyword);
      ensureBlock(token, /* template = */ null, 'class declaration');
    }
    token = parseClassOrMixinOrExtensionBody(
        token, DeclarationKind.Class, className);
    listener.endClassDeclaration(begin, token);
    return token;
  }

  Token parseClassHeaderOpt(Token token, Token begin, Token classKeyword) {
    token = parseClassExtendsOpt(token);
    token = parseWithClauseOpt(token);
    token = parseClassOrMixinImplementsOpt(token);
    Token? nativeToken;
    if (optional('native', token.next!)) {
      nativeToken = token.next!;
      token = parseNativeClause(token);
    }
    listener.handleClassHeader(begin, classKeyword, nativeToken);
    return token;
  }

  /// Recover given out-of-order clauses in a class header.
  Token parseClassHeaderRecovery(Token token, Token begin, Token classKeyword) {
    final Listener primaryListener = listener;
    final ClassHeaderRecoveryListener recoveryListener =
        new ClassHeaderRecoveryListener();

    // Reparse to determine which clauses have already been parsed
    // but intercept the events so they are not sent to the primary listener.
    listener = recoveryListener;
    token = parseClassHeaderOpt(token, begin, classKeyword);
    bool hasExtends = recoveryListener.extendsKeyword != null;
    bool hasImplements = recoveryListener.implementsKeyword != null;
    bool hasWith = recoveryListener.withKeyword != null;

    // Update the recovery listener to forward subsequent events
    // to the primary listener.
    recoveryListener.listener = primaryListener;

    // Parse additional out-of-order clauses
    Token start;
    do {
      start = token;

      // Check for extraneous token in the middle of a class header.
      token = skipUnexpectedTokenOpt(
          token, const <String>['extends', 'with', 'implements', '{']);

      // During recovery, clauses are parsed in the same order
      // and generate the same events as in the parseClassHeader method above.
      recoveryListener.clear();

      if (token.next!.isKeywordOrIdentifier &&
          const ['extend', 'on'].contains(token.next!.lexeme)) {
        reportRecoverableError(token.next!,
            codes.templateExpectedInstead.withArguments('extends'));
        token = parseClassExtendsSeenExtendsClause(token.next!, token);
      } else {
        token = parseClassExtendsOpt(token);
      }

      if (recoveryListener.extendsKeyword != null) {
        if (hasExtends) {
          reportRecoverableError(
              recoveryListener.extendsKeyword!, codes.messageMultipleExtends);
        } else {
          if (hasWith) {
            reportRecoverableError(recoveryListener.extendsKeyword!,
                codes.messageWithBeforeExtends);
          } else if (hasImplements) {
            reportRecoverableError(recoveryListener.extendsKeyword!,
                codes.messageImplementsBeforeExtends);
          }
          hasExtends = true;
        }
      }

      token = parseWithClauseOpt(token);

      if (recoveryListener.withKeyword != null) {
        if (hasWith) {
          reportRecoverableError(
              recoveryListener.withKeyword!, codes.messageMultipleWith);
        } else {
          if (hasImplements) {
            reportRecoverableError(recoveryListener.withKeyword!,
                codes.messageImplementsBeforeWith);
          }
          hasWith = true;
        }
      }

      token = parseClassOrMixinImplementsOpt(token);

      if (recoveryListener.implementsKeyword != null) {
        if (hasImplements) {
          reportRecoverableError(recoveryListener.implementsKeyword!,
              codes.messageMultipleImplements);
        } else {
          hasImplements = true;
        }
      }

      listener.handleRecoverClassHeader();

      // Exit if a class body is detected, or if no progress has been made
    } while (!optional('{', token.next!) && start != token);

    listener = primaryListener;
    return token;
  }

  Token parseClassExtendsOpt(Token token) {
    // extends <typeNotVoid>
    Token next = token.next!;
    if (optional('extends', next)) {
      token = parseClassExtendsSeenExtendsClause(next, token);
    } else {
      listener.handleNoType(token);
      listener.handleClassExtends(
          /* extendsKeyword = */ null,
          /* typeCount = */ 1);
    }
    return token;
  }

  Token parseClassExtendsSeenExtendsClause(Token extendsKeyword, Token token) {
    Token next = extendsKeyword;
    token =
        computeType(next, /* required = */ true).ensureTypeNotVoid(next, this);
    int count = 1;

