pkg/front_end/lib/src/fasta/kernel/kernel_helper.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.

library fasta.kernel_target;

import 'package:kernel/ast.dart';
import 'package:kernel/clone.dart' show CloneVisitorNotMembers;
import 'package:kernel/type_algebra.dart' show Substitution;

/// Data for clone default values for synthesized function nodes once the
/// original default values have been computed.
///
/// This is used for constructors in unnamed mixin application, which are
/// created from the constructors in the superclass, and for tear off lowerings
/// for redirecting factories, which are created from the effective target
/// constructor.
class SynthesizedFunctionNode {
  /// Type parameter map from type parameters in scope [_original] to types
  /// in scope of [_synthesized].
  // TODO(johnniwinther): Is this ever needed? Should occurrence of type
  //  variable types in default values be a compile time error?
  final Map<TypeParameter, DartType> _typeSubstitution;

  /// The original function node.
  final FunctionNode _original;

  /// The synthesized function node.
  final FunctionNode _synthesized;

  /// If `true`, the [_synthesized] is guaranteed to have the same parameters in
  /// the same order as [_original]. Otherwise [_original] is only guaranteed to
  /// be callable from [_synthesized], meaning that is has at most the same
  /// number of positional parameters and a, possibly reordered, subset of the
  /// named parameters.
  final bool identicalSignatures;

  SynthesizedFunctionNode(
      this._typeSubstitution, this._original, this._synthesized,
      {this.identicalSignatures: true});

  void cloneDefaultValues() {
    // TODO(ahe): It is unclear if it is legal to use type variables in
    // default values, but Fasta is currently allowing it, and the VM
    // accepts it. If it isn't legal, the we can speed this up by using a
    // single cloner without substitution.
    CloneVisitorNotMembers? cloner;

    void cloneInitializer(VariableDeclaration originalParameter,
        VariableDeclaration clonedParameter) {
      if (originalParameter.initializer != null) {
        cloner ??=
            new CloneVisitorNotMembers(typeSubstitution: _typeSubstitution);
        clonedParameter.initializer = cloner!
            .clone(originalParameter.initializer!)
              ..parent = clonedParameter;
      }
    }

    // For mixin application constructors, the argument count is the same, but
    // for redirecting tear off lowerings, the argument count of the tear off
    // can be less than that of the redirection target.

    assert(_synthesized.positionalParameters.length <=
        _original.positionalParameters.length);
    for (int i = 0; i < _synthesized.positionalParameters.length; i++) {
      cloneInitializer(_original.positionalParameters[i],
          _synthesized.positionalParameters[i]);
    }

    if (identicalSignatures) {
      assert(_synthesized.namedParameters.length ==
          _original.namedParameters.length);
      for (int i = 0; i < _synthesized.namedParameters.length; i++) {
        cloneInitializer(
            _original.namedParameters[i], _synthesized.namedParameters[i]);
      }
    } else if (_synthesized.namedParameters.isNotEmpty) {
      Map<String, VariableDeclaration> originalParameters = {};
      for (int i = 0; i < _original.namedParameters.length; i++) {
        originalParameters[_original.namedParameters[i].name!] =
            _original.namedParameters[i];
      }
      for (int i = 0; i < _synthesized.namedParameters.length; i++) {
        cloneInitializer(
            originalParameters[_synthesized.namedParameters[i].name!]!,
            _synthesized.namedParameters[i]);
      }
    }
  }
}

class TypeDependency {
  final Member synthesized;
  final Member original;
  final Substitution substitution;

  TypeDependency(this.synthesized, this.original, this.substitution);

  void copyInferred() {
    for (int i = 0; i < original.function!.positionalParameters.length; i++) {
      VariableDeclaration synthesizedParameter =
          synthesized.function!.positionalParameters[i];
      VariableDeclaration constructorParameter =
          original.function!.positionalParameters[i];
      synthesizedParameter.type =
          substitution.substituteType(constructorParameter.type);
    }
    for (int i = 0; i < original.function!.namedParameters.length; i++) {
      VariableDeclaration synthesizedParameter =
          synthesized.function!.namedParameters[i];
      VariableDeclaration originalParameter =
          original.function!.namedParameters[i];
      synthesizedParameter.type =
          substitution.substituteType(originalParameter.type);
    }
    synthesized.function!.returnType =
        substitution.substituteType(original.function!.returnType);
  }
}