// 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 fasta.parser.listener;

import '../../scanner/token.dart' show Token;

import '../fasta_codes.dart' show Message;

import '../quote.dart' show UnescapeErrorListener;

import 'assert.dart' show Assert;

import 'formal_parameter_kind.dart' show FormalParameterKind;

import 'identifier_context.dart' show IdentifierContext;

import 'member_kind.dart' show MemberKind;

/// A parser event listener that does nothing except throw exceptions
/// on parser errors.
///
/// Events are methods that begin with one of: `begin`, `end`, or `handle`.
///
/// Events starting with `begin` and `end` come in pairs. Normally, a
/// `beginFoo` event is followed by an `endFoo` event. There's a few exceptions
/// documented below.
///
/// Events starting with `handle` are used when isn't possible to have a begin
/// event.
class Listener implements UnescapeErrorListener {
  Uri get uri => null;

  void logEvent(String name) {}

  set suppressParseErrors(bool value) {}

  void beginArguments(Token token) {}

  void endArguments(int count, Token beginToken, Token endToken) {
    logEvent("Arguments");
  }

  /// Handle async modifiers `async`, `async*`, `sync`.
  void handleAsyncModifier(Token asyncToken, Token starToken) {
    logEvent("AsyncModifier");
  }

  void beginAwaitExpression(Token token) {}

  void endAwaitExpression(Token beginToken, Token endToken) {
    logEvent("AwaitExpression");
  }

  void beginBlock(Token token) {}

  void endBlock(int count, Token beginToken, Token endToken) {
    logEvent("Block");
  }

  /// Called to handle a block that has been parsed but is not associated
  /// with any top level function declaration. Substructures:
  /// - block
  void handleInvalidTopLevelBlock(Token token) {}

  void beginCascade(Token token) {}

  void endCascade() {
    logEvent("Cascade");
  }

  void beginCaseExpression(Token caseKeyword) {}

  void endCaseExpression(Token colon) {
    logEvent("CaseExpression");
  }

  void beginClassOrMixinBody(Token token) {}

  /// Handle the end of the body of a class or mixin declaration.
  /// The only substructures are the class or mixin members.
  void endClassOrMixinBody(int memberCount, Token beginToken, Token endToken) {
    logEvent("ClassOrMixinBody");
  }

  /// Called before parsing a class or named mixin application.
  void beginClassOrNamedMixinApplication(Token token) {}

  /// Handle the beginning of a class declaration.
  /// [begin] may be the same as [name], or may point to modifiers
  /// (or extraneous modifiers in the case of recovery) preceding [name].
  void beginClassDeclaration(Token begin, Token abstractToken, Token name) {}

  /// Handle an extends clause in a class declaration. Substructures:
  /// - supertype (may be a mixin application)
  void handleClassExtends(Token extendsKeyword) {
    logEvent("ClassExtends");
  }

  /// Handle an implements clause in a class or mixin declaration.
  /// Substructures:
  /// - implemented types
  void handleClassOrMixinImplements(
      Token implementsKeyword, int interfacesCount) {
    logEvent("ClassImplements");
  }

  /// Handle the header of a class declaration.  Substructures:
  /// - metadata
  /// - modifiers
  /// - class name
  /// - type variables
  /// - supertype (may be a mixin application)
  /// - implemented types
  /// - native clause
  void handleClassHeader(Token begin, Token classKeyword, Token nativeToken) {
    logEvent("ClassHeader");
  }

  /// Handle recovery associated with a class header.
  /// This may be called multiple times after [handleClassHeader]
  /// to recover information about the previous class header.
  /// The substructures are a subset of
  /// and in the same order as [handleClassHeader]:
  /// - supertype (may be a mixin application)
  /// - implemented types
  void handleRecoverClassHeader() {
    logEvent("RecoverClassHeader");
  }

  /// Handle the end of a class declaration.  Substructures:
  /// - class header
  /// - class body
  void endClassDeclaration(Token beginToken, Token endToken) {
    logEvent("ClassDeclaration");
  }

  /// Handle the beginning of a mixin declaration.
  void beginMixinDeclaration(Token mixinKeyword, Token name) {}

  /// Handle an on clause in a mixin declaration. Substructures:
  /// - implemented types
  void handleMixinOn(Token onKeyword, int typeCount) {
    logEvent("MixinOn");
  }

  /// Handle the header of a class declaration.  Substructures:
  /// - metadata
  /// - mixin name
  /// - type variables
  /// - on types
  /// - implemented types
  void handleMixinHeader(Token mixinKeyword) {
    logEvent("MixinHeader");
  }