    // Error recovery: extends <typeNotVoid>, <typeNotVoid> [...]
    if (optional(',', token.next!)) {
      reportRecoverableError(token.next!, codes.messageMultipleExtends);

      while (optional(',', token.next!)) {
        next = token.next!;
        token = computeType(next, /* required = */ true)
            .ensureTypeNotVoid(next, this);
        count++;
      }
    }

    listener.handleClassExtends(extendsKeyword, count);
    return token;
  }

  /// ```
  /// implementsClause:
  ///   'implements' typeName (',' typeName)*
  /// ;
  /// ```
  Token parseClassOrMixinImplementsOpt(Token token) {
    Token? implementsKeyword;
    int interfacesCount = 0;
    if (optional('implements', token.next!)) {
      implementsKeyword = token.next!;
      do {
        token = computeType(token.next!, /* required = */ true)
            .ensureTypeNotVoid(token.next!, this);
        ++interfacesCount;
      } while (optional(',', token.next!));
    }
    listener.handleClassOrMixinImplements(implementsKeyword, interfacesCount);
    return token;
  }

  /// Parse a mixin declaration.
  ///
  /// ```
  /// mixinDeclaration:
  ///   metadata? 'mixin' [SimpleIdentifier] [TypeParameterList]?
  ///        [OnClause]? [ImplementsClause]? '{' [ClassMember]* '}'
  /// ;
  /// ```
  Token parseMixin(Token mixinKeyword) {
    assert(optional('mixin', mixinKeyword));
    listener.beginClassOrNamedMixinApplicationPrelude(mixinKeyword);
    Token name = ensureIdentifier(
        mixinKeyword, IdentifierContext.classOrMixinOrExtensionDeclaration);
    Token headerStart = computeTypeParamOrArg(
            name, /* inDeclaration = */ true, /* allowsVariance = */ true)
        .parseVariables(name, this);
    listener.beginMixinDeclaration(mixinKeyword, name);
    Token token = parseMixinHeaderOpt(headerStart, mixinKeyword);
    if (!optional('{', token.next!)) {
      // Recovery
      token = parseMixinHeaderRecovery(token, mixinKeyword, headerStart);
      ensureBlock(token, /* template = */ null, 'mixin declaration');
    }
    token = parseClassOrMixinOrExtensionBody(
        token, DeclarationKind.Mixin, name.lexeme);
    listener.endMixinDeclaration(mixinKeyword, token);
    return token;
  }

  Token parseMixinHeaderOpt(Token token, Token mixinKeyword) {
    token = parseMixinOnOpt(token);
    token = parseClassOrMixinImplementsOpt(token);
    listener.handleMixinHeader(mixinKeyword);
    return token;
  }

  Token parseMixinHeaderRecovery(
      Token token, Token mixinKeyword, Token headerStart) {
    final Listener primaryListener = listener;
    final MixinHeaderRecoveryListener recoveryListener =
        new MixinHeaderRecoveryListener();

    // Reparse to determine which clauses have already been parsed
    // but intercept the events so they are not sent to the primary listener.
    listener = recoveryListener;
    token = parseMixinHeaderOpt(headerStart, mixinKeyword);
    bool hasOn = recoveryListener.onKeyword != null;
    bool hasImplements = recoveryListener.implementsKeyword != null;

    // Update the recovery listener to forward subsequent events
    // to the primary listener.
    recoveryListener.listener = primaryListener;

    // Parse additional out-of-order clauses
    Token start;
    do {
      start = token;

      // Check for extraneous token in the middle of a class header.
      token = skipUnexpectedTokenOpt(
          token, const <String>['on', 'implements', '{']);

      // During recovery, clauses are parsed in the same order and
      // generate the same events as in the parseMixinHeaderOpt method above.
      recoveryListener.clear();

      if (token.next!.isKeywordOrIdentifier &&
          const ['extend', 'extends'].contains(token.next!.lexeme)) {
        reportRecoverableError(
            token.next!, codes.templateExpectedInstead.withArguments('on'));
        token = parseMixinOn(token);
      } else {
        token = parseMixinOnOpt(token);
      }

      if (recoveryListener.onKeyword != null) {
        if (hasOn) {
          reportRecoverableError(
              recoveryListener.onKeyword!, codes.messageMultipleOnClauses);
        } else {
          if (hasImplements) {
            reportRecoverableError(
                recoveryListener.onKeyword!, codes.messageImplementsBeforeOn);
          }
          hasOn = true;
        }
      }

      token = parseClassOrMixinImplementsOpt(token);

      if (recoveryListener.implementsKeyword != null) {
        if (hasImplements) {
          reportRecoverableError(recoveryListener.implementsKeyword!,
              codes.messageMultipleImplements);
        } else {
          hasImplements = true;
        }
      }

      listener.handleRecoverMixinHeader();

