// Copyright (c) 2018, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'package:kernel/ast.dart'
    show Arguments, Expression, InvalidExpression, Node, Statement;

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

import '../constant_context.dart' show ConstantContext;

import '../fasta_codes.dart'
    show
        LocatedMessage,
        messageLoadLibraryTakesNoArguments,
        messageSuperAsExpression,
        templateNotAPrefixInTypeAnnotation;

import '../messages.dart' show Message, noLength;

import '../names.dart' show callName, equalsName, indexGetName, indexSetName;

import '../parser.dart' show lengthForToken, lengthOfSpan, offsetForToken;

import '../problems.dart' show unhandled, unsupported;

import 'body_builder.dart' show Identifier, noLocation;

import 'constness.dart' show Constness;

import 'expression_generator.dart'
    show
        ContextAwareGenerator,
        DeferredAccessGenerator,
        DelayedAssignment,
        DelayedPostfixIncrement,
        ErroneousExpressionGenerator,
        ExpressionGenerator,
        Generator,
        IndexedAccessGenerator,
        LargeIntAccessGenerator,
        LoadLibraryGenerator,
        NullAwarePropertyAccessGenerator,
        PropertyAccessGenerator,
        ReadOnlyAccessGenerator,
        StaticAccessGenerator,
        SuperIndexedAccessGenerator,
        SuperPropertyAccessGenerator,
        ThisIndexedAccessGenerator,
        ThisPropertyAccessGenerator,
        TypeUseGenerator,
        UnlinkedGenerator,
        UnresolvedNameGenerator,
        VariableUseGenerator;

import 'expression_generator_helper.dart' show ExpressionGeneratorHelper;

import 'forest.dart' show Forest;

import 'kernel_builder.dart'
    show LoadLibraryBuilder, PrefixBuilder, UnlinkedDeclaration;

import 'kernel_api.dart' show NameSystem, printNodeOn, printQualifiedNameOn;

import 'kernel_ast_api.dart'
    show
        Constructor,
        DartType,
        Field,
        Initializer,
        InvalidType,
        Let,
        Member,
        Name,
        Procedure,
        PropertySet,
        ShadowComplexAssignment,
        ShadowIllegalAssignment,
        ShadowIndexAssign,
        ShadowMethodInvocation,
        NullAwarePropertyGetJudgment,
        ShadowPropertyAssign,
        PropertyGetJudgment,
        ShadowStaticAssignment,
        ShadowSuperMethodInvocation,
        SuperPropertyGetJudgment,
        VariableAssignmentJudgment,
        ShadowSyntheticExpression,
        VariableDeclarationJudgment,
        VariableGetJudgment,
        StaticSet,
        SuperMethodInvocation,
        SuperPropertySet,
        Throw,
        TreeNode,
        TypeParameter,
        VariableDeclaration,
        VariableGet,
        VariableSet;

import 'kernel_builder.dart'
    show
        Declaration,
        KernelClassBuilder,
        KernelInvalidTypeBuilder,
        LoadLibraryBuilder,
        PrefixBuilder,
        TypeDeclarationBuilder;

part 'kernel_expression_generator_impl.dart';

abstract class KernelExpressionGenerator
    implements ExpressionGenerator<Expression, Statement, Arguments> {
  ExpressionGeneratorHelper<Expression, Statement, Arguments> get helper;

  Token get token;

  Forest<Expression, Statement, Token, Arguments> get forest;

  @override
  Expression buildSimpleRead() {
    return _finish(_makeSimpleRead(), null);
  }

  @override
  Expression buildAssignment(Expression value, {bool voidContext: false}) {
    var complexAssignment = startComplexAssignment(value);
    return _finish(_makeSimpleWrite(value, voidContext, complexAssignment),
        complexAssignment);
  }

  @override
  Expression buildNullAwareAssignment(
      Expression value, DartType type, int offset,
      {bool voidContext: false}) {
    var complexAssignment = startComplexAssignment(value);
    if (voidContext) {
      var nullAwareCombiner = helper.storeOffset(
          forest.conditionalExpression(
              buildIsNull(_makeRead(complexAssignment), offset, helper),
              null,
              _makeWrite(value, false, complexAssignment),
              null,
              helper.storeOffset(forest.literalNull(null), offset)),
          offset);
      complexAssignment?.nullAwareCombiner = nullAwareCombiner;
      return _finish(nullAwareCombiner, complexAssignment);
    }
    var tmp = new VariableDeclaration.forValue(_makeRead(complexAssignment));
    var nullAwareCombiner = helper.storeOffset(
        forest.conditionalExpression(
            buildIsNull(new VariableGet(tmp), offset, helper),
            null,
            _makeWrite(value, false, complexAssignment),
            null,
            new VariableGet(tmp)),
        offset);
    complexAssignment?.nullAwareCombiner = nullAwareCombiner;
    return _finish(makeLet(tmp, nullAwareCombiner), complexAssignment);
  }

  @override
  Expression buildCompoundAssignment(Name binaryOperator, Expression value,
      {int offset: TreeNode.noOffset,
      bool voidContext: false,
      Procedure interfaceTarget,
      bool isPreIncDec: false}) {
    var complexAssignment = startComplexAssignment(value);
    complexAssignment?.isPreIncDec = isPreIncDec;
    var combiner = makeBinary(_makeRead(complexAssignment), binaryOperator,
        interfaceTarget, value, helper,
        offset: offset);
    complexAssignment?.combiner = combiner;
    return _finish(_makeWrite(combiner, voidContext, complexAssignment),
        complexAssignment);
  }

  @override
  Expression buildPrefixIncrement(Name binaryOperator,
      {int offset: TreeNode.noOffset,
      bool voidContext: false,
      Procedure interfaceTarget}) {
    return buildCompoundAssignment(
        binaryOperator, helper.storeOffset(forest.literalInt(1, null), offset),
        offset: offset,
        voidContext: voidContext,
        interfaceTarget: interfaceTarget,
        isPreIncDec: true);
  }

