pkg/compiler/lib/src/ir/closure.dart

// 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' as ir;
// ignore: implementation_imports
import 'package:kernel/src/printer.dart' as ir;
import 'package:kernel/text/ast_to_text.dart' as ir show debugNodeToString;

/// Collection of scope data collected for a single member.
class ClosureScopeModel {
  /// Collection [ScopeInfo] data for the member.
  KernelScopeInfo? scopeInfo;

  /// Collected [CapturedScope] data for nodes.
  Map<ir.Node, KernelCapturedScope> capturedScopesMap =
      <ir.Node, KernelCapturedScope>{};

  /// Collected [ScopeInfo] data for nodes.
  Map<ir.LocalFunction, KernelScopeInfo> closuresToGenerate =
      <ir.LocalFunction, KernelScopeInfo>{};

  @override
  String toString() {
    return '$scopeInfo\n$capturedScopesMap\n$closuresToGenerate';
  }
}

class KernelScopeInfo {
  final Set<ir.Variable> localsUsedInTryOrSync;
  final bool hasThisLocal;
  final Set<ir.Variable> boxedVariables;
  // If boxedVariables is empty, this will be null, because no variables will
  // need to be boxed.
  final NodeBox? capturedVariablesAccessor;

  /// The set of variables that were defined in another scope, but are used in
  /// this scope. The items in this set are either of type VariableDeclaration
  /// or TypeParameterTypeWithContext.
  Set<ir.Node /* VariableDeclaration | TypeParameterTypeWithContext */>
  freeVariables = <ir.Node>{};

  /// A set of type parameters that are defined in another scope and are only
  /// used if runtime type information is checked. If runtime type information
  /// needs to be retained, all of these type variables will be added ot the
  /// freeVariables set. Whether these variables are actually used as
  /// freeVariables will be set by the time this structure is converted to a
  /// JsScopeInfo, so JsScopeInfo does not need to use them.
  Map<TypeVariableTypeWithContext, Set<VariableUse>> freeVariablesForRti =
      <TypeVariableTypeWithContext, Set<VariableUse>>{};

  /// If true, `this` is used as a free variable, in this scope. It is stored
  /// separately from [freeVariables] because there is no single
  /// `VariableDeclaration` node that represents `this`.
  bool thisUsedAsFreeVariable = false;

  /// If true, `this` is used as a free variable, in this scope if we are also
  /// performing runtime type checks. It is stored
  /// separately from [thisUsedAsFreeVariable] because we don't know at this
  /// stage if we will be needing type checks for this scope.
  Set<VariableUse> thisUsedAsFreeVariableIfNeedsRti = <VariableUse>{};

  KernelScopeInfo(this.hasThisLocal)
    : localsUsedInTryOrSync = <ir.Variable>{},
      boxedVariables = <ir.Variable>{},
      capturedVariablesAccessor = null;

  KernelScopeInfo.from(this.hasThisLocal, KernelScopeInfo info)
    : localsUsedInTryOrSync = info.localsUsedInTryOrSync,
      boxedVariables = info.boxedVariables,
      capturedVariablesAccessor = null;

  KernelScopeInfo.withBoxedVariables(
    this.boxedVariables,
    this.capturedVariablesAccessor,
    this.localsUsedInTryOrSync,
    this.freeVariables,
    this.freeVariablesForRti,
    this.thisUsedAsFreeVariable,
    this.thisUsedAsFreeVariableIfNeedsRti,
    this.hasThisLocal,
  );