      // Exit if a mixin body is detected, or if no progress has been made
    } while (!optional('{', token.next!) && start != token);

    listener = primaryListener;
    return token;
  }

  /// ```
  /// onClause:
  ///   'on' typeName (',' typeName)*
  /// ;
  /// ```
  Token parseMixinOnOpt(Token token) {
    if (!optional('on', token.next!)) {
      listener.handleMixinOn(/* onKeyword = */ null, /* typeCount = */ 0);
      return token;
    }
    return parseMixinOn(token);
  }

  Token parseMixinOn(Token token) {
    Token onKeyword = token.next!;
    // During recovery, the [onKeyword] can be "extend" or "extends"
    assert(optional('on', onKeyword) ||
        optional('extends', onKeyword) ||
        onKeyword.lexeme == 'extend');
    int typeCount = 0;
    do {
      token = computeType(token.next!, /* required = */ true)
          .ensureTypeNotVoid(token.next!, this);
      ++typeCount;
    } while (optional(',', token.next!));
    listener.handleMixinOn(onKeyword, typeCount);
    return token;
  }

  /// ```
  /// 'extension' <identifier>? <typeParameters>? 'on' <type> '?'?
  //   `{'
  //     <memberDeclaration>*
  //   `}'
  /// ```
  Token parseExtension(Token extensionKeyword) {
    assert(optional('extension', extensionKeyword));
    Token token = extensionKeyword;
    listener.beginExtensionDeclarationPrelude(extensionKeyword);
    Token? name = token.next!;
    if (name.isIdentifier && !optional('on', name)) {
      token = name;
      if (name.type.isBuiltIn) {
        reportRecoverableErrorWithToken(
            token, codes.templateBuiltInIdentifierInDeclaration);
      }
    } else {
      name = null;
    }
    token = computeTypeParamOrArg(token, /* inDeclaration = */ true)
        .parseVariables(token, this);
    listener.beginExtensionDeclaration(extensionKeyword, name);
    Token onKeyword = token.next!;
    if (!optional('on', onKeyword)) {
      // Recovery
      if (optional('extends', onKeyword) ||
          optional('implements', onKeyword) ||
          optional('with', onKeyword)) {
        reportRecoverableError(
            onKeyword, codes.templateExpectedInstead.withArguments('on'));
      } else {
        reportRecoverableError(
            token, codes.templateExpectedAfterButGot.withArguments('on'));
        onKeyword = rewriter.insertSyntheticKeyword(token, Keyword.ON);
      }
    }
    TypeInfo typeInfo = computeType(onKeyword, /* required = */ true);
    token = typeInfo.ensureTypeOrVoid(onKeyword, this);
    if (!optional('{', token.next!)) {
      // Recovery
      Token next = token.next!;
      while (!next.isEof) {
        if (optional(',', next) ||
            optional('extends', next) ||
            optional('implements', next) ||
            optional('on', next) ||
            optional('with', next)) {
          // Report an error and skip `,` or specific keyword
          // optionally followed by an identifier
          reportRecoverableErrorWithToken(next, codes.templateUnexpectedToken);
          token = next;
          next = token.next!;
          if (next.isIdentifier) {
            token = next;
            next = token.next!;
          }
        } else {
          break;
        }
      }
      ensureBlock(token, /* template = */ null, 'extension declaration');
    }
    token = parseClassOrMixinOrExtensionBody(
        token, DeclarationKind.Extension, name?.lexeme);
    listener.endExtensionDeclaration(extensionKeyword, onKeyword, token);
    return token;
  }

  Token parseStringPart(Token token) {
    Token next = token.next!;
    if (next.kind != STRING_TOKEN) {
      reportRecoverableErrorWithToken(next, codes.templateExpectedString);
      next = rewriter.insertToken(token,
          new SyntheticStringToken(TokenType.STRING, '', next.charOffset));
    }
    listener.handleStringPart(next);
    return next;
  }