  @override
  Expression buildPostfixIncrement(Name binaryOperator,
      {int offset: TreeNode.noOffset,
      bool voidContext: false,
      Procedure interfaceTarget}) {
    if (voidContext) {
      return buildPrefixIncrement(binaryOperator,
          offset: offset, voidContext: true, interfaceTarget: interfaceTarget);
    }
    var rhs = helper.storeOffset(forest.literalInt(1, null), offset);
    var complexAssignment = startComplexAssignment(rhs);
    var value = new VariableDeclaration.forValue(_makeRead(complexAssignment));
    valueAccess() => new VariableGet(value);
    var combiner = makeBinary(
        valueAccess(), binaryOperator, interfaceTarget, rhs, helper,
        offset: offset);
    complexAssignment?.combiner = combiner;
    complexAssignment?.isPostIncDec = true;
    var dummy = new VariableDeclarationJudgment.forValue(
        _makeWrite(combiner, true, complexAssignment),
        helper.functionNestingLevel);
    return _finish(
        makeLet(value, makeLet(dummy, valueAccess())), complexAssignment);
  }

  @override
  Expression makeInvalidRead() {
    return buildThrowNoSuchMethodError(
        forest.literalNull(token), forest.argumentsEmpty(noLocation),
        isGetter: true);
  }

  @override
  Expression makeInvalidWrite(Expression value) {
    return buildThrowNoSuchMethodError(forest.literalNull(token),
        forest.arguments(<Expression>[value], noLocation),
        isSetter: true);
  }

  Expression _makeSimpleRead() => _makeRead(null);

  Expression _makeSimpleWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    return _makeWrite(value, voidContext, complexAssignment);
  }

  Expression _makeRead(ShadowComplexAssignment complexAssignment);

  Expression _makeWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment);

  Expression _finish(
      Expression body, ShadowComplexAssignment complexAssignment) {
    if (complexAssignment != null) {
      complexAssignment.desugared = body;
      return complexAssignment;
    } else {
      return body;
    }
  }

  /// Creates a data structure for tracking the desugaring of a complex
  /// assignment expression whose right hand side is [rhs].
  ShadowComplexAssignment startComplexAssignment(Expression rhs) =>
      new ShadowIllegalAssignment(rhs);
}

abstract class KernelGenerator = Generator<Expression, Statement, Arguments>
    with KernelExpressionGenerator;

class KernelVariableUseGenerator extends KernelGenerator
    with VariableUseGenerator<Expression, Statement, Arguments> {
  final VariableDeclaration variable;

  final DartType promotedType;

  KernelVariableUseGenerator(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token,
      this.variable,
      this.promotedType)
      : super(helper, token);

  @override
  String get plainNameForRead => variable.name;

  @override
  Expression _makeRead(ShadowComplexAssignment complexAssignment) {
    var fact = helper.typePromoter
        .getFactForAccess(variable, helper.functionNestingLevel);
    var scope = helper.typePromoter.currentScope;
    var read = new VariableGetJudgment(variable, fact, scope)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.read = read;
    return read;
  }

  @override
  Expression _makeWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    helper.typePromoter.mutateVariable(variable, helper.functionNestingLevel);
    var write = variable.isFinal || variable.isConst
        ? makeInvalidWrite(value)
        : new VariableSet(variable, value)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    return write;
  }

  @override
  Expression doInvocation(int offset, Arguments arguments) {
    return helper.buildMethodInvocation(buildSimpleRead(), callName, arguments,
        adjustForImplicitCall(plainNameForRead, offset),
        isImplicitCall: true);
  }

  @override
  ShadowComplexAssignment startComplexAssignment(Expression rhs) =>
      new VariableAssignmentJudgment(rhs);

  @override
  void printOn(StringSink sink) {
    NameSystem syntheticNames = new NameSystem();
    sink.write(", variable: ");
    printNodeOn(variable, sink, syntheticNames: syntheticNames);
    sink.write(", promotedType: ");
    printNodeOn(promotedType, sink, syntheticNames: syntheticNames);
  }
}

class KernelPropertyAccessGenerator extends KernelGenerator
    with PropertyAccessGenerator<Expression, Statement, Arguments> {
  final Expression receiver;

  final Name name;

  final Member getter;

  final Member setter;

  VariableDeclaration _receiverVariable;

  KernelPropertyAccessGenerator.internal(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token,
      this.receiver,
      this.name,
      this.getter,
      this.setter)
      : super(helper, token);

  @override
  String get plainNameForRead => name.name;

  receiverAccess() {
    _receiverVariable ??= new VariableDeclaration.forValue(receiver);
    return new VariableGet(_receiverVariable)
      ..fileOffset = offsetForToken(token);
  }

  @override
  Expression doInvocation(int offset, Arguments arguments) {
    return helper.buildMethodInvocation(receiver, name, arguments, offset);
  }

  @override
  ShadowComplexAssignment startComplexAssignment(Expression rhs) =>
      new ShadowPropertyAssign(receiver, rhs);

  @override
  void printOn(StringSink sink) {
    NameSystem syntheticNames = new NameSystem();
    sink.write(", _receiverVariable: ");
    printNodeOn(_receiverVariable, sink, syntheticNames: syntheticNames);
    sink.write(", receiver: ");
    printNodeOn(receiver, sink, syntheticNames: syntheticNames);
    sink.write(", name: ");
    sink.write(name.name);
    sink.write(", getter: ");
    printQualifiedNameOn(getter, sink, syntheticNames: syntheticNames);
    sink.write(", setter: ");
    printQualifiedNameOn(setter, sink, syntheticNames: syntheticNames);
  }