  /// Handle the end of a mixin declaration.  Substructures:
  /// - mixin header
  /// - class or mixin body
  void endMixinDeclaration(Token token) {
    logEvent("MixinDeclaration");
  }

  void beginCombinators(Token token) {}

  void endCombinators(int count) {
    logEvent("Combinators");
  }

  void beginCompilationUnit(Token token) {}

  /// This method exists for analyzer compatibility only
  /// and will be removed once analyzer/fasta integration is complete.
  ///
  /// This is called when [parseDirectives] has parsed all directives
  /// and is skipping the remainder of the file.  Substructures:
  /// - metadata
  void handleDirectivesOnly() {}

  void endCompilationUnit(int count, Token token) {
    logEvent("CompilationUnit");
  }

  void beginConstLiteral(Token token) {}

  void endConstLiteral(Token token) {
    logEvent("ConstLiteral");
  }

  void beginConstructorReference(Token start) {}

  void endConstructorReference(
      Token start, Token periodBeforeName, Token endToken) {
    logEvent("ConstructorReference");
  }

  void beginDoWhileStatement(Token token) {}

  void endDoWhileStatement(
      Token doKeyword, Token whileKeyword, Token endToken) {
    logEvent("DoWhileStatement");
  }

  void beginDoWhileStatementBody(Token token) {}

  void endDoWhileStatementBody(Token token) {
    logEvent("DoWhileStatementBody");
  }

  void beginWhileStatementBody(Token token) {}

  void endWhileStatementBody(Token token) {
    logEvent("WhileStatementBody");
  }

  void beginEnum(Token enumKeyword) {}

  /// Handle the end of an enum declaration.  Substructures:
  /// - Metadata
  /// - Enum name (identifier)
  /// - [count] times:
  ///   - Enum value (identifier)
  void endEnum(Token enumKeyword, Token leftBrace, int count) {
    logEvent("Enum");
  }

  void beginExport(Token token) {}

  /// Handle the end of an export directive.  Substructures:
  /// - metadata
  /// - uri
  /// - conditional uris
  /// - combinators
  void endExport(Token exportKeyword, Token semicolon) {
    logEvent("Export");
  }

  void beginExpressionStatement(Token token) {}

  /// Called by [Parser] after parsing an extraneous expression as error
  /// recovery. For a stack-based listener, the suggested action is to discard
  /// an expression from the stack.
  void handleExtraneousExpression(Token token, Message message) {
    logEvent("ExtraneousExpression");
  }

  void endExpressionStatement(Token token) {
    logEvent("ExpressionStatement");
  }

  void beginFactoryMethod(
      Token lastConsumed, Token externalToken, Token constToken) {}

  void endFactoryMethod(
      Token beginToken, Token factoryKeyword, Token endToken) {
    logEvent("FactoryMethod");
  }

  /// [beginToken] is the first token of the parameter, e.g. `int` in
  /// `int a`, or `this` in `C(this.f)`.
  void beginFormalParameter(Token beginToken, MemberKind kind,
      Token covariantToken, Token varFinalOrConst) {}

  /// [endToken] is the last token of the parameter, e.g. `1` in `{int a = 1}`.
  void endFormalParameter(
      Token thisKeyword,
      Token periodAfterThis,
      Token nameToken,
      FormalParameterKind kind,
      MemberKind memberKind,
      Token endToken) {
    logEvent("FormalParameter");
  }

  void handleNoFormalParameters(Token token, MemberKind kind) {
    logEvent("NoFormalParameters");
  }

  void beginFormalParameters(Token token, MemberKind kind) {}

  void endFormalParameters(
      int count, Token beginToken, Token endToken, MemberKind kind) {
    logEvent("FormalParameters");
  }

  /// Handle the end of a field declaration.  Substructures:
  /// - Metadata
  /// - Modifiers
  /// - Type
  /// - Variable declarations (count times)
  ///
  /// Doesn't have a corresponding begin event, use [beginMember] instead.
  void endFields(Token staticToken, Token covariantToken, Token varFinalOrConst,
      int count, Token beginToken, Token endToken) {
    logEvent("Fields");
  }

  /// Marks the start of a for statement which is ended by either
  /// [endForStatement] or [endForIn].
  void beginForStatement(Token token) {}

  void endForStatement(Token forKeyword, Token leftParen, Token leftSeparator,
      int updateExpressionCount, Token endToken) {
    logEvent("ForStatement");
  }

  void beginForStatementBody(Token token) {}

  void endForStatementBody(Token token) {
    logEvent("ForStatementBody");
  }

  // One of the two possible corresponding end events for [beginForStatement].
  void endForIn(Token awaitToken, Token forToken, Token leftParenthesis,
      Token inKeyword, Token endToken) {
    logEvent("ForIn");
  }

  void beginForInExpression(Token token) {}

  void endForInExpression(Token token) {
    logEvent("ForInExpression");
  }

  void beginForInBody(Token token) {}

  void endForInBody(Token token) {
    logEvent("ForInBody");
  }

  /// Handle the beginning of a named function expression which isn't legal
  /// syntax in Dart.  Useful for recovering from Javascript code being pasted
  /// into a Dart proram, as it will interpret `function foo() {}` as a named
  /// function expression with return type `function` and name `foo`.
  ///
  /// Substructures:
  /// - Type variables
  void beginNamedFunctionExpression(Token token) {}