  /// Insert a synthetic identifier after the given [token] and create an error
  /// message based on the given [context]. Return the synthetic identifier that
  /// was inserted.
  Token insertSyntheticIdentifier(Token token, IdentifierContext context,
      {codes.Message? message, Token? messageOnToken}) {
    Token next = token.next!;
    reportRecoverableError(messageOnToken ?? next,
        message ?? context.recoveryTemplate.withArguments(next));
    return rewriter.insertSyntheticIdentifier(token);
  }

  /// Parse a simple identifier at the given [token], and return the identifier
  /// that was parsed.
  ///
  /// If the token is not an identifier, or is not appropriate for use as an
  /// identifier in the given [context], create a synthetic identifier, report
  /// an error, and return the synthetic identifier.
  Token ensureIdentifier(Token token, IdentifierContext context) {
    // ignore: unnecessary_null_comparison
    assert(context != null);
    Token identifier = token.next!;
    if (identifier.kind != IDENTIFIER_TOKEN) {
      identifier = context.ensureIdentifier(token, this);
      // ignore: unnecessary_null_comparison
      assert(identifier != null);
      assert(identifier.isKeywordOrIdentifier);
    }
    listener.handleIdentifier(identifier, context);
    return identifier;
  }

  /// Parse a simple identifier at the given [token], and return the identifier
  /// that was parsed.
  ///
  /// If the token is not an identifier, or is not appropriate for use as an
  /// identifier in the given [context], create a synthetic identifier, report
  /// an error, and return the synthetic identifier.
  /// [isRecovered] is passed to [context] which - if true - allows implementers
  /// to use the token as an identifier, even if it isn't a valid identifier.
  Token ensureIdentifierPotentiallyRecovered(
      Token token, IdentifierContext context, bool isRecovered) {
    // ignore: unnecessary_null_comparison
    assert(context != null);
    Token identifier = token.next!;
    if (identifier.kind != IDENTIFIER_TOKEN) {
      identifier = context.ensureIdentifierPotentiallyRecovered(
          token, this, isRecovered);
      // ignore: unnecessary_null_comparison
      assert(identifier != null);
      assert(identifier.isKeywordOrIdentifier);
    }
    listener.handleIdentifier(identifier, context);
    return identifier;
  }

  bool notEofOrValue(String value, Token token) {
    return !identical(token.kind, EOF_TOKEN) &&
        !identical(value, token.stringValue);
  }

  Token parseTypeVariablesOpt(Token token) {
    return computeTypeParamOrArg(token, /* inDeclaration = */ true)
        .parseVariables(token, this);
  }

  /// Parse a top level field or function.
  ///
  /// This method is only invoked from outside the parser. As a result, this
  /// method takes the next token to be consumed rather than the last consumed
  /// token and returns the token after the last consumed token rather than the
  /// last consumed token.
  Token parseTopLevelMember(Token token) {
    token = parseMetadataStar(syntheticPreviousToken(token));
    return parseTopLevelMemberImpl(token).next!;
  }

  /// Check if [token] is the usage of 'late' before a field declaration in a
  /// context where it's not legal (i.e. in non-nnbd-mode).
  bool _isUseOfLateInNonNNBD(Token token) {
    if (token is StringToken && token.value() == "late") {
      // Possible recovery: Figure out if we're in a situation like
      // late final? <type>/var/const name [...]
      // (in non-nnbd-mode) where the late modifier is not legal and thus would
      // normally be parsed as the type.
      Token next = token.next!;
      // Skip modifiers.
      while (next.isModifier) {
        token = next;
        next = next.next!;
      }
      // Parse the (potential) new type.
      TypeInfo typeInfoAlternative = computeType(
          token,
          /* required = */ false,
          /* inDeclaration = */ true);
      token = typeInfoAlternative.skipType(token);
      next = token.next!;

      // We've essentially ignored the 'late' at this point.
      // `token` is (in the good state) the last token of the type,
      // `next` is (in the good state) the name;
      // Are we in a 'good' state?
      if (typeInfoAlternative != noType &&
          next.isIdentifier &&
          indicatesMethodOrField(next.next!)) {
        return true;
      }
    }
    return false;
  }

  Token parseTopLevelMemberImpl(Token token) {
    Token beforeStart = token;
    Token next = token.next!;
    listener.beginTopLevelMember(next);

    Token? skippedNonLateLate;

    if (_isUseOfLateInNonNNBD(next)) {
      skippedNonLateLate = next;
      reportRecoverableErrorWithToken(
          skippedNonLateLate, codes.templateUnexpectedModifierInNonNnbd);
      token = token.next!;
      beforeStart = token;
      next = token.next!;
    }

