pkg/front_end/lib/src/fasta/kernel/expression_generator.dart

// Copyright (c) 2016, 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.

/// A library to help transform compounds and null-aware accessors into
/// let expressions.
library fasta.expression_generator;

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

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

import '../fasta_codes.dart'
    show
        LocatedMessage,
        messageInvalidInitializer,
        messageLoadLibraryTakesNoArguments,
        messageSuperAsExpression,
        templateDeferredTypeAnnotation,
        templateIntegerLiteralIsOutOfRange,
        templateNotAPrefixInTypeAnnotation,
        templateNotAType,
        templateUnresolvedPrefixInTypeAnnotation;

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

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

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

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

import '../scope.dart' show AccessErrorBuilder, ProblemBuilder, Scope;

import '../type_inference/type_promotion.dart' show TypePromoter;

import 'body_builder.dart' show Identifier, noLocation;

import 'constness.dart' show Constness;

import 'forest.dart' show Forest;

import 'kernel_builder.dart' show LoadLibraryBuilder, PrefixBuilder;

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

import 'kernel_ast_api.dart'
    show
        Constructor,
        DartType,
        Field,
        FunctionNode,
        FunctionType,
        Initializer,
        InvalidType,
        Let,
        Member,
        Name,
        Procedure,
        PropertySet,
        ShadowComplexAssignment,
        ShadowIllegalAssignment,
        ShadowIndexAssign,
        ShadowMethodInvocation,
        ShadowNullAwarePropertyGet,
        ShadowPropertyAssign,
        ShadowPropertyGet,
        ShadowStaticAssignment,
        ShadowSuperMethodInvocation,
        ShadowSuperPropertyGet,
        ShadowVariableAssignment,
        ShadowVariableDeclaration,
        ShadowVariableGet,
        StaticGet,
        StaticSet,
        SuperMethodInvocation,
        SuperPropertySet,
        Throw,
        TreeNode,
        TypeParameter,
        TypeParameterType,
        VariableDeclaration,
        VariableGet,
        VariableSet;

import 'kernel_ast_api.dart' as kernel show Expression, Node, Statement;

import 'kernel_builder.dart'
    show
        Builder,
        BuiltinTypeBuilder,
        FunctionTypeAliasBuilder,
        KernelClassBuilder,
        KernelFunctionTypeAliasBuilder,
        KernelInvalidTypeBuilder,
        KernelPrefixBuilder,
        KernelTypeVariableBuilder,
        LibraryBuilder,
        LoadLibraryBuilder,
        PrefixBuilder,
        TypeDeclarationBuilder;

part 'expression_generator_impl.dart';

/// An [Accessor] represents a subexpression for which we can't yet build a
/// kernel [kernel.Expression] because we don't yet know the context in which
/// it is used.
///
/// Once the context is known, an [Accessor] can be converted into an
/// [kernel.Expression] by calling a "build" method.
///
/// For example, when building a kernel representation for `a[x] = b`, after
/// parsing `a[x]` but before parsing `= b`, we don't yet know whether to
/// generate an invocation of `operator[]` or `operator[]=`, so we generate an
/// [Accessor] object.  Later, after `= b` is parsed, [buildAssignment] will be
/// called.
// TODO(ahe): Move this into [Generator] when all uses have been updated.
abstract class Accessor<Arguments> {
  final BuilderHelper<dynamic, dynamic, Arguments> helper;
  final Token token;

  Accessor(this.helper, this.token);

  Forest<kernel.Expression, kernel.Statement, Token, Arguments> get forest =>
      helper.forest;

  /// Builds an [kernel.Expression] representing a read from the accessor.
  kernel.Expression buildSimpleRead() {
    return _finish(_makeSimpleRead(), null);
  }

  /// Builds an [kernel.Expression] representing an assignment with the
  /// accessor on the LHS and [value] on the RHS.
  ///
  /// The returned expression evaluates to the assigned value, unless
  /// [voidContext] is true, in which case it may evaluate to anything.
  kernel.Expression buildAssignment(kernel.Expression value,
      {bool voidContext: false}) {
    var complexAssignment = startComplexAssignment(value);
    return _finish(_makeSimpleWrite(value, voidContext, complexAssignment),
        complexAssignment);
  }