  /// A named function expression which isn't legal syntax in Dart.
  /// Useful for recovering from Javascript code being pasted into a Dart
  /// proram, as it will interpret `function foo() {}` as a named function
  /// expression with return type `function` and name `foo`.
  ///
  /// Substructures:
  /// - Type variables
  /// - Modifiers
  /// - Return type
  /// - Name
  /// - Formals
  /// - Initializers
  /// - Async modifier
  /// - Function body (block or arrow expression).
  void endNamedFunctionExpression(Token endToken) {
    logEvent("NamedFunctionExpression");
  }

  /// Handle the beginning of a local function declaration.  Substructures:
  /// - Metadata
  /// - Type variables
  void beginLocalFunctionDeclaration(Token token) {}

  /// A function declaration.
  ///
  /// Substructures:
  /// - Metadata
  /// - Type variables
  /// - Return type
  /// - Name
  /// - Type variables
  /// - Formals
  /// - Initializers
  /// - Async modifier
  /// - Function body (block or arrow expression).
  void endLocalFunctionDeclaration(Token endToken) {
    logEvent("FunctionDeclaration");
  }

  /// This method is invoked when the parser sees that a function has a
  /// block function body.  This method is not invoked for empty or expression
  /// function bodies, see the corresponding methods [handleEmptyFunctionBody]
  /// and [handleExpressionFunctionBody].
  void beginBlockFunctionBody(Token token) {}

  /// This method is invoked by the parser after it finished parsing a block
  /// function body.  This method is not invoked for empty or expression
  /// function bodies, see the corresponding methods [handleEmptyFunctionBody]
  /// and [handleExpressionFunctionBody].  The [beginToken] is the '{' token,
  /// and the [endToken] is the '}' token of the block.  The number of
  /// statements is given as the [count] parameter.
  void endBlockFunctionBody(int count, Token beginToken, Token endToken) {
    logEvent("BlockFunctionBody");
  }

  void handleNoFunctionBody(Token token) {
    logEvent("NoFunctionBody");
  }

  /// Handle the end of a function body that was skipped by the parser.
  ///
  /// The boolean [isExpressionBody] indicates whether the function body that
  /// was skipped used "=>" syntax.
  void handleFunctionBodySkipped(Token token, bool isExpressionBody) {}

  void beginFunctionName(Token token) {}

  void endFunctionName(Token beginToken, Token token) {
    logEvent("FunctionName");
  }

  void beginFunctionTypeAlias(Token token) {}

  /// Handle the end of a typedef declaration.
  ///
  /// If [equals] is null, then we have the following substructures:
  /// - Metadata
  /// - Return type
  /// - Name (identifier)
  /// - Alias type variables
  /// - Formal parameters
  ///
  /// If [equals] is not null, then the have the following substructures:
  /// - Metadata
  /// - Name (identifier)
  /// - Alias type variables
  /// - Type (FunctionTypeAnnotation)
  void endFunctionTypeAlias(
      Token typedefKeyword, Token equals, Token endToken) {
    logEvent("FunctionTypeAlias");
  }

  void beginMixinApplication(Token token) {}

  /// Handle the end of a mixin application construct (e.g. "A with B, C").
  /// Substructures:
  /// - supertype
  /// - mixin types (TypeList)
  void endMixinApplication(Token withKeyword) {
    logEvent("MixinApplication");
  }

  /// Handle the beginning of a named mixin application.
  /// [beginToken] may be the same as [name], or may point to modifiers
  /// (or extraneous modifiers in the case of recovery) preceding [name].
  void beginNamedMixinApplication(
      Token begin, Token abstractToken, Token name) {}

  /// Handle the end of a named mixin declaration.  Substructures:
  /// - metadata
  /// - modifiers
  /// - class name
  /// - type variables
  /// - mixin application
  /// - implemented types (TypeList)
  ///
  /// TODO(paulberry,ahe): it seems inconsistent that for a named mixin
  /// application, the implemented types are a TypeList, whereas for a class
  /// declaration, each implemented type is listed separately on the stack, and
  /// the number of implemented types is passed as a parameter.
  void endNamedMixinApplication(Token begin, Token classKeyword, Token equals,
      Token implementsKeyword, Token endToken) {
    logEvent("NamedMixinApplication");
  }

  void beginHide(Token hideKeyword) {}

  /// Handle the end of a "hide" combinator.  Substructures:
  /// - hidden names (IdentifierList)
  void endHide(Token hideKeyword) {
    logEvent("Hide");
  }

  void handleIdentifierList(int count) {
    logEvent("IdentifierList");
  }

  void beginTypeList(Token token) {}

  void endTypeList(int count) {
    logEvent("TypeList");
  }

  void beginIfStatement(Token token) {}

  void endIfStatement(Token ifToken, Token elseToken) {
    logEvent("IfStatement");
  }