    Token? externalToken;
    Token? lateToken;
    Token? varFinalOrConst;

    if (isModifier(next)) {
      if (optional('external', next)) {
        externalToken = token = next;
        next = token.next!;
      }
      if (isModifier(next)) {
        if (optional('final', next)) {
          varFinalOrConst = token = next;
          next = token.next!;
        } else if (optional('var', next)) {
          varFinalOrConst = token = next;
          next = token.next!;
        } else if (optional('const', next)) {
          varFinalOrConst = token = next;
          next = token.next!;
        } else if (optional('late', next)) {
          lateToken = token = next;
          next = token.next!;
          if (isModifier(next) && optional('final', next)) {
            varFinalOrConst = token = next;
            next = token.next!;
          }
        }
        if (isModifier(next)) {
          // Recovery
          if (varFinalOrConst != null &&
              (optional('final', next) ||
                  optional('var', next) ||
                  optional('const', next))) {
            // If another `var`, `final`, or `const` then fall through
            // to parse that as part of the next top level declaration.
          } else {
            ModifierRecoveryContext context = new ModifierRecoveryContext(this)
              ..externalToken = externalToken
              ..lateToken = lateToken
              ..varFinalOrConst = varFinalOrConst;

            token = context.parseTopLevelModifiers(token);
            next = token.next!;

            externalToken = context.externalToken;
            lateToken = context.lateToken;
            varFinalOrConst = context.varFinalOrConst;
          }
        }
      }
    }
    if (lateToken == null) {
      // `late` was used as a modifier in non-nnbd mode. An error has been
      // emitted. Still use it as a late token for the remainder in an attempt
      // to avoid cascading errors (and for passing to the listener).
      lateToken = skippedNonLateLate;
    }

    Token beforeType = token;
    TypeInfo typeInfo =
        computeType(token, /* required = */ false, /* inDeclaration = */ true);
    token = typeInfo.skipType(token);
    next = token.next!;

    Token? getOrSet;
    String? value = next.stringValue;
    if (identical(value, 'get') || identical(value, 'set')) {
      if (next.next!.isIdentifier) {
        getOrSet = token = next;
        next = token.next!;
      }
    }

    bool nameIsRecovered = false;

    // Recovery: If the code is
    // <return type>? <reserved word> <token indicating method or field>
    // take the reserved keyword as the name.
    if (typeInfo == noType &&
        varFinalOrConst == null &&
        isReservedKeyword(next.next!) &&
        indicatesMethodOrField(next.next!.next!)) {
      // Recovery: Use the reserved keyword despite that not being legal.
      typeInfo = computeType(
          token,
          /*required = */ true,
          /* inDeclaration = */ true);
      token = typeInfo.skipType(token);
      next = token.next!;
      nameIsRecovered = true;
    }

    if (next.type != TokenType.IDENTIFIER) {
      value = next.stringValue;
      if (identical(value, 'factory') || identical(value, 'operator')) {
        // `factory` and `operator` can be used as an identifier.
        value = next.next!.stringValue;
        if (getOrSet == null &&
            !identical(value, '(') &&
            !identical(value, '{') &&
            !identical(value, '<') &&
            !identical(value, '=>') &&
            !identical(value, '=') &&
            !identical(value, ';') &&
            !identical(value, ',')) {
          // Recovery
          value = next.stringValue;
          if (identical(value, 'factory')) {
            reportRecoverableError(
                next, codes.messageFactoryTopLevelDeclaration);
          } else {
            reportRecoverableError(next, codes.messageTopLevelOperator);
            if (next.next!.isOperator) {
              token = next;
              next = token.next!;
              if (optional('(', next.next!)) {
                rewriter.insertSyntheticIdentifier(
                    next, '#synthetic_identifier_${next.charOffset}');
              }
            }
          }
          listener.handleInvalidTopLevelDeclaration(next);
          return next;
        }
        // Fall through and continue parsing
      } else if (!next.isIdentifier) {
        // Recovery
        if (next.isKeyword) {
          // Fall through to parse the keyword as the identifier.
          // ensureIdentifier will report the error.
        } else if (token == beforeStart) {
          // Ensure we make progress.
          return parseInvalidTopLevelDeclaration(token);
        } else {
          // Looks like a declaration missing an identifier.
          // Insert synthetic identifier and fall through.
          insertSyntheticIdentifier(token, IdentifierContext.methodDeclaration);
          next = token.next!;
        }
      }
    }
    // At this point, `token` is beforeName.