  /// Returns an [kernel.Expression] representing a null-aware assignment
  /// (`??=`) with the accessor on the LHS and [value] on the RHS.
  ///
  /// The returned expression evaluates to the assigned value, unless
  /// [voidContext] is true, in which case it may evaluate to anything.
  ///
  /// [type] is the static type of the RHS.
  kernel.Expression buildNullAwareAssignment(
      kernel.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);
  }

  /// Returns an [kernel.Expression] representing a compound assignment
  /// (e.g. `+=`) with the accessor on the LHS and [value] on the RHS.
  kernel.Expression buildCompoundAssignment(
      Name binaryOperator, kernel.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);
  }

  /// Returns an [kernel.Expression] representing a pre-increment or
  /// pre-decrement of the accessor.
  kernel.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);
  }

  /// Returns an [kernel.Expression] representing a post-increment or
  /// post-decrement of the accessor.
  kernel.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 ShadowVariableDeclaration.forValue(
        _makeWrite(combiner, true, complexAssignment),
        helper.functionNestingLevel);
    return _finish(
        makeLet(value, makeLet(dummy, valueAccess())), complexAssignment);
  }

  kernel.Expression _makeSimpleRead() => _makeRead(null);

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

  kernel.Expression _makeRead(ShadowComplexAssignment complexAssignment);

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

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

  /// Returns an [kernel.Expression] representing a compile-time error.
  ///
  /// At runtime, an exception will be thrown.
  makeInvalidRead() {
    return unhandled("compile-time error", "$runtimeType",
        offsetForToken(token), helper.uri);
  }

  /// Returns an [kernel.Expression] representing a compile-time error wrapping
  /// [value].
  ///
  /// At runtime, [value] will be evaluated before throwing an exception.
  makeInvalidWrite(kernel.Expression value) {
    return unhandled("compile-time error", "$runtimeType",
        offsetForToken(token), helper.uri);
  }

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

// TODO(ahe): Merge classes [Accessor] and [FastaAccessor] into this.
abstract class Generator<Arguments> = Accessor<Arguments>
    with FastaAccessor<Arguments>;

class VariableUseGenerator<Arguments> extends Generator<Arguments> {
  final VariableDeclaration variable;

  final DartType promotedType;

  VariableUseGenerator(BuilderHelper<dynamic, dynamic, Arguments> helper,
      Token token, this.variable,
      [this.promotedType])
      : super(helper, token);

  String get plainNameForRead => variable.name;

  String get debugName => "VariableUseGenerator";

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

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

  @override
  ShadowComplexAssignment startComplexAssignment(kernel.Expression rhs) =>
      new ShadowVariableAssignment(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 PropertyAccessGenerator<Arguments> extends Generator<Arguments> {
  final kernel.Expression receiver;

  final Name name;

  final Member getter;

  final Member setter;

  VariableDeclaration _receiverVariable;

  PropertyAccessGenerator.internal(
      BuilderHelper<dynamic, dynamic, Arguments> helper,
      Token token,
      this.receiver,
      this.name,
      this.getter,
      this.setter)
      : super(helper, token);

  static FastaAccessor<Arguments> make<Arguments>(
      BuilderHelper<dynamic, dynamic, Arguments> helper,
      Token token,
      kernel.Expression receiver,
      Name name,
      Member getter,
      Member setter,
      bool isNullAware) {
    if (helper.forest.isThisExpression(receiver)) {
      return unsupported("ThisExpression", offsetForToken(token), helper.uri);
    } else {
      return isNullAware
          ? new NullAwarePropertyAccessGenerator(
              helper, token, receiver, name, getter, setter, null)
          : new PropertyAccessGenerator.internal(
              helper, token, receiver, name, getter, setter);
    }
  }

  String get plainNameForRead => name.name;