  @override
  Expression _makeSimpleRead() =>
      new PropertyGetJudgment(receiver, name, getter)
        ..fileOffset = offsetForToken(token);

  @override
  Expression _makeSimpleWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    var write = new PropertySet(receiver, name, value, setter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    return write;
  }

  @override
  Expression _makeRead(ShadowComplexAssignment complexAssignment) {
    var read = new PropertyGetJudgment(receiverAccess(), name, getter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.read = read;
    return read;
  }

  @override
  Expression _makeWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    var write = new PropertySet(receiverAccess(), name, value, setter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    return write;
  }

  @override
  Expression _finish(
      Expression body, ShadowComplexAssignment complexAssignment) {
    return super._finish(makeLet(_receiverVariable, body), complexAssignment);
  }
}

class KernelThisPropertyAccessGenerator extends KernelGenerator
    with ThisPropertyAccessGenerator<Expression, Statement, Arguments> {
  final Name name;

  final Member getter;

  final Member setter;

  KernelThisPropertyAccessGenerator(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token,
      this.name,
      this.getter,
      this.setter)
      : super(helper, token);

  @override
  String get plainNameForRead => name.name;

  @override
  Expression _makeRead(ShadowComplexAssignment complexAssignment) {
    if (getter == null) {
      helper.warnUnresolvedGet(name, offsetForToken(token));
    }
    var read =
        new PropertyGetJudgment(forest.thisExpression(token), name, getter)
          ..fileOffset = offsetForToken(token);
    complexAssignment?.read = read;
    return read;
  }

  @override
  Expression _makeWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    if (setter == null) {
      helper.warnUnresolvedSet(name, offsetForToken(token));
    }
    var write =
        new PropertySet(forest.thisExpression(token), name, value, setter)
          ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    return write;
  }

  @override
  Expression doInvocation(int offset, Arguments arguments) {
    Member interfaceTarget = getter;
    if (interfaceTarget == null) {
      helper.warnUnresolvedMethod(name, offset);
    }
    if (interfaceTarget is Field) {
      // TODO(ahe): In strong mode we should probably rewrite this to
      // `this.name.call(arguments)`.
      interfaceTarget = null;
    }
    return helper.buildMethodInvocation(
        forest.thisExpression(null), name, arguments, offset,
        interfaceTarget: interfaceTarget);
  }

  @override
  ShadowComplexAssignment startComplexAssignment(Expression rhs) =>
      new ShadowPropertyAssign(null, rhs);

  @override
  void printOn(StringSink sink) {
    NameSystem syntheticNames = new NameSystem();
    sink.write(", name: ");
    sink.write(name.name);
    sink.write(", getter: ");
    printQualifiedNameOn(getter, sink, syntheticNames: syntheticNames);
    sink.write(", setter: ");
    printQualifiedNameOn(setter, sink, syntheticNames: syntheticNames);
  }
}

class KernelNullAwarePropertyAccessGenerator extends KernelGenerator
    with NullAwarePropertyAccessGenerator<Expression, Statement, Arguments> {
  final VariableDeclaration receiver;

  final Expression receiverExpression;

  final Name name;

  final Member getter;

  final Member setter;

  final DartType type;

  KernelNullAwarePropertyAccessGenerator(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token,
      this.receiverExpression,
      this.name,
      this.getter,
      this.setter,
      this.type)
      : this.receiver = makeOrReuseVariable(receiverExpression),
        super(helper, token);

  Expression receiverAccess() => new VariableGet(receiver);

  @override
  String get plainNameForRead => name.name;

  @override
  Expression _makeRead(ShadowComplexAssignment complexAssignment) {
    var read = new PropertyGetJudgment(receiverAccess(), name, getter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.read = read;
    return read;
  }

  @override
  Expression _makeWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    var write = new PropertySet(receiverAccess(), name, value, setter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    return write;
  }

  @override
  Expression _finish(
      Expression body, ShadowComplexAssignment complexAssignment) {
    var offset = offsetForToken(token);
    var nullAwareGuard = helper.storeOffset(
        forest.conditionalExpression(
            buildIsNull(receiverAccess(), offset, helper),
            null,
            helper.storeOffset(forest.literalNull(null), offset),
            null,
            body),
        offset);
    if (complexAssignment != null) {
      body = makeLet(receiver, nullAwareGuard);
      ShadowPropertyAssign kernelPropertyAssign = complexAssignment;
      kernelPropertyAssign.nullAwareGuard = nullAwareGuard;
      kernelPropertyAssign.desugared = body;
      return kernelPropertyAssign;
    } else {
      return new NullAwarePropertyGetJudgment(receiver, nullAwareGuard)
        ..fileOffset = offset;
    }
  }

  @override
  Expression doInvocation(int offset, Arguments arguments) {
    return unsupported("doInvocation", offset, uri);
  }

  @override
  ShadowComplexAssignment startComplexAssignment(Expression rhs) =>
      new ShadowPropertyAssign(receiverExpression, rhs);

  @override
  void printOn(StringSink sink) {
    NameSystem syntheticNames = new NameSystem();
    sink.write(", receiver: ");
    printNodeOn(receiver, sink, syntheticNames: syntheticNames);
    sink.write(", receiverExpression: ");
    printNodeOn(receiverExpression, sink, syntheticNames: syntheticNames);
    sink.write(", name: ");
    sink.write(name.name);
    sink.write(", getter: ");
    printQualifiedNameOn(getter, sink, syntheticNames: syntheticNames);
    sink.write(", setter: ");
    printQualifiedNameOn(setter, sink, syntheticNames: syntheticNames);
    sink.write(", type: ");
    printNodeOn(type, sink, syntheticNames: syntheticNames);
  }
}

class KernelSuperPropertyAccessGenerator extends KernelGenerator
    with SuperPropertyAccessGenerator<Expression, Statement, Arguments> {
  final Name name;

  final Member getter;

  final Member setter;