  @override
  String toString() {
    StringBuffer sb = StringBuffer();
    sb.write('KernelScopeInfo(this=$hasThisLocal,');
    sb.write('freeVariables=$freeVariables,');
    sb.write('localsUsedInTryOrSync={${localsUsedInTryOrSync.join(', ')}}');
    String comma = '';
    sb.write('freeVariablesForRti={');
    freeVariablesForRti.forEach((key, value) {
      sb.write('$comma$key:$value');
      comma = ',';
    });
    sb.write('})');
    return sb.toString();
  }
}

class KernelCapturedScope extends KernelScopeInfo {
  KernelCapturedScope(
    super.boxedVariables,
    super.capturedVariablesAccessor,
    super.localsUsedInTryOrSync,
    super.freeVariables,
    super.freeVariablesForRti,
    super.thisUsedAsFreeVariable,
    super.thisUsedAsFreeVariableIfNeedsRti,
    super.hasThisLocal,
  ) : super.withBoxedVariables();

  // Loops through the free variables of an existing KernelCapturedScope and
  // creates a new KernelCapturedScope that only captures type variables.
  KernelCapturedScope.forSignature(KernelCapturedScope scope)
    : this(
        _empty,
        null,
        _empty,
        Set.of(scope.freeVariables.whereType<TypeVariableTypeWithContext>()),
        scope.freeVariablesForRti,
        scope.thisUsedAsFreeVariable,
        scope.thisUsedAsFreeVariableIfNeedsRti,
        scope.hasThisLocal,
      );

  // Silly hack because we don't have const sets.
  static final Set<ir.Variable> _empty = {};

  bool get requiresContextBox => boxedVariables.isNotEmpty;
}

class KernelCapturedLoopScope extends KernelCapturedScope {
  final List<ir.Variable> boxedLoopVariables;

  KernelCapturedLoopScope(
    Set<ir.Variable> boxedVariables,
    NodeBox? capturedVariablesAccessor,
    this.boxedLoopVariables,
    Set<ir.Variable> localsUsedInTryOrSync,
    Set<ir.Node /* VariableDeclaration | TypeVariableTypeWithContext */>
    freeVariables,
    Map<TypeVariableTypeWithContext, Set<VariableUse>> freeVariablesForRti,
    bool thisUsedAsFreeVariable,
    Set<VariableUse> thisUsedAsFreeVariableIfNeedsRti,
    bool hasThisLocal,
  ) : super(
        boxedVariables,
        capturedVariablesAccessor,
        localsUsedInTryOrSync,
        freeVariables,
        freeVariablesForRti,
        thisUsedAsFreeVariable,
        thisUsedAsFreeVariableIfNeedsRti,
        hasThisLocal,
      );

  bool get hasBoxedLoopVariables => boxedLoopVariables.isNotEmpty;
}

/// A local variable to disambiguate between a variable that has been captured
/// from one scope to another. This is the ir.Node version that corresponds to
/// [BoxLocal].
class NodeBox {
  final String name;
  final ir.TreeNode executableContext;
  NodeBox(this.name, this.executableContext);
}

sealed class VariableUse {}

enum SimpleVariableUse implements VariableUse {
  /// An explicit variable use.
  ///
  /// For type variable this is an explicit as-cast, an is-test or a type
  /// literal.
  explicit,

  /// A type variable used in the type of a local variable.
  localType,

  /// A type variable used in an implicit cast.
  implicitCast,

  /// A type variable passed as the type argument of a list literal.
  listLiteral,

  /// A type variable passed as the type argument of a set literal.
  setLiteral,

  /// A type variable passed as the type argument of a map literal.
  mapLiteral,

  /// A type variable in a field type.
  fieldType,
}

/// A type variable in a parameter type of a member.
class MemberParameterVariableUse implements VariableUse {
  final ir.Member member;

  MemberParameterVariableUse(this.member);

  @override
  int get hashCode => Object.hash(MemberParameterVariableUse, member);

  @override
  bool operator ==(other) {
    if (identical(this, other)) return true;
    if (other is! MemberParameterVariableUse) return false;
    return member == other.member;
  }

  @override
  String toString() => 'MemberParameterVariableUse(member=$member)';
}

/// A type variable in a parameter type of a local function.
class LocalParameterVariableUse implements VariableUse {
  final ir.LocalFunction localFunction;

  LocalParameterVariableUse(this.localFunction);

  @override
  int get hashCode => Object.hash(LocalParameterVariableUse, localFunction);