    // Recovery: Inserted ! after method name.
    if (optional('!', next.next!)) {
      next = next.next!;
    }

    next = next.next!;
    value = next.stringValue;
    if (getOrSet != null ||
        identical(value, '(') ||
        identical(value, '{') ||
        identical(value, '<') ||
        identical(value, '.') ||
        identical(value, '=>')) {
      if (varFinalOrConst != null) {
        if (optional('var', varFinalOrConst)) {
          reportRecoverableError(varFinalOrConst, codes.messageVarReturnType);
        } else {
          reportRecoverableErrorWithToken(
              varFinalOrConst, codes.templateExtraneousModifier);
        }
      } else if (lateToken != null) {
        reportRecoverableErrorWithToken(
            lateToken, codes.templateExtraneousModifier);
      }
      return parseTopLevelMethod(beforeStart, externalToken, beforeType,
          typeInfo, getOrSet, token.next!, nameIsRecovered);
    }

    if (getOrSet != null) {
      reportRecoverableErrorWithToken(
          getOrSet, codes.templateExtraneousModifier);
    }
    return parseFields(
        beforeStart,
        /* abstractToken = */ null,
        externalToken,
        /* staticToken = */ null,
        /* covariantToken = */ null,
        lateToken,
        varFinalOrConst,
        beforeType,
        typeInfo,
        token.next!,
        DeclarationKind.TopLevel,
        /* enclosingDeclarationName = */ null,
        nameIsRecovered);
  }

  Token parseFields(
      Token beforeStart,
      Token? abstractToken,
      Token? externalToken,
      Token? staticToken,
      Token? covariantToken,
      Token? lateToken,
      Token? varFinalOrConst,
      Token beforeType,
      TypeInfo typeInfo,
      Token name,
      DeclarationKind kind,
      String? enclosingDeclarationName,
      bool nameIsRecovered) {
    listener.beginFields(beforeStart);

    // Covariant affects only the setter and final fields do not have a setter,
    // unless it's a late field (dartbug.com/40805).
    // Field that are covariant late final with initializers are checked further
    // down.
    if (covariantToken != null && lateToken == null) {
      if (varFinalOrConst != null && optional('final', varFinalOrConst)) {
        reportRecoverableError(covariantToken, codes.messageFinalAndCovariant);
        covariantToken = null;
      }
    }
    if (typeInfo == noType) {
      if (varFinalOrConst == null) {
        reportRecoverableError(name, codes.messageMissingConstFinalVarOrType);
      }
    } else {
      if (varFinalOrConst != null && optional('var', varFinalOrConst)) {
        reportRecoverableError(varFinalOrConst, codes.messageTypeAfterVar);
      }
    }
    if (abstractToken != null && externalToken != null) {
      reportRecoverableError(abstractToken, codes.messageAbstractExternalField);
    }

    Token token = typeInfo.parseType(beforeType, this);
    assert(token.next == name || token.next!.isEof);

    IdentifierContext context = kind == DeclarationKind.TopLevel
        ? IdentifierContext.topLevelVariableDeclaration
        : IdentifierContext.fieldDeclaration;
    Token firstName = name = ensureIdentifierPotentiallyRecovered(
        token, context, /* isRecovered = */ nameIsRecovered);

    // Check for covariant late final with initializer.
    if (covariantToken != null && lateToken != null) {
      if (varFinalOrConst != null && optional('final', varFinalOrConst)) {
        Token next = name.next!;
        if (optional('=', next)) {
          reportRecoverableError(covariantToken,
              codes.messageFinalAndCovariantLateWithInitializer);
          covariantToken = null;
        }
      }
    }