  String get debugName => "PropertyAccessGenerator";

  bool get isThisPropertyAccess => forest.isThisExpression(receiver);

  kernel.Expression _makeSimpleRead() =>
      new ShadowPropertyGet(receiver, name, getter)
        ..fileOffset = offsetForToken(token);

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

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

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

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

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

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

  @override
  ShadowComplexAssignment startComplexAssignment(kernel.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);
  }
}

/// Special case of [PropertyAccessGenerator] to avoid creating an indirect
/// access to 'this'.
class ThisPropertyAccessGenerator<Arguments> extends Generator<Arguments> {
  final Name name;

  final Member getter;

  final Member setter;

  ThisPropertyAccessGenerator(BuilderHelper<dynamic, dynamic, Arguments> helper,
      Token token, this.name, this.getter, this.setter)
      : super(helper, token);

  String get plainNameForRead => name.name;

  String get debugName => "ThisPropertyAccessGenerator";

  bool get isThisPropertyAccess => true;

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

  kernel.Expression _makeWrite(kernel.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;
  }

  kernel.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(kernel.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 NullAwarePropertyAccessGenerator<Arguments> extends Generator<Arguments> {
  final VariableDeclaration receiver;

  final kernel.Expression receiverExpression;

  final Name name;

  final Member getter;

  final Member setter;

  final DartType type;

  NullAwarePropertyAccessGenerator(
      BuilderHelper<dynamic, dynamic, Arguments> helper,
      Token token,
      this.receiverExpression,
      this.name,
      this.getter,
      this.setter,
      this.type)
      : this.receiver = makeOrReuseVariable(receiverExpression),
        super(helper, token);

  String get plainNameForRead => name.name;

  String get debugName => "NullAwarePropertyAccessGenerator";

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

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

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

  kernel.Expression _finish(
      kernel.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 ShadowNullAwarePropertyGet(receiver, nullAwareGuard)
        ..fileOffset = offset;
    }
  }

  kernel.Expression doInvocation(int offset, Arguments arguments) {
    return unimplemented("doInvocation", offset, uri);
  }

  @override
  ShadowComplexAssignment startComplexAssignment(kernel.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 SuperPropertyAccessGenerator<Arguments> extends Generator<Arguments> {
  final Name name;

  final Member getter;

  final Member setter;

  SuperPropertyAccessGenerator(
      BuilderHelper<dynamic, dynamic, Arguments> helper,
      Token token,
      this.name,
      this.getter,
      this.setter)
      : super(helper, token);

  String get plainNameForRead => name.name;

  String get debugName => "SuperPropertyAccessGenerator";

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

  kernel.Expression _makeWrite(kernel.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;
  }

  kernel.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(kernel.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 IndexedAccessGenerator<Arguments> extends Generator<Arguments> {
  final kernel.Expression receiver;

  final kernel.Expression index;

  final Procedure getter;

  final Procedure setter;

  VariableDeclaration receiverVariable;

  VariableDeclaration indexVariable;

  IndexedAccessGenerator.internal(
      BuilderHelper<dynamic, dynamic, Arguments> helper,
      Token token,
      this.receiver,
      this.index,
      this.getter,
      this.setter)
      : super(helper, token);

  static FastaAccessor<Arguments> make<Arguments>(
      BuilderHelper<dynamic, dynamic, Arguments> helper,
      Token token,
      kernel.Expression receiver,
      kernel.Expression index,
      Procedure getter,
      Procedure setter) {
    if (helper.forest.isThisExpression(receiver)) {
      return new ThisIndexedAccessGenerator(
          helper, token, index, getter, setter);
    } else {
      return new IndexedAccessGenerator.internal(
          helper, token, receiver, index, getter, setter);
    }
  }

  String get plainNameForRead => "[]";

  String get plainNameForWrite => "[]=";

  String get debugName => "IndexedAccessGenerator";

