pkg/front_end/lib/src/fasta/kernel/member_covariance.dart - sdk.git - Git at Google

 // 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 'dart:math';

 import 'package:kernel/ast.dart';

 /// Class that holds the covariant and generic-covariant-impl information for
 /// a member.
 // TODO(johnniwinther): Cache this in ClassMember.
 // TODO(johnniwinther): Maybe compact initial positional masks into a single
 //  int.
 class Covariance {
   static const int GenericCovariantImpl = 1;
   static const int Covariant = 2;

   /// Returns the covariance mask for [parameter].
   static int covarianceFromParameter(VariableDeclaration parameter) =>
       (parameter.isCovariantByDeclaration ? Covariant : 0) |
       (parameter.isCovariantByClass ? GenericCovariantImpl : 0);

   /// Returns the covariance mask for [field].
   static int covarianceFromField(Field field) =>
       (field.isCovariantByDeclaration ? Covariant : 0) |
       (field.isCovariantByClass ? GenericCovariantImpl : 0);

   /// Applies the [covariance] mask to [parameter].
   static void covarianceToParameter(
       int covariance, VariableDeclaration parameter) {
     if ((covariance & Covariant) != 0) {
       parameter.isCovariantByDeclaration = true;
     }
     if ((covariance & GenericCovariantImpl) != 0) {
       parameter.isCovariantByClass = true;
     }
   }

   /// Applies the [covariance] mask to parameter.
   static void covarianceToField(int covariance, Field field) {
     if ((covariance & Covariant) != 0) {
       field.isCovariantByDeclaration = true;
     }
     if ((covariance & GenericCovariantImpl) != 0) {
       field.isCovariantByClass = true;
     }
   }

   /// The covariance mask for the positional parameters.
   ///
   /// If no positional parameters have covariance, this is `null`.
   final List<int>? _positionalParameters;

   /// The covariance mask for the named parameters with name covariance.
   ///
   /// If no named parameters have covariance, this is `null`.
   final Map<String, int>? _namedParameters;

   /// The generic-covariant-impl state for the type parameters.
   ///
   /// If no type parameters are generic-covariant-impl, this is `null`.
   final List<bool>? _typeParameters;

   Covariance.internal(
       this._positionalParameters, this._namedParameters, this._typeParameters) {
     assert(_positionalParameters == null ||
         _positionalParameters.any((element) => element != 0));
     assert(_namedParameters == null ||
         _namedParameters.values.isNotEmpty &&
             _namedParameters.values.every((element) => element != 0));
     assert(
         _typeParameters == null || _typeParameters.any((element) => element));
   }

   /// The empty covariance.
   ///
   /// This is used for all members that do not use any covariance, regardless
   /// of parameter structure.
   const Covariance.empty()
       : _positionalParameters = null,
         _namedParameters = null,
         _typeParameters = null;

   /// Computes the covariance for the setter aspect of [field].
   ///
   /// The getter aspect of a field never uses covariance.
   factory Covariance.fromField(Field field) {
     int covariance = covarianceFromField(field);
     if (covariance == 0) {
       return const Covariance.empty();
     }
     return new Covariance.internal(<int>[covariance], null, null);
   }

   /// Computes the covariance for the [setter].
   factory Covariance.fromSetter(Procedure setter) {
     int covariance =
         covarianceFromParameter(setter.function.positionalParameters.first);
     if (covariance == 0) {
       return const Covariance.empty();
     }
     return new Covariance.internal(<int>[covariance], null, null);