  void beginThenStatement(Token token) {}

  void endThenStatement(Token token) {
    logEvent("ThenStatement");
  }

  void beginElseStatement(Token token) {}

  void endElseStatement(Token token) {
    logEvent("ElseStatement");
  }

  void beginImport(Token importKeyword) {}

  /// Signals that the current import is deferred and/or has a prefix
  /// depending upon whether [deferredKeyword] and [asKeyword]
  /// are not `null` respectively. Substructures:
  /// - prefix identifier (only if asKeyword != null)
  void handleImportPrefix(Token deferredKeyword, Token asKeyword) {
    logEvent("ImportPrefix");
  }

  /// Handle the end of an import directive.  Substructures:
  /// - metadata
  /// - uri
  /// - conditional uris
  /// - prefix identifier
  /// - combinators
  void endImport(Token importKeyword, Token semicolon) {
    logEvent("Import");
  }

  /// Handle recovery associated with an import directive.
  /// This may be called multiple times after [endImport]
  /// to recover information about the previous import directive.
  /// The substructures are a subset of and in the same order as [endImport]:
  /// - conditional uris
  /// - prefix identifier
  /// - combinators
  void handleRecoverImport(Token semicolon) {
    logEvent("ImportRecovery");
  }

  void beginConditionalUris(Token token) {}

  void endConditionalUris(int count) {
    logEvent("ConditionalUris");
  }

  void beginConditionalUri(Token ifKeyword) {}

  /// Handle the end of a conditional URI construct.  Substructures:
  /// - Dotted name
  /// - Condition (literal string; only if [equalSign] != null)
  /// - URI (literal string)
  void endConditionalUri(Token ifKeyword, Token leftParen, Token equalSign) {
    logEvent("ConditionalUri");
  }

  void handleDottedName(int count, Token firstIdentifier) {
    logEvent("DottedName");
  }

  void beginImplicitCreationExpression(Token token) {}

  void endImplicitCreationExpression(Token token) {
    logEvent("ImplicitCreationExpression");
  }

  void beginInitializedIdentifier(Token token) {}

  void endInitializedIdentifier(Token nameToken) {
    logEvent("InitializedIdentifier");
  }

  void beginFieldInitializer(Token token) {}

  /// Handle the end of a field initializer.  Substructures:
  /// - Initializer expression
  void endFieldInitializer(Token assignment, Token token) {
    logEvent("FieldInitializer");
  }

  /// Handle the lack of a field initializer.
  void handleNoFieldInitializer(Token token) {
    logEvent("NoFieldInitializer");
  }

  void beginVariableInitializer(Token token) {}

  /// Handle the end of a variable initializer. Substructures:
  /// - Initializer expression.
  void endVariableInitializer(Token assignmentOperator) {
    logEvent("VariableInitializer");
  }

  /// Used when a variable has no initializer.
  void handleNoVariableInitializer(Token token) {
    logEvent("NoVariableInitializer");
  }

  void beginInitializer(Token token) {}

  void endInitializer(Token token) {
    logEvent("ConstructorInitializer");
  }

  void beginInitializers(Token token) {}

  void endInitializers(int count, Token beginToken, Token endToken) {
    logEvent("Initializers");
  }

  void handleNoInitializers() {
    logEvent("NoInitializers");
  }

  /// Called after the listener has recovered from an invalid expression. The
  /// parser will resume parsing from [token]. Exactly where the parser will
  /// resume parsing is unspecified.
  void handleInvalidExpression(Token token) {
    logEvent("InvalidExpression");
  }

  /// Called after the listener has recovered from an invalid function
  /// body. The parser expected an open curly brace `{` and will resume parsing
  /// from [token] as if a function body had preceeded it.
  void handleInvalidFunctionBody(Token token) {
    logEvent("InvalidFunctionBody");
  }

  /// Called after the listener has recovered from an invalid type. The parser
  /// expected an identifier, and will resume parsing type arguments from
  /// [token].
  void handleInvalidTypeReference(Token token) {
    logEvent("InvalidTypeReference");
  }

  void handleLabel(Token token) {
    logEvent("Label");
  }

  void beginLabeledStatement(Token token, int labelCount) {}

  void endLabeledStatement(int labelCount) {
    logEvent("LabeledStatement");
  }

  void beginLibraryName(Token token) {}

  /// Handle the end of a library directive.  Substructures:
  /// - Metadata
  /// - Library name (a qualified identifier)
  void endLibraryName(Token libraryKeyword, Token semicolon) {
    logEvent("LibraryName");
  }

  void beginLiteralMapEntry(Token token) {}

  void endLiteralMapEntry(Token colon, Token endToken) {
    logEvent("LiteralMapEntry");
  }

  void beginLiteralString(Token token) {}

  void handleInterpolationExpression(Token leftBracket, Token rightBracket) {}

  void endLiteralString(int interpolationCount, Token endToken) {
    logEvent("LiteralString");
  }

  void handleStringJuxtaposition(int literalCount) {
    logEvent("StringJuxtaposition");
  }

  void beginMember() {}

  /// Handle an invalid member declaration. Substructures:
  /// - metadata
  void handleInvalidMember(Token endToken) {
    logEvent("InvalidMember");
  }