  @override
  bool operator ==(other) {
    if (identical(this, other)) return true;
    if (other is! LocalParameterVariableUse) return false;
    return localFunction == other.localFunction;
  }

  @override
  String toString() =>
      'LocalParameterVariableUse(localFunction=$localFunction)';
}

/// A type variable used in a return type of a member.
class MemberReturnTypeVariableUse implements VariableUse {
  final ir.Member member;

  MemberReturnTypeVariableUse(this.member);

  @override
  int get hashCode => Object.hash(MemberReturnTypeVariableUse, member);

  @override
  bool operator ==(other) {
    if (identical(this, other)) return true;
    if (other is! MemberReturnTypeVariableUse) return false;
    return member == other.member;
  }

  @override
  String toString() => 'MemberReturnTypeVariableUse(member=$member)';
}

/// A type variable used in a return type of a local function.
class LocalReturnTypeVariableUse implements VariableUse {
  final ir.LocalFunction localFunction;

  LocalReturnTypeVariableUse(this.localFunction);

  @override
  int get hashCode => Object.hash(LocalReturnTypeVariableUse, localFunction);

  @override
  bool operator ==(other) {
    if (identical(this, other)) return true;
    if (other is! LocalReturnTypeVariableUse) return false;
    return localFunction == other.localFunction;
  }

  @override
  String toString() =>
      'LocalReturnTypeVariableUse(localFunction=$localFunction)';
}

/// A type variable passed as a type argument to a constructor.
class ConstructorTypeArgumentVariableUse implements VariableUse {
  final ir.Member member;

  ConstructorTypeArgumentVariableUse(this.member);

  @override
  int get hashCode => Object.hash(ConstructorTypeArgumentVariableUse, member);

  @override
  bool operator ==(other) {
    if (identical(this, other)) return true;
    if (other is! ConstructorTypeArgumentVariableUse) return false;
    return member == other.member;
  }

  @override
  String toString() => 'ConstructorTypeArgumentVariableUse(member=$member)';
}

/// A type variable passed as a type argument to a static method.
class StaticTypeArgumentVariableUse implements VariableUse {
  final ir.Procedure procedure;

  StaticTypeArgumentVariableUse(this.procedure);

  @override
  int get hashCode => Object.hash(StaticTypeArgumentVariableUse, procedure);

  @override
  bool operator ==(other) {
    if (identical(this, other)) return true;
    if (other is! StaticTypeArgumentVariableUse) return false;
    return procedure == other.procedure;
  }

  @override
  String toString() => 'StaticTypeArgumentVariableUse(procedure=$procedure)';
}

/// A type variable passed as a type argument to an instance method.
class InstanceTypeArgumentVariableUse implements VariableUse {
  final ir.Expression invocation;

  InstanceTypeArgumentVariableUse(this.invocation);

  @override
  int get hashCode => Object.hash(InstanceTypeArgumentVariableUse, invocation);

  @override
  bool operator ==(other) {
    if (identical(this, other)) return true;
    if (other is! InstanceTypeArgumentVariableUse) return false;
    return invocation == other.invocation;
  }

  @override
  String toString() =>
      'InstanceTypeArgumentVariableUse(invocation=$invocation)';
}

/// A type variable passed as a type argument to a local function.
class LocalTypeArgumentVariableUse implements VariableUse {
  final ir.LocalFunction localFunction;
  final ir.Expression invocation;

  LocalTypeArgumentVariableUse(this.localFunction, this.invocation);

  @override
  int get hashCode =>
      Object.hash(LocalTypeArgumentVariableUse, localFunction, invocation);

  @override
  bool operator ==(other) {
    if (identical(this, other)) return true;
    if (other is! LocalTypeArgumentVariableUse) return false;
    return localFunction == other.localFunction &&
        invocation == other.invocation;
  }

  @override
  String toString() =>
      'LocalTypeArgumentVariableUse(localFunction=$localFunction,invocation=$invocation)';
}