  KernelSuperPropertyAccessGenerator(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token,
      this.name,
      this.getter,
      this.setter)
      : super(helper, token);

  @override
  String get plainNameForRead => name.name;

  @override
  Expression _makeRead(ShadowComplexAssignment complexAssignment) {
    if (getter == null) {
      helper.warnUnresolvedGet(name, offsetForToken(token), isSuper: true);
    }
    // TODO(ahe): Use [DirectPropertyGet] when possible.
    var read = new SuperPropertyGetJudgment(name, getter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.read = read;
    return read;
  }

  @override
  Expression _makeWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    if (setter == null) {
      helper.warnUnresolvedSet(name, offsetForToken(token), isSuper: true);
    }
    // TODO(ahe): Use [DirectPropertySet] when possible.
    var write = new SuperPropertySet(name, value, setter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    return write;
  }

  @override
  Expression doInvocation(int offset, Arguments arguments) {
    if (helper.constantContext != ConstantContext.none) {
      helper.deprecated_addCompileTimeError(
          offset, "Not a constant expression.");
    }
    if (getter == null || isFieldOrGetter(getter)) {
      return helper.buildMethodInvocation(
          buildSimpleRead(), callName, arguments, offset,
          // This isn't a constant expression, but we have checked if a
          // constant expression error should be emitted already.
          isConstantExpression: true,
          isImplicitCall: true);
    } else {
      // TODO(ahe): This could be something like "super.property(...)" where
      // property is a setter.
      return unhandled("${getter.runtimeType}", "doInvocation", offset, uri);
    }
  }

  @override
  ShadowComplexAssignment startComplexAssignment(Expression rhs) =>
      new ShadowPropertyAssign(null, rhs, isSuper: true);

  @override
  void printOn(StringSink sink) {
    NameSystem syntheticNames = new NameSystem();
    sink.write(", name: ");
    sink.write(name.name);
    sink.write(", getter: ");
    printQualifiedNameOn(getter, sink, syntheticNames: syntheticNames);
    sink.write(", setter: ");
    printQualifiedNameOn(setter, sink, syntheticNames: syntheticNames);
  }
}

class KernelIndexedAccessGenerator extends KernelGenerator
    with IndexedAccessGenerator<Expression, Statement, Arguments> {
  final Expression receiver;

  final Expression index;

  final Procedure getter;

  final Procedure setter;

  VariableDeclaration receiverVariable;

  VariableDeclaration indexVariable;

  KernelIndexedAccessGenerator.internal(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token,
      this.receiver,
      this.index,
      this.getter,
      this.setter)
      : super(helper, token);

  Expression indexAccess() {
    indexVariable ??= new VariableDeclaration.forValue(index);
    return new VariableGet(indexVariable)..fileOffset = offsetForToken(token);
  }

  Expression receiverAccess() {
    // We cannot reuse the receiver if it is a variable since it might be
    // reassigned in the index expression.
    receiverVariable ??= new VariableDeclaration.forValue(receiver);
    return new VariableGet(receiverVariable)
      ..fileOffset = offsetForToken(token);
  }

  @override
  Expression _makeSimpleRead() {
    var read = new ShadowMethodInvocation(receiver, indexGetName,
        forest.castArguments(forest.arguments(<Expression>[index], token)),
        interfaceTarget: getter)
      ..fileOffset = offsetForToken(token);
    return read;
  }

  @override
  Expression _makeSimpleWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    if (!voidContext) return _makeWriteAndReturn(value, complexAssignment);
    var write = new ShadowMethodInvocation(
        receiver,
        indexSetName,
        forest
            .castArguments(forest.arguments(<Expression>[index, value], token)),
        interfaceTarget: setter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    return write;
  }

  @override
  Expression _makeRead(ShadowComplexAssignment complexAssignment) {
    var read = new ShadowMethodInvocation(
        receiverAccess(),
        indexGetName,
        forest.castArguments(
            forest.arguments(<Expression>[indexAccess()], token)),
        interfaceTarget: getter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.read = read;
    return read;
  }

  @override
  Expression _makeWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    if (!voidContext) return _makeWriteAndReturn(value, complexAssignment);
    var write = new ShadowMethodInvocation(
        receiverAccess(),
        indexSetName,
        forest.castArguments(
            forest.arguments(<Expression>[indexAccess(), value], token)),
        interfaceTarget: setter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    return write;
  }

  // TODO(dmitryas): remove this method after the "[]=" operator of the Context
  // class is made to return a value.
  Expression _makeWriteAndReturn(
      Expression value, ShadowComplexAssignment complexAssignment) {
    // The call to []= does not return the value like direct-style assignments
    // do.  We need to bind the value in a let.
    var valueVariable = new VariableDeclaration.forValue(value);
    var write = new ShadowMethodInvocation(
        receiverAccess(),
        indexSetName,
        forest.castArguments(forest.arguments(
            <Expression>[indexAccess(), new VariableGet(valueVariable)],
            token)),
        interfaceTarget: setter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    var dummy = new VariableDeclarationJudgment.forValue(
        write, helper.functionNestingLevel);
    return makeLet(
        valueVariable, makeLet(dummy, new VariableGet(valueVariable)));
  }

  @override
  Expression _finish(
      Expression body, ShadowComplexAssignment complexAssignment) {
    return super._finish(
        makeLet(receiverVariable, makeLet(indexVariable, body)),
        complexAssignment);
  }

  @override
  Expression doInvocation(int offset, Arguments arguments) {
    return helper.buildMethodInvocation(
        buildSimpleRead(), callName, arguments, forest.readOffset(arguments),
        isImplicitCall: true);
  }

  @override
  ShadowComplexAssignment startComplexAssignment(Expression rhs) =>
      new ShadowIndexAssign(receiver, index, rhs);