  /// This event is added for convenience. Normally, one should override
  /// [endMethod] or [endFields] instead.
  void endMember() {
    logEvent("Member");
  }

  /// Handle the beginning of a method declaration.  Substructures:
  /// - metadata
  void beginMethod(Token externalToken, Token staticToken, Token covariantToken,
      Token varFinalOrConst, Token name) {}

  /// Handle the end of a method declaration.  Substructures:
  /// - metadata
  /// - return type
  /// - method name (identifier, possibly qualified)
  /// - type variables
  /// - formal parameters
  /// - initializers
  /// - async marker
  /// - body
  void endMethod(
      Token getOrSet, Token beginToken, Token beginParam, Token endToken) {
    logEvent("Method");
  }

  void beginMetadataStar(Token token) {}

  void endMetadataStar(int count) {
    logEvent("MetadataStar");
  }

  void beginMetadata(Token token) {}

  /// Handle the end of a metadata annotation.  Substructures:
  /// - Identifier
  /// - Type arguments
  /// - Constructor name (only if [periodBeforeName] is not `null`)
  /// - Arguments
  void endMetadata(Token beginToken, Token periodBeforeName, Token endToken) {
    logEvent("Metadata");
  }

  void beginOptionalFormalParameters(Token token) {}

  void endOptionalFormalParameters(
      int count, Token beginToken, Token endToken) {
    logEvent("OptionalFormalParameters");
  }

  void beginPart(Token token) {}

  /// Handle the end of a part directive.  Substructures:
  /// - metadata
  /// - uri
  void endPart(Token partKeyword, Token semicolon) {
    logEvent("Part");
  }

  void beginPartOf(Token token) {}

  /// Handle the end of a "part of" directive.  Substructures:
  /// - Metadata
  /// - Library name (a qualified identifier)
  ///
  /// If [hasName] is true, this part refers to its library by name, otherwise,
  /// by URI.
  void endPartOf(
      Token partKeyword, Token ofKeyword, Token semicolon, bool hasName) {
    logEvent("PartOf");
  }

  void beginRedirectingFactoryBody(Token token) {}

  void endRedirectingFactoryBody(Token beginToken, Token endToken) {
    logEvent("RedirectingFactoryBody");
  }

  void beginReturnStatement(Token token) {}

  /// Handle the end of a `native` function.
  /// The [handleNativeClause] event is sent prior to this event.
  void handleNativeFunctionBody(Token nativeToken, Token semicolon) {
    logEvent("NativeFunctionBody");
  }

  /// Called after the [handleNativeClause] event when the parser determines
  /// that the native clause should be discarded / ignored.
  /// For example, this method is called a native clause is followed by
  /// a function body.
  void handleNativeFunctionBodyIgnored(Token nativeToken, Token semicolon) {
    logEvent("NativeFunctionBodyIgnored");
  }

  /// Handle the end of a `native` function that was skipped by the parser.
  /// The [handleNativeClause] event is sent prior to this event.
  void handleNativeFunctionBodySkipped(Token nativeToken, Token semicolon) {
    logEvent("NativeFunctionBodySkipped");
  }

  /// This method is invoked when a function has the empty body.
  void handleEmptyFunctionBody(Token semicolon) {
    logEvent("EmptyFunctionBody");
  }

  /// This method is invoked when parser finishes parsing the corresponding
  /// expression of the expression function body.
  void handleExpressionFunctionBody(Token arrowToken, Token endToken) {
    logEvent("ExpressionFunctionBody");
  }

  void endReturnStatement(
      bool hasExpression, Token beginToken, Token endToken) {
    logEvent("ReturnStatement");
  }

  void handleSend(Token beginToken, Token endToken) {
    logEvent("Send");
  }

  void beginShow(Token showKeyword) {}

  /// Handle the end of a "show" combinator.  Substructures:
  /// - shown names (IdentifierList)
  void endShow(Token showKeyword) {
    logEvent("Show");
  }

  void beginSwitchStatement(Token token) {}

  void endSwitchStatement(Token switchKeyword, Token endToken) {
    logEvent("SwitchStatement");
  }

  void beginSwitchBlock(Token token) {}

  void endSwitchBlock(int caseCount, Token beginToken, Token endToken) {
    logEvent("SwitchBlock");
  }

  void beginLiteralSymbol(Token token) {}

  void endLiteralSymbol(Token hashToken, int identifierCount) {
    logEvent("LiteralSymbol");
  }

  void handleThrowExpression(Token throwToken, Token endToken) {
    logEvent("ThrowExpression");
  }

  void beginRethrowStatement(Token token) {}

  void endRethrowStatement(Token rethrowToken, Token endToken) {
    logEvent("RethrowStatement");
  }