/// A type argument of an generic instantiation.
class InstantiationTypeArgumentVariableUse implements VariableUse {
  final ir.Instantiation instantiation;

  InstantiationTypeArgumentVariableUse(this.instantiation);

  @override
  int get hashCode =>
      Object.hash(InstantiationTypeArgumentVariableUse, instantiation);

  @override
  bool operator ==(other) {
    if (identical(this, other)) return true;
    if (other is! InstantiationTypeArgumentVariableUse) return false;
    return instantiation == other.instantiation;
  }

  @override
  String toString() =>
      'InstantiationTypeArgumentVariableUse(instantiation=$instantiation)';
}

enum TypeVariableKind { cls, method, local }

/// A fake ir.Node that holds the TypeParameterType as well as the context in
/// which it occurs.
class TypeVariableTypeWithContext implements ir.Node {
  final ir.TreeNode? context;
  final ir.TypeParameterType type;
  final TypeVariableKind kind;
  final ir.TreeNode? typeDeclaration;

  /// [context] can be either an ir.Member or a ir.FunctionDeclaration or
  /// ir.FunctionExpression.
  factory TypeVariableTypeWithContext(
    ir.TypeParameterType type,
    ir.TreeNode? context,
  ) {
    TypeVariableKind kind;
    ir.GenericDeclaration? typeDeclaration = type.parameter.declaration;
    // TODO(fishythefish): Use exhaustive pattern switch.
    if (typeDeclaration is ir.Class) {
      // We have a class type variable, like `T` in `class Class<T> { ... }`.
      kind = TypeVariableKind.cls;
    } else if (typeDeclaration is ir.Procedure) {
      if (typeDeclaration.isFactory) {
        // We have a synthesized generic method type variable for a class type
        // variable.
        // TODO(johnniwinther): Handle constructor/factory type variables as
        // method type variables.
        kind = TypeVariableKind.cls;
        typeDeclaration = typeDeclaration.enclosingClass;
      } else {
        // We have a generic method type variable, like `T` in
        // `m<T>() { ... }`.
        kind = TypeVariableKind.method;
        context = typeDeclaration;
      }
    } else {
      // We have a generic local function type variable, like `T` in
      // `m() { local<T>() { ... } ... }`.
      assert(
        typeDeclaration is ir.LocalFunction,
        "Unexpected type declaration: $typeDeclaration",
      );
      kind = TypeVariableKind.local;
      context = typeDeclaration;
    }
    return TypeVariableTypeWithContext.internal(
      type,
      context,
      kind,
      typeDeclaration,
    );
  }

  TypeVariableTypeWithContext.internal(
    this.type,
    this.context,
    this.kind,
    this.typeDeclaration,
  );

  @override
  R accept<R>(ir.Visitor<R> v) {
    throw UnsupportedError('TypeVariableTypeWithContext.accept');
  }

  @override
  R accept1<R, A>(ir.Visitor1<R, A> v, A arg) {
    throw UnsupportedError('TypeVariableTypeWithContext.accept1');
  }

  @override
  Never visitChildren(ir.Visitor<Object?> v) {
    throw UnsupportedError('TypeVariableTypeWithContext.visitChildren');
  }

  @override
  int get hashCode => type.hashCode;

  @override
  bool operator ==(other) {
    if (other is! TypeVariableTypeWithContext) return false;
    return type == other.type && context == other.context;
  }

  @override
  String toString() => 'TypeVariableTypeWithContext(${toStringInternal()})';

  @override
  String toStringInternal() =>
      'type=${type.toStringInternal()},context=${context!.toStringInternal()},'
      'kind=$kind,typeDeclaration=${typeDeclaration!.toStringInternal()}';

  @override
  String toText(ir.AstTextStrategy strategy) => type.toText(strategy);

  @override
  void toTextInternal(ir.AstPrinter printer) => type.toTextInternal(printer);

  @override
  String leakingDebugToString() => ir.debugNodeToString(this);
}