  @override
  void printOn(StringSink sink) {
    NameSystem syntheticNames = new NameSystem();
    sink.write(", receiver: ");
    printNodeOn(receiver, sink, syntheticNames: syntheticNames);
    sink.write(", index: ");
    printNodeOn(index, sink, syntheticNames: syntheticNames);
    sink.write(", getter: ");
    printQualifiedNameOn(getter, sink, syntheticNames: syntheticNames);
    sink.write(", setter: ");
    printQualifiedNameOn(setter, sink, syntheticNames: syntheticNames);
    sink.write(", receiverVariable: ");
    printNodeOn(receiverVariable, sink, syntheticNames: syntheticNames);
    sink.write(", indexVariable: ");
    printNodeOn(indexVariable, sink, syntheticNames: syntheticNames);
  }
}

class KernelThisIndexedAccessGenerator extends KernelGenerator
    with ThisIndexedAccessGenerator<Expression, Statement, Arguments> {
  final Expression index;

  final Procedure getter;

  final Procedure setter;

  VariableDeclaration indexVariable;

  KernelThisIndexedAccessGenerator(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token,
      this.index,
      this.getter,
      this.setter)
      : super(helper, token);

  Expression indexAccess() {
    indexVariable ??= new VariableDeclaration.forValue(index);
    return new VariableGet(indexVariable);
  }

  Expression _makeWriteAndReturn(
      Expression value, ShadowComplexAssignment complexAssignment) {
    var valueVariable = new VariableDeclaration.forValue(value);
    var write = new ShadowMethodInvocation(
        forest.thisExpression(token),
        indexSetName,
        forest.castArguments(forest.arguments(
            <Expression>[indexAccess(), new VariableGet(valueVariable)],
            token)),
        interfaceTarget: setter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    var dummy = new VariableDeclaration.forValue(write);
    return makeLet(
        valueVariable, makeLet(dummy, new VariableGet(valueVariable)));
  }

  @override
  Expression _makeSimpleRead() {
    return new ShadowMethodInvocation(
        forest.thisExpression(token),
        indexGetName,
        forest.castArguments(forest.arguments(<Expression>[index], token)),
        interfaceTarget: getter)
      ..fileOffset = offsetForToken(token);
  }

  @override
  Expression _makeSimpleWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    if (!voidContext) return _makeWriteAndReturn(value, complexAssignment);
    var write = new ShadowMethodInvocation(
        forest.thisExpression(token),
        indexSetName,
        forest
            .castArguments(forest.arguments(<Expression>[index, value], token)),
        interfaceTarget: setter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    return write;
  }

  @override
  Expression _makeRead(ShadowComplexAssignment complexAssignment) {
    var read = new ShadowMethodInvocation(
        forest.thisExpression(token),
        indexGetName,
        forest.castArguments(
            forest.arguments(<Expression>[indexAccess()], token)),
        interfaceTarget: getter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.read = read;
    return read;
  }

  @override
  Expression _makeWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    if (!voidContext) return _makeWriteAndReturn(value, complexAssignment);
    var write = new ShadowMethodInvocation(
        forest.thisExpression(token),
        indexSetName,
        forest.castArguments(
            forest.arguments(<Expression>[indexAccess(), value], token)),
        interfaceTarget: setter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    return write;
  }

  @override
  Expression _finish(
      Expression body, ShadowComplexAssignment complexAssignment) {
    return super._finish(makeLet(indexVariable, body), complexAssignment);
  }

  @override
  Expression doInvocation(int offset, Arguments arguments) {
    return helper.buildMethodInvocation(
        buildSimpleRead(), callName, arguments, offset,
        isImplicitCall: true);
  }

  @override
  ShadowComplexAssignment startComplexAssignment(Expression rhs) =>
      new ShadowIndexAssign(null, index, rhs);

  @override
  void printOn(StringSink sink) {
    NameSystem syntheticNames = new NameSystem();
    sink.write(", index: ");
    printNodeOn(index, sink, syntheticNames: syntheticNames);
    sink.write(", getter: ");
    printQualifiedNameOn(getter, sink, syntheticNames: syntheticNames);
    sink.write(", setter: ");
    printQualifiedNameOn(setter, sink, syntheticNames: syntheticNames);
    sink.write(", indexVariable: ");
    printNodeOn(indexVariable, sink, syntheticNames: syntheticNames);
  }
}

class KernelSuperIndexedAccessGenerator extends KernelGenerator
    with SuperIndexedAccessGenerator<Expression, Statement, Arguments> {
  final Expression index;

  final Member getter;

  final Member setter;

  VariableDeclaration indexVariable;

  KernelSuperIndexedAccessGenerator(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token,
      this.index,
      this.getter,
      this.setter)
      : super(helper, token);

  Expression indexAccess() {
    indexVariable ??= new VariableDeclaration.forValue(index);
    return new VariableGet(indexVariable);
  }

  Expression _makeWriteAndReturn(
      Expression value, ShadowComplexAssignment complexAssignment) {
    var valueVariable = new VariableDeclaration.forValue(value);
    if (setter == null) {
      helper.warnUnresolvedMethod(indexSetName, offsetForToken(token),
          isSuper: true);
    }
    var write = new SuperMethodInvocation(
        indexSetName,
        forest.castArguments(forest.arguments(
            <Expression>[indexAccess(), new VariableGet(valueVariable)],
            token)),
        setter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    var dummy = new VariableDeclaration.forValue(write);
    return makeLet(
        valueVariable, makeLet(dummy, new VariableGet(valueVariable)));
  }

  @override
  Expression _makeSimpleRead() {
    if (getter == null) {
      helper.warnUnresolvedMethod(indexGetName, offsetForToken(token),
          isSuper: true);
    }
    // TODO(ahe): Use [DirectMethodInvocation] when possible.
    return new ShadowSuperMethodInvocation(
        indexGetName,
        forest.castArguments(forest.arguments(<Expression>[index], token)),
        getter)
      ..fileOffset = offsetForToken(token);
  }