  /// This event is added for convenience. Normally, one should use
  /// [endClassDeclaration], [endNamedMixinApplication], [endEnum],
  /// [endFunctionTypeAlias], [endLibraryName], [endImport], [endExport],
  /// [endPart], [endPartOf], [endTopLevelFields], or [endTopLevelMethod].
  void endTopLevelDeclaration(Token token) {
    logEvent("TopLevelDeclaration");
  }

  /// Called by the [Parser] when it recovers from an invalid top level
  /// declaration, where [endToken] is the last token in the declaration
  /// This is called after the begin/end metadata star events,
  /// and is followed by [endTopLevelDeclaration].
  ///
  /// Substructures:
  /// - metadata
  void handleInvalidTopLevelDeclaration(Token endToken) {
    logEvent("InvalidTopLevelDeclaration");
  }

  /// Marks the beginning of a top level field or method declaration.
  /// Doesn't have a corresponding end event.
  /// See [endTopLevelFields] and [endTopLevelMethod].
  void beginTopLevelMember(Token token) {}

  /// Handle the end of a top level variable declaration.  Substructures:
  /// - Metadata
  /// - Type
  /// - Repeated [count] times:
  ///   - Variable name (identifier)
  ///   - Field initializer
  /// Doesn't have a corresponding begin event.
  /// Use [beginTopLevelMember] instead.
  void endTopLevelFields(Token staticToken, Token covariantToken,
      Token varFinalOrConst, int count, Token beginToken, Token endToken) {
    logEvent("TopLevelFields");
  }

  void beginTopLevelMethod(Token lastConsumed, Token externalToken) {}

  /// Handle the end of a top level method.  Substructures:
  /// - metadata
  /// - modifiers
  /// - return type
  /// - identifier
  /// - type variables
  /// - formal parameters
  /// - async marker
  /// - body
  void endTopLevelMethod(Token beginToken, Token getOrSet, Token endToken) {
    logEvent("TopLevelMethod");
  }

  void beginTryStatement(Token token) {}

  void handleCaseMatch(Token caseKeyword, Token colon) {
    logEvent("CaseMatch");
  }

  void beginCatchClause(Token token) {}

  void endCatchClause(Token token) {
    logEvent("CatchClause");
  }

  void handleCatchBlock(Token onKeyword, Token catchKeyword, Token comma) {
    logEvent("CatchBlock");
  }

  void handleFinallyBlock(Token finallyKeyword) {
    logEvent("FinallyBlock");
  }

  void endTryStatement(int catchCount, Token tryKeyword, Token finallyKeyword) {
    logEvent("TryStatement");
  }

  void handleType(Token beginToken) {
    logEvent("Type");
  }

  void handleNoName(Token token) {
    logEvent("NoName");
  }

  void beginFunctionType(Token beginToken) {}

  /// Handle the end of a generic function type declaration.
  ///
  /// Substructures:
  /// - Type variables
  /// - Return type
  /// - Formal parameters
  void endFunctionType(Token functionToken) {
    logEvent("FunctionType");
  }

  void beginTypeArguments(Token token) {}

  void endTypeArguments(int count, Token beginToken, Token endToken) {
    logEvent("TypeArguments");
  }

  void handleNoTypeArguments(Token token) {
    logEvent("NoTypeArguments");
  }

  /// Handle the begin of a type formal parameter (e.g. "X extends Y").
  /// Substructures:
  /// - Metadata
  /// - Name (identifier)
  void beginTypeVariable(Token token) {}

  /// Called when [beginTypeVariable] has been called for all of the variables
  /// in a group, and before [endTypeVariable] has been called for any of the
  /// variables in that same group.
  void handleTypeVariablesDefined(Token token, int count) {}

  /// Handle the end of a type formal parameter (e.g. "X extends Y")
  /// where [index] is the index of the type variable in the list of
  /// type variables being declared.
  ///
  /// Substructures:
  /// - Type bound
  ///
  /// See [beginTypeVariable] for additional substructures.
  void endTypeVariable(Token token, int index, Token extendsOrSuper) {
    logEvent("TypeVariable");
  }

  void beginTypeVariables(Token token) {}

  void endTypeVariables(Token beginToken, Token endToken) {
    logEvent("TypeVariables");
  }

  void beginFunctionExpression(Token token) {}

  /// Handle the end of a function expression (e.g. "() { ... }").
  /// Substructures:
  /// - Type variables
  /// - Formal parameters
  /// - Async marker
  /// - Body
  void endFunctionExpression(Token beginToken, Token token) {
    logEvent("FunctionExpression");
  }