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

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

  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);
  }

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

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

  kernel.Expression _makeWrite(kernel.Expression value, bool voidContext,
      ShadowComplexAssignment complexAssignment) {
    if (!voidContext) return _makeWriteAndReturn(value, complexAssignment);
    var write = new ShadowMethodInvocation(
        receiverAccess(),
        indexSetName,
        forest.castArguments(
            forest.arguments(<kernel.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.
  _makeWriteAndReturn(
      kernel.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(
            <kernel.Expression>[indexAccess(), new VariableGet(valueVariable)],
            token)),
        interfaceTarget: setter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    var dummy = new ShadowVariableDeclaration.forValue(
        write, helper.functionNestingLevel);
    return makeLet(
        valueVariable, makeLet(dummy, new VariableGet(valueVariable)));
  }

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

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

  @override
  ShadowComplexAssignment startComplexAssignment(kernel.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);
  }
}

/// Special case of [IndexedAccessGenerator] to avoid creating an indirect
/// access to 'this'.
class ThisIndexedAccessGenerator<Arguments> extends Generator<Arguments> {
  final kernel.Expression index;

  final Procedure getter;

  final Procedure setter;

  VariableDeclaration indexVariable;

  ThisIndexedAccessGenerator(BuilderHelper<dynamic, dynamic, Arguments> helper,
      Token token, this.index, this.getter, this.setter)
      : super(helper, token);

  String get plainNameForRead => "[]";

  String get plainNameForWrite => "[]=";

  String get debugName => "ThisIndexedAccessGenerator";

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

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

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

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

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

  _makeWriteAndReturn(
      kernel.Expression value, ShadowComplexAssignment complexAssignment) {
    var valueVariable = new VariableDeclaration.forValue(value);
    var write = new ShadowMethodInvocation(
        forest.thisExpression(token),
        indexSetName,
        forest.castArguments(forest.arguments(
            <kernel.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)));
  }

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

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

  @override
  ShadowComplexAssignment startComplexAssignment(kernel.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 SuperIndexedAccessGenerator<Arguments> extends Generator<Arguments> {
  final kernel.Expression index;

  final Member getter;

  final Member setter;

  VariableDeclaration indexVariable;

  SuperIndexedAccessGenerator(BuilderHelper<dynamic, dynamic, Arguments> helper,
      Token token, this.index, this.getter, this.setter)
      : super(helper, token);

  String get plainNameForRead => "[]";

  String get plainNameForWrite => "[]=";

  String get debugName => "SuperIndexedAccessGenerator";

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

  kernel.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(<kernel.Expression>[index], token)),
        getter)
      ..fileOffset = offsetForToken(token);
  }

  kernel.Expression _makeSimpleWrite(kernel.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(<kernel.Expression>[index, value], token)),
        setter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    return write;
  }

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

  kernel.Expression _makeWrite(kernel.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(<kernel.Expression>[indexAccess(), value], token)),
        setter)
      ..fileOffset = offsetForToken(token);
    complexAssignment?.write = write;
    return write;
  }

  _makeWriteAndReturn(
      kernel.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(
            <kernel.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)));
  }

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

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

  @override
  ShadowComplexAssignment startComplexAssignment(kernel.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 StaticAccessGenerator<Arguments> extends Generator<Arguments> {
  final Member readTarget;

  final Member writeTarget;

  StaticAccessGenerator(BuilderHelper<dynamic, dynamic, Arguments> helper,
      Token token, this.readTarget, this.writeTarget)
      : assert(readTarget != null || writeTarget != null),
        super(helper, token);

  factory StaticAccessGenerator.fromBuilder(
      BuilderHelper<dynamic, dynamic, Arguments> helper,
      Builder builder,
      Token token,
      Builder builderSetter) {
    if (builder is AccessErrorBuilder) {
      AccessErrorBuilder error = builder;
      builder = error.builder;
      // We should only see an access error here if we've looked up a setter
      // when not explicitly looking for a setter.
      assert(builder.isSetter);
    } else if (builder.target == null) {
      return unhandled(
          "${builder.runtimeType}",
          "StaticAccessGenerator.fromBuilder",
          offsetForToken(token),
          helper.uri);
    }
    Member getter = builder.target.hasGetter ? builder.target : null;
    Member setter = builder.target.hasSetter ? builder.target : null;
    if (setter == null) {
      if (builderSetter?.target?.hasSetter ?? false) {
        setter = builderSetter.target;
      }
    }
    return new StaticAccessGenerator(helper, token, getter, setter);
  }