  @override
  Expression _makeSimpleWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    if (!voidContext) return _makeWriteAndReturn(value, complexAssignment);
    if (setter == null) {
      helper.warnUnresolvedMethod(indexSetName, offsetForToken(token),
          isSuper: true);
    }
    var write = new SuperMethodInvocation(
        indexSetName,
        forest
            .castArguments(forest.arguments(<Expression>[index, value], token)),
        setter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    return write;
  }

  @override
  Expression _makeRead(ShadowComplexAssignment complexAssignment) {
    if (getter == null) {
      helper.warnUnresolvedMethod(indexGetName, offsetForToken(token),
          isSuper: true);
    }
    var read = new SuperMethodInvocation(
        indexGetName,
        forest.castArguments(
            forest.arguments(<Expression>[indexAccess()], token)),
        getter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.read = read;
    return read;
  }

  @override
  Expression _makeWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    if (!voidContext) return _makeWriteAndReturn(value, complexAssignment);
    if (setter == null) {
      helper.warnUnresolvedMethod(indexSetName, offsetForToken(token),
          isSuper: true);
    }
    var write = new SuperMethodInvocation(
        indexSetName,
        forest.castArguments(
            forest.arguments(<Expression>[indexAccess(), value], token)),
        setter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    return write;
  }

  @override
  Expression _finish(
      Expression body, ShadowComplexAssignment complexAssignment) {
    return super._finish(makeLet(indexVariable, body), complexAssignment);
  }

  @override
  Expression doInvocation(int offset, Arguments arguments) {
    return helper.buildMethodInvocation(
        buildSimpleRead(), callName, arguments, offset,
        isImplicitCall: true);
  }

  @override
  ShadowComplexAssignment startComplexAssignment(Expression rhs) =>
      new ShadowIndexAssign(null, index, rhs, isSuper: true);

  @override
  void printOn(StringSink sink) {
    NameSystem syntheticNames = new NameSystem();
    sink.write(", index: ");
    printNodeOn(index, sink, syntheticNames: syntheticNames);
    sink.write(", getter: ");
    printQualifiedNameOn(getter, sink, syntheticNames: syntheticNames);
    sink.write(", setter: ");
    printQualifiedNameOn(setter, sink, syntheticNames: syntheticNames);
    sink.write(", indexVariable: ");
    printNodeOn(indexVariable, sink, syntheticNames: syntheticNames);
  }
}

class KernelStaticAccessGenerator extends KernelGenerator
    with StaticAccessGenerator<Expression, Statement, Arguments> {
  @override
  final Member readTarget;

  final Member writeTarget;

  KernelStaticAccessGenerator(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token,
      this.readTarget,
      this.writeTarget)
      : assert(readTarget != null || writeTarget != null),
        super(helper, token);

  @override
  String get plainNameForRead => (readTarget ?? writeTarget).name.name;

  @override
  Expression _makeRead(ShadowComplexAssignment complexAssignment) {
    if (readTarget == null) {
      return makeInvalidRead();
    } else {
      var read = helper.makeStaticGet(readTarget, token);
      complexAssignment?.read = read;
      return read;
    }
  }

  @override
  Expression _makeWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    Expression write;
    if (writeTarget == null) {
      write = makeInvalidWrite(value);
    } else {
      write = new StaticSet(writeTarget, value);
      complexAssignment?.write = write;
    }
    write.fileOffset = offsetForToken(token);
    return write;
  }

  @override
  Expression doInvocation(int offset, Arguments arguments) {
    if (helper.constantContext != ConstantContext.none &&
        !helper.isIdentical(readTarget)) {
      helper.deprecated_addCompileTimeError(
          offset, "Not a constant expression.");
    }
    if (readTarget == null || isFieldOrGetter(readTarget)) {
      return helper.buildMethodInvocation(buildSimpleRead(), callName,
          arguments, offset + (readTarget?.name?.name?.length ?? 0),
          // This isn't a constant expression, but we have checked if a
          // constant expression error should be emitted already.
          isConstantExpression: true,
          isImplicitCall: true);
    } else {
      return helper.buildStaticInvocation(readTarget, arguments,
          charOffset: offset);
    }
  }

  @override
  ShadowComplexAssignment startComplexAssignment(Expression rhs) =>
      new ShadowStaticAssignment(rhs);

  @override
  void printOn(StringSink sink) {
    NameSystem syntheticNames = new NameSystem();
    sink.write(", readTarget: ");
    printQualifiedNameOn(readTarget, sink, syntheticNames: syntheticNames);
    sink.write(", writeTarget: ");
    printQualifiedNameOn(writeTarget, sink, syntheticNames: syntheticNames);
  }
}

class KernelLoadLibraryGenerator extends KernelGenerator
    with LoadLibraryGenerator<Expression, Statement, Arguments> {
  final LoadLibraryBuilder builder;

  KernelLoadLibraryGenerator(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token,
      this.builder)
      : super(helper, token);

  @override
  Expression _makeRead(ShadowComplexAssignment complexAssignment) {
    var read =
        helper.makeStaticGet(builder.createTearoffMethod(helper.forest), token);
    complexAssignment?.read = read;
    return read;
  }

  @override
  Expression _makeWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    Expression write = makeInvalidWrite(value);
    write.fileOffset = offsetForToken(token);
    return write;
  }

  @override
  Expression doInvocation(int offset, Arguments arguments) {
    if (forest.argumentsPositional(arguments).length > 0 ||
        forest.argumentsNamed(arguments).length > 0) {
      helper.addProblemErrorIfConst(
          messageLoadLibraryTakesNoArguments, offset, 'loadLibrary'.length);
    }
    return builder.createLoadLibrary(offset, forest);
  }