  /// Handle the start of a variables declaration.  Substructures:
  /// - Metadata
  /// - Type
  void beginVariablesDeclaration(Token token, Token varFinalOrConst) {}

  void endVariablesDeclaration(int count, Token endToken) {
    logEvent("VariablesDeclaration");
  }

  void beginWhileStatement(Token token) {}

  void endWhileStatement(Token whileKeyword, Token endToken) {
    logEvent("WhileStatement");
  }

  void handleAsOperator(Token operator) {
    logEvent("AsOperator");
  }

  void handleAssignmentExpression(Token token) {
    logEvent("AssignmentExpression");
  }

  /// Called when the parser encounters a binary operator, in between the LHS
  /// and RHS subexpressions.
  ///
  /// Not called when the binary operator is `.`, `?.`, or `..`.
  void beginBinaryExpression(Token token) {}

  void endBinaryExpression(Token token) {
    logEvent("BinaryExpression");
  }

  /// Called when the parser encounters a `?` operator and begins parsing a
  /// conditional expression.
  void beginConditionalExpression(Token question) {}

  /// Called when the parser encounters a `:` operator in a conditional
  /// expression.
  void handleConditionalExpressionColon() {}

  /// Called when the parser finishes processing a conditional expression.
  void endConditionalExpression(Token question, Token colon) {
    logEvent("ConditionalExpression");
  }

  void beginConstExpression(Token constKeyword) {}

  void endConstExpression(Token token) {
    logEvent("ConstExpression");
  }

  /// Handle the start of a function typed formal parameter.  Substructures:
  /// - type variables
  void beginFunctionTypedFormalParameter(Token token) {}

  /// Handle the end of a function typed formal parameter.  Substructures:
  /// - type variables
  /// - return type
  /// - formal parameters
  void endFunctionTypedFormalParameter(Token nameToken) {
    logEvent("FunctionTypedFormalParameter");
  }

  /// Handle an identifier token.
  ///
  /// [context] indicates what kind of construct the identifier appears in.
  void handleIdentifier(Token token, IdentifierContext context) {
    logEvent("Identifier");
  }

  void handleIndexedExpression(
      Token openSquareBracket, Token closeSquareBracket) {
    logEvent("IndexedExpression");
  }

  void handleIsOperator(Token isOperator, Token not) {
    logEvent("IsOperator");
  }

  void handleLiteralBool(Token token) {
    logEvent("LiteralBool");
  }

  void handleBreakStatement(
      bool hasTarget, Token breakKeyword, Token endToken) {
    logEvent("BreakStatement");
  }

  void handleContinueStatement(
      bool hasTarget, Token continueKeyword, Token endToken) {
    logEvent("ContinueStatement");
  }

  void handleEmptyStatement(Token token) {
    logEvent("EmptyStatement");
  }

  void beginAssert(Token assertKeyword, Assert kind) {}

  void endAssert(Token assertKeyword, Assert kind, Token leftParenthesis,
      Token commaToken, Token semicolonToken) {
    logEvent("Assert");
  }

  /** Called with either the token containing a double literal, or
    * an immediately preceding "unary plus" token.
    */
  void handleLiteralDouble(Token token) {
    logEvent("LiteralDouble");
  }

  /** Called with either the token containing an integer literal,
    * or an immediately preceding "unary plus" token.
    */
  void handleLiteralInt(Token token) {
    logEvent("LiteralInt");
  }

  void handleLiteralList(
      int count, Token leftBracket, Token constKeyword, Token rightBracket) {
    logEvent("LiteralList");
  }

  void handleLiteralMap(
      int count, Token leftBrace, Token constKeyword, Token rightBrace) {
    logEvent("LiteralMap");
  }

  void handleLiteralNull(Token token) {
    logEvent("LiteralNull");
  }

  void handleNativeClause(Token nativeToken, bool hasName) {
    logEvent("NativeClause");
  }

  void handleNamedArgument(Token colon) {
    logEvent("NamedArgument");
  }

  void beginNewExpression(Token token) {}

  void endNewExpression(Token token) {
    logEvent("NewExpression");
  }

  void handleNoArguments(Token token) {
    logEvent("NoArguments");
  }

  void handleNoExpression(Token token) {
    logEvent("NoExpression");
  }

  void handleNoConstructorReferenceContinuationAfterTypeArguments(Token token) {
    logEvent("NoConstructorReferenceContinuationAfterTypeArguments");
  }

  void handleNoType(Token lastConsumed) {
    logEvent("NoType");
  }

  void handleNoTypeVariables(Token token) {
    logEvent("NoTypeVariables");
  }

  void handleOperator(Token token) {
    logEvent("Operator");
  }

  void handleSymbolVoid(Token token) {
    logEvent("SymbolVoid");
  }

  /// Handle the end of a construct of the form "operator <token>".
  void handleOperatorName(Token operatorKeyword, Token token) {
    logEvent("OperatorName");
  }