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

  String get debugName => "StaticAccessGenerator";

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

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

  kernel.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(kernel.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 LoadLibraryGenerator<Arguments> extends Generator<Arguments> {
  final LoadLibraryBuilder builder;

  LoadLibraryGenerator(BuilderHelper<dynamic, dynamic, Arguments> helper,
      Token token, this.builder)
      : super(helper, token);

  String get plainNameForRead => 'loadLibrary';

  String get debugName => "LoadLibraryGenerator";

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

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

  kernel.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 DeferredAccessGenerator<Arguments> extends Generator<Arguments> {
  final PrefixBuilder builder;

  final FastaAccessor accessor;

  DeferredAccessGenerator(BuilderHelper<dynamic, dynamic, Arguments> helper,
      Token token, this.builder, this.accessor)
      : super(helper, token);

  String get plainNameForRead {
    return unsupported(
        "deferredAccessor.plainNameForRead", offsetForToken(token), uri);
  }

  String get debugName => "DeferredAccessGenerator";

  kernel.Expression _makeSimpleRead() {
    return helper.wrapInDeferredCheck(
        accessor._makeSimpleRead(), builder, token.charOffset);
  }

  kernel.Expression _makeRead(ShadowComplexAssignment complexAssignment) {
    return helper.wrapInDeferredCheck(
        accessor._makeRead(complexAssignment), builder, token.charOffset);
  }

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

  buildPropertyAccess(
      IncompleteSend send, int operatorOffset, bool isNullAware) {
    var propertyAccess =
        accessor.buildPropertyAccess(send, operatorOffset, isNullAware);
    if (propertyAccess is FastaAccessor) {
      return new DeferredAccessGenerator(
          helper, token, builder, propertyAccess);
    } else {
      kernel.Expression expression = propertyAccess;
      return helper.wrapInDeferredCheck(expression, builder, token.charOffset);
    }
  }

  @override
  DartType buildTypeWithBuiltArguments(List<DartType> arguments,
      {bool nonInstanceAccessIsError: false}) {
    helper.addProblem(
        templateDeferredTypeAnnotation.withArguments(
            accessor.buildTypeWithBuiltArguments(arguments,
                nonInstanceAccessIsError: nonInstanceAccessIsError),
            builder.name),
        offsetForToken(token),
        lengthForToken(token));
    return const InvalidType();
  }

  kernel.Expression doInvocation(int offset, Arguments arguments) {
    return helper.wrapInDeferredCheck(
        accessor.doInvocation(offset, arguments), builder, token.charOffset);
  }

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

abstract class _ReadOnlyAccessor<Arguments> extends Accessor<Arguments> {
  kernel.Expression expression;
  VariableDeclaration value;

  _ReadOnlyAccessor(BuilderHelper<dynamic, dynamic, Arguments> helper,
      this.expression, Token token)
      : super(helper, token);

  kernel.Expression _makeSimpleRead() => expression;

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

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

  kernel.Expression _finish(
          kernel.Expression body, ShadowComplexAssignment complexAssignment) =>
      super._finish(makeLet(value, body), complexAssignment);
}

abstract class _DelayedErrorAccessor<Arguments> extends Accessor<Arguments> {
  _DelayedErrorAccessor(
      BuilderHelper<dynamic, dynamic, Arguments> helper, Token token)
      : super(helper, token);

  kernel.Expression buildError();

  kernel.Expression _makeSimpleRead() => buildError();
  kernel.Expression _makeSimpleWrite(kernel.Expression value, bool voidContext,
          ShadowComplexAssignment complexAssignment) =>
      buildError();
  kernel.Expression _makeRead(ShadowComplexAssignment complexAssignment) =>
      buildError();
  kernel.Expression _makeWrite(kernel.Expression value, bool voidContext,
          ShadowComplexAssignment complexAssignment) =>
      buildError();
}

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

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

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

VariableDeclaration makeOrReuseVariable(kernel.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);
}