  @override
  void printOn(StringSink sink) {
    sink.write(", builder: ");
    sink.write(builder);
  }
}

class KernelDeferredAccessGenerator extends KernelGenerator
    with DeferredAccessGenerator<Expression, Statement, Arguments> {
  @override
  final PrefixBuilder builder;

  @override
  final KernelGenerator generator;

  KernelDeferredAccessGenerator(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token,
      this.builder,
      this.generator)
      : super(helper, token);

  @override
  Expression _makeSimpleRead() {
    return helper.wrapInDeferredCheck(
        generator._makeSimpleRead(), builder, token.charOffset);
  }

  @override
  Expression _makeRead(ShadowComplexAssignment complexAssignment) {
    return helper.wrapInDeferredCheck(
        generator._makeRead(complexAssignment), builder, token.charOffset);
  }

  @override
  Expression _makeWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    return helper.wrapInDeferredCheck(
        generator._makeWrite(value, voidContext, complexAssignment),
        builder,
        token.charOffset);
  }
}

class KernelTypeUseGenerator extends KernelReadOnlyAccessGenerator
    with TypeUseGenerator<Expression, Statement, Arguments> {
  /// The import prefix preceding the [declaration] reference, or `null` if
  /// the reference is not prefixed.
  @override
  final PrefixBuilder prefix;

  /// The offset at which the [declaration] is referenced by this generator,
  /// or `-1` if the reference is implicit.
  @override
  final int declarationReferenceOffset;

  @override
  final TypeDeclarationBuilder declaration;

  KernelTypeUseGenerator(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token,
      this.prefix,
      this.declarationReferenceOffset,
      this.declaration,
      String plainNameForRead)
      : super(helper, token, null, plainNameForRead);

  @override
  Expression get expression {
    if (super.expression == null) {
      int offset = offsetForToken(token);
      if (declaration is KernelInvalidTypeBuilder) {
        KernelInvalidTypeBuilder declaration = this.declaration;
        helper.addProblemErrorIfConst(
            declaration.message.messageObject, offset, token.length);
        super.expression = new ShadowSyntheticExpression(
            new Throw(forest.literalString(declaration.message.message, token))
              ..fileOffset = offset);
      } else {
        super.expression = forest.literalType(
            buildTypeWithBuiltArguments(null, nonInstanceAccessIsError: true),
            token);
      }
    }
    return super.expression;
  }

  @override
  Expression makeInvalidWrite(Expression value) {
    return buildThrowNoSuchMethodError(
        forest.literalNull(token),
        storeOffset(
            forest.arguments(<Expression>[value], null), value.fileOffset),
        isSetter: true);
  }

  @override
  buildPropertyAccess(
      IncompleteSendGenerator send, int operatorOffset, bool isNullAware) {
    // `SomeType?.toString` is the same as `SomeType.toString`, not
    // `(SomeType).toString`.
    isNullAware = false;

    Name name = send.name;
    Arguments arguments = send.arguments;

    if (declaration is KernelClassBuilder) {
      KernelClassBuilder declaration = this.declaration;
      Declaration member = declaration.findStaticBuilder(
          name.name, offsetForToken(token), uri, helper.library);

      Generator generator;
      if (member == null) {
        // If we find a setter, [member] is an [AccessErrorBuilder], not null.
        if (send is IncompletePropertyAccessGenerator) {
          generator = new UnresolvedNameGenerator(helper, send.token, name);
        } else {
          return helper.buildConstructorInvocation(declaration, send.token,
              arguments, name.name, null, token.charOffset, Constness.implicit);
        }
      } else {
        Declaration setter;
        if (member.isSetter) {
          setter = member;
        } else if (member.isGetter) {
          setter = declaration.findStaticBuilder(
              name.name, offsetForToken(token), uri, helper.library,
              isSetter: true);
        } else if (member.isField && !member.isFinal) {
          setter = member;
        }
        generator = new StaticAccessGenerator<Expression, Statement,
            Arguments>.fromBuilder(helper, member, send.token, setter);
      }

      return arguments == null
          ? generator
          : generator.doInvocation(offsetForToken(send.token), arguments);
    } else {
      return super.buildPropertyAccess(send, operatorOffset, isNullAware);
    }
  }

  @override
  Expression doInvocation(int offset, Arguments arguments) {
    return helper.buildConstructorInvocation(declaration, token, arguments, "",
        null, token.charOffset, Constness.implicit);
  }
}

class KernelReadOnlyAccessGenerator extends KernelGenerator
    with ReadOnlyAccessGenerator<Expression, Statement, Arguments> {
  @override
  final String plainNameForRead;

  Expression expression;

  VariableDeclaration value;

  KernelReadOnlyAccessGenerator(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token,
      this.expression,
      this.plainNameForRead)
      : super(helper, token);

  @override
  Expression _makeSimpleRead() => expression;

  @override
  Expression _makeRead(ShadowComplexAssignment complexAssignment) {
    value ??= new VariableDeclaration.forValue(expression);
    return new VariableGet(value);
  }

  @override
  Expression _makeWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    var write = makeInvalidWrite(value);
    complexAssignment?.write = write;
    return write;
  }

  @override
  Expression _finish(
          Expression body, ShadowComplexAssignment complexAssignment) =>
      super._finish(makeLet(value, body), complexAssignment);

  @override
  Expression doInvocation(int offset, Arguments arguments) {
    return helper.buildMethodInvocation(buildSimpleRead(), callName, arguments,
        adjustForImplicitCall(plainNameForRead, offset),
        isImplicitCall: true);
  }