  /// Handle the end of a construct of the form "operator <token>"
  /// where <token> is not a valid operator token.
  void handleInvalidOperatorName(Token operatorKeyword, Token token) {
    logEvent("InvalidOperatorName");
  }

  /// Handle the condition in a control structure:
  /// - if statement
  /// - do while loop
  /// - switch statement
  /// - while loop
  void handleParenthesizedCondition(Token token) {
    logEvent("ParenthesizedCondition");
  }

  /// Handle a parenthesized expression.
  /// These may be within the condition expression of a control structure
  /// but will not be the condition of a control structure.
  void handleParenthesizedExpression(Token token) {
    logEvent("ParenthesizedExpression");
  }

  /// Handle a construct of the form "identifier.identifier" occurring in a part
  /// of the grammar where expressions in general are not allowed.
  /// Substructures:
  /// - Qualified identifier (before the period)
  /// - Identifier (after the period)
  void handleQualified(Token period) {
    logEvent("Qualified");
  }

  void handleStringPart(Token token) {
    logEvent("StringPart");
  }

  void handleSuperExpression(Token token, IdentifierContext context) {
    logEvent("SuperExpression");
  }

  void beginSwitchCase(int labelCount, int expressionCount, Token firstToken) {}

  void endSwitchCase(
      int labelCount,
      int expressionCount,
      Token defaultKeyword,
      Token colonAfterDefault,
      int statementCount,
      Token firstToken,
      Token endToken) {
    logEvent("SwitchCase");
  }

  void handleThisExpression(Token token, IdentifierContext context) {
    logEvent("ThisExpression");
  }

  void handleUnaryPostfixAssignmentExpression(Token token) {
    logEvent("UnaryPostfixAssignmentExpression");
  }

  void handleUnaryPrefixExpression(Token token) {
    logEvent("UnaryPrefixExpression");
  }

  void handleUnaryPrefixAssignmentExpression(Token token) {
    logEvent("UnaryPrefixAssignmentExpression");
  }

  void beginFormalParameterDefaultValueExpression() {}

  void endFormalParameterDefaultValueExpression() {
    logEvent("FormalParameterDefaultValueExpression");
  }

  void handleValuedFormalParameter(Token equals, Token token) {
    logEvent("ValuedFormalParameter");
  }

  void handleFormalParameterWithoutValue(Token token) {
    logEvent("FormalParameterWithoutValue");
  }

  void handleVoidKeyword(Token token) {
    logEvent("VoidKeyword");
  }

  void beginYieldStatement(Token token) {}

  void endYieldStatement(Token yieldToken, Token starToken, Token endToken) {
    logEvent("YieldStatement");
  }

  /// The parser noticed a syntax error, but was able to recover from it. The
  /// error should be reported using the [message], and the code between the
  /// beginning of the [startToken] and the end of the [endToken] should be
  /// highlighted. The [startToken] and [endToken] can be the same token.
  void handleRecoverableError(
      Message message, Token startToken, Token endToken) {}

  @override
  void handleUnescapeError(
      Message message, Token location, int stringOffset, int length) {
    handleRecoverableError(message, location, location);
  }

  /// Signals to the listener that the previous statement contained a semantic
  /// error (described by the given [message]). This method can also be called
  /// after [handleExpressionFunctionBody], in which case it signals that the
  /// implicit return statement of the function contained a semantic error.
  void handleInvalidStatement(Token token, Message message) {
    handleRecoverableError(message, token, token);
  }

  void handleScript(Token token) {
    logEvent("Script");
  }

  /// A type has been just parsed, and the parser noticed that the next token
  /// has a type substitution comment /*=T*. So, the type that has been just
  /// parsed should be discarded, and a new type should be parsed instead.
  void discardTypeReplacedWithCommentTypeAssign() {}

  /// A single comment reference has been found
  /// where [referenceSource] is the text between the `[` and `]`
  /// and [referenceOffset] is the character offset in the token stream.
  ///
  /// This event is generated by the parser when the parser's
  /// `parseCommentReferences` method is called. For further processing,
  /// a listener may scan the [referenceSource] and then pass the resulting
  /// token stream to the parser's `parseOneCommentReference` method.
  void handleCommentReferenceText(String referenceSource, int referenceOffset) {
    logEvent("CommentReferenceText");
  }

  /// A single comment reference has been parsed.
  /// * [newKeyword] may be null.
  /// * [prefix] and [period] are either both tokens or both `null`.
  /// * [token] can be an identifier or an operator.
  ///
  /// This event is generated by the parser when the parser's
  /// `parseOneCommentReference` method is called.
  void handleCommentReference(
      Token newKeyword, Token prefix, Token period, Token token) {}

  /// This event is generated by the parser when the parser's
  /// `parseOneCommentReference` method is called.
  void handleNoCommentReference() {}
}