    int fieldCount = 1;
    token = parseFieldInitializerOpt(name, name, lateToken, abstractToken,
        externalToken, varFinalOrConst, kind, enclosingDeclarationName);
    while (optional(',', token.next!)) {
      name = ensureIdentifier(token.next!, context);
      token = parseFieldInitializerOpt(name, name, lateToken, abstractToken,
          externalToken, varFinalOrConst, kind, enclosingDeclarationName);
      ++fieldCount;
    }
    Token semicolon = token.next!;
    if (optional(';', semicolon)) {
      token = semicolon;
    } else {
      // Recovery
      if (kind == DeclarationKind.TopLevel &&
          beforeType.next!.isIdentifier &&
          beforeType.next!.lexeme == 'extension') {
        // Looks like an extension method
        // TODO(danrubel): Remove when extension methods are enabled by default
        // because then 'extension' will be interpreted as a built-in
        // and this code will never be executed
        reportRecoverableError(
            beforeType.next!,
            codes.templateExperimentNotEnabled
                .withArguments('extension-methods', '2.6'));
        token = rewriter.insertSyntheticToken(token, TokenType.SEMICOLON);
      } else {
        token = ensureSemicolon(token);
      }
    }
    switch (kind) {
      case DeclarationKind.TopLevel:
        assert(abstractToken == null);
        listener.endTopLevelFields(externalToken, staticToken, covariantToken,
            lateToken, varFinalOrConst, fieldCount, beforeStart.next!, token);
        break;
      case DeclarationKind.Class:
        listener.endClassFields(
            abstractToken,
            externalToken,
            staticToken,
            covariantToken,
            lateToken,
            varFinalOrConst,
            fieldCount,
            beforeStart.next!,
            token);
        break;
      case DeclarationKind.Mixin:
        listener.endMixinFields(
            abstractToken,
            externalToken,
            staticToken,
            covariantToken,
            lateToken,
            varFinalOrConst,
            fieldCount,
            beforeStart.next!,
            token);
        break;
      case DeclarationKind.Extension:
        if (abstractToken != null) {
          reportRecoverableError(
              firstName, codes.messageAbstractExtensionField);
        }
        if (staticToken == null && externalToken == null) {
          reportRecoverableError(
              firstName, codes.messageExtensionDeclaresInstanceField);
        }
        listener.endExtensionFields(
            abstractToken,
            externalToken,
            staticToken,
            covariantToken,
            lateToken,
            varFinalOrConst,
            fieldCount,
            beforeStart.next!,
            token);
        break;
    }
    return token;
  }

  Token parseTopLevelMethod(
      Token beforeStart,
      Token? externalToken,
      Token beforeType,
      TypeInfo typeInfo,
      Token? getOrSet,
      Token name,
      bool nameIsRecovered) {
    listener.beginTopLevelMethod(beforeStart, externalToken);

    Token token = typeInfo.parseType(beforeType, this);
    assert(token.next == (getOrSet ?? name) || token.next!.isEof);
    name = ensureIdentifierPotentiallyRecovered(
        getOrSet ?? token,
        IdentifierContext.topLevelFunctionDeclaration,
        /* isRecovered = */ nameIsRecovered);

    bool isGetter = false;
    if (getOrSet == null) {
      token = parseMethodTypeVar(name);
    } else {
      isGetter = optional("get", getOrSet);
      token = name;
      listener.handleNoTypeVariables(token.next!);
    }
    token = parseGetterOrFormalParameters(
        token, name, isGetter, MemberKind.TopLevelMethod);
    AsyncModifier savedAsyncModifier = asyncState;
    Token asyncToken = token.next!;
    token = parseAsyncModifierOpt(token);
    if (getOrSet != null && !inPlainSync && optional("set", getOrSet)) {
      reportRecoverableError(asyncToken, codes.messageSetterNotSync);
    }
    // TODO(paulberry): code below is slightly hacky to allow for implementing
    // the feature "Infer non-nullability from local boolean variables"
    // (https://github.com/dart-lang/language/issues/1274).  Since the version
    // of Dart that is used for presubmit checks lags slightly behind master,
    // we need the code to analyze correctly regardless of whether local boolean
    // variables cause promotion or not.  Once the version of dart used for
    // presubmit checks has been updated, this can be cleaned up to:
    //   bool isExternal = externalToken != null;
    //   if (externalToken != null && !optional(';', token.next!)) {
    //     reportRecoverableError(
    //         externalToken, codes.messageExternalMethodWithBody);
    //   }
    bool isExternal = false;
    if (externalToken != null) {
      isExternal = true;
      if (!optional(';', token.next!)) {
        reportRecoverableError(
            externalToken, codes.messageExternalMethodWithBody);
      }
    }
    token = parseFunctionBody(
        token, /* ofFunctionExpression = */ false, isExternal);
    asyncState = savedAsyncModifier;
    listener.endTopLevelMethod(beforeStart.next!, getOrSet, token);
    return token;
  }