  @override
  void printOn(StringSink sink) {
    NameSystem syntheticNames = new NameSystem();
    sink.write(", expression: ");
    printNodeOn(expression, sink, syntheticNames: syntheticNames);
    sink.write(", plainNameForRead: ");
    sink.write(plainNameForRead);
    sink.write(", value: ");
    printNodeOn(value, sink, syntheticNames: syntheticNames);
  }
}

class KernelLargeIntAccessGenerator extends KernelGenerator
    with LargeIntAccessGenerator<Expression, Statement, Arguments> {
  KernelLargeIntAccessGenerator(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token)
      : super(helper, token);

  @override
  Expression _makeSimpleRead() => buildError();

  @override
  Expression _makeSimpleWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    return buildError();
  }

  @override
  Expression _makeRead(ShadowComplexAssignment complexAssignment) {
    return buildError();
  }

  @override
  Expression _makeWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    return buildError();
  }
}

class KernelUnresolvedNameGenerator extends KernelGenerator
    with
        ErroneousExpressionGenerator<Expression, Statement, Arguments>,
        UnresolvedNameGenerator<Expression, Statement, Arguments> {
  @override
  final Name name;

  KernelUnresolvedNameGenerator(
      ExpressionGeneratorHelper<dynamic, dynamic, dynamic> helper,
      Token token,
      this.name)
      : super(helper, token);

  @override
  Expression _makeRead(ShadowComplexAssignment complexAssignment) {
    return unsupported("_makeRead", offsetForToken(token), uri);
  }

  @override
  Expression _makeWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    return unsupported("_makeWrite", offsetForToken(token), uri);
  }

  @override
  void printOn(StringSink sink) {
    sink.write(", name: ");
    sink.write(name.name);
  }
}

class KernelUnlinkedGenerator extends KernelGenerator
    with UnlinkedGenerator<Expression, Statement, Arguments> {
  @override
  final UnlinkedDeclaration declaration;

  final Expression receiver;

  final Name name;

  KernelUnlinkedGenerator(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token,
      this.declaration)
      : name = new Name(declaration.name, helper.library.target),
        receiver = new InvalidExpression(declaration.name)
          ..fileOffset = offsetForToken(token),
        super(helper, token);

  @override
  Expression _makeRead(ShadowComplexAssignment complexAssignment) {
    return unsupported("_makeRead", offsetForToken(token), uri);
  }

  @override
  Expression _makeWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    return unsupported("_makeWrite", offsetForToken(token), uri);
  }

  @override
  Expression buildAssignment(Expression value, {bool voidContext}) {
    return new PropertySet(receiver, name, value)
      ..fileOffset = offsetForToken(token);
  }

  @override
  Expression buildSimpleRead() {
    return new PropertyGetJudgment(receiver, name)
      ..fileOffset = offsetForToken(token);
  }

  @override
  Expression doInvocation(int offset, Arguments arguments) {
    return unsupported("doInvocation", offset, uri);
  }
}

abstract class KernelContextAwareGenerator extends KernelGenerator
    with ContextAwareGenerator<Expression, Statement, Arguments> {
  @override
  final Generator<Expression, Statement, Arguments> generator;

  KernelContextAwareGenerator(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token,
      this.generator)
      : super(helper, token);

  @override
  Expression _makeRead(ShadowComplexAssignment complexAssignment) {
    return unsupported("_makeRead", offsetForToken(token), uri);
  }

  @override
  Expression _makeWrite(Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    return unsupported("_makeWrite", offsetForToken(token), uri);
  }
}

class KernelDelayedAssignment extends KernelContextAwareGenerator
    with DelayedAssignment<Expression, Statement, Arguments> {
  @override
  final Expression value;

  @override
  String assignmentOperator;

  KernelDelayedAssignment(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token,
      Generator<Expression, Statement, Arguments> generator,
      this.value,
      this.assignmentOperator)
      : super(helper, token, generator);

  @override
  void printOn(StringSink sink) {
    sink.write(", value: ");
    printNodeOn(value, sink);
    sink.write(", assignmentOperator: ");
    sink.write(assignmentOperator);
  }
}

class KernelDelayedPostfixIncrement extends KernelContextAwareGenerator
    with DelayedPostfixIncrement<Expression, Statement, Arguments> {
  @override
  final Name binaryOperator;

  @override
  final Procedure interfaceTarget;

  KernelDelayedPostfixIncrement(
      ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
      Token token,
      Generator<Expression, Statement, Arguments> generator,
      this.binaryOperator,
      this.interfaceTarget)
      : super(helper, token, generator);
}

Expression makeLet(VariableDeclaration variable, Expression body) {
  if (variable == null) return body;
  return new Let(variable, body);
}

Expression makeBinary(
    Expression left,
    Name operator,
    Procedure interfaceTarget,
    Expression right,
    ExpressionGeneratorHelper<Expression, Statement, Arguments> helper,
    {int offset: TreeNode.noOffset}) {
  return new ShadowMethodInvocation(
      left,
      operator,
      helper.storeOffset(
          helper.forest.castArguments(
              helper.forest.arguments(<Expression>[right], null)),
          offset),
      interfaceTarget: interfaceTarget)
    ..fileOffset = offset;
}

Expression buildIsNull(Expression value, int offset,
    ExpressionGeneratorHelper<dynamic, dynamic, dynamic> helper) {
  return makeBinary(value, equalsName, null,
      helper.storeOffset(helper.forest.literalNull(null), offset), helper,
      offset: offset);
}

VariableDeclaration makeOrReuseVariable(Expression value) {
  // TODO: Devise a way to remember if a variable declaration was reused
  // or is fresh (hence needs a let binding).
  return new VariableDeclaration.forValue(value);
}

int adjustForImplicitCall(String name, int offset) {
  // Normally the offset is at the start of the token, but in this case,
  // because we insert a '.call', we want it at the end instead.
  return offset + (name?.length ?? 0);
}

bool isFieldOrGetter(Member member) {
  return member is Field || (member is Procedure && member.isGetter);
}