  Token parseMethodTypeVar(Token name) {
    if (optional('!', name.next!)) {
      // Recovery
      name = name.next!;
      reportRecoverableErrorWithToken(name, codes.templateUnexpectedToken);
    }
    if (!optional('<', name.next!)) {
      return noTypeParamOrArg.parseVariables(name, this);
    }
    TypeParamOrArgInfo typeVar =
        computeTypeParamOrArg(name, /* inDeclaration = */ true);
    Token token = typeVar.parseVariables(name, this);
    if (optional('=', token.next!)) {
      // Recovery
      token = token.next!;
      reportRecoverableErrorWithToken(token, codes.templateUnexpectedToken);
    }
    return token;
  }

  Token parseFieldInitializerOpt(
      Token token,
      Token name,
      Token? lateToken,
      Token? abstractToken,
      Token? externalToken,
      Token? varFinalOrConst,
      DeclarationKind kind,
      String? enclosingDeclarationName) {
    if (name.lexeme == enclosingDeclarationName) {
      reportRecoverableError(name, codes.messageMemberWithSameNameAsClass);
    }
    Token next = token.next!;
    if (optional('=', next)) {
      Token assignment = next;
      listener.beginFieldInitializer(next);
      token = parseExpression(next);
      listener.endFieldInitializer(assignment, token.next!);
    } else {
      if (varFinalOrConst != null && !name.isSynthetic) {
        if (optional("const", varFinalOrConst)) {
          reportRecoverableError(
              name,
              codes.templateConstFieldWithoutInitializer
                  .withArguments(name.lexeme));
        } else if (kind == DeclarationKind.TopLevel &&
            optional("final", varFinalOrConst) &&
            lateToken == null &&
            abstractToken == null &&
            externalToken == null) {
          reportRecoverableError(
              name,
              codes.templateFinalFieldWithoutInitializer
                  .withArguments(name.lexeme));
        }
      }
      listener.handleNoFieldInitializer(token.next!);
    }
    return token;
  }

  Token parseVariableInitializerOpt(Token token) {
    if (optional('=', token.next!)) {
      Token assignment = token.next!;
      listener.beginVariableInitializer(assignment);
      token = parseExpression(assignment);
      listener.endVariableInitializer(assignment);
    } else {
      listener.handleNoVariableInitializer(token);
    }
    return token;
  }

  Token parseInitializersOpt(Token token) {
    if (optional(':', token.next!)) {
      return parseInitializers(token.next!);
    } else {
      listener.handleNoInitializers();
      return token;
    }
  }

  /// ```
  /// initializers:
  ///   ':' initializerListEntry (',' initializerListEntry)*
  /// ;
  /// ```
  Token parseInitializers(Token token) {
    Token begin = token;
    assert(optional(':', begin));
    listener.beginInitializers(begin);
    int count = 0;
    bool old = mayParseFunctionExpressions;
    mayParseFunctionExpressions = false;
    Token next = begin;
    while (true) {
      token = parseInitializer(next);
      ++count;
      next = token.next!;
      if (!optional(',', next)) {
        // Recovery: Found an identifier which could be
        // 1) missing preceding `,` thus it's another initializer, or
        // 2) missing preceding `;` thus it's a class member, or
        // 3) missing preceding '{' thus it's a statement
        if (optional('assert', next)) {
          next = next.next!;
          if (!optional('(', next)) {
            break;
          }
          // Looks like assert expression ... fall through to insert comma
        } else if (!next.isIdentifier && !optional('this', next)) {
          // An identifier that wasn't an initializer. Break.
          break;
        } else {
          if (optional('this', next)) {
            next = next.next!;
            if (!optional('.', next)) {
              break;
            }
            next = next.next!;
            if (!next.isIdentifier && !optional('assert', next)) {
              break;
            }
          }
          next = next.next!;
          if (!optional('=', next)) {
            break;
          }
          // Looks like field assignment... fall through to insert comma
        }
        // TODO(danrubel): Consider enhancing this to indicate that we are
        // expecting one of `,` or `;` or `{`
        reportRecoverableError(
            token, codes.templateExpectedAfterButGot.withArguments(','));
        next = rewriter.insertSyntheticToken(token, TokenType.COMMA);
      }
    }
    mayParseFunctionExpressions = old;
    listener.endInitializers(count, begin, token.next!);
    return token;
  }

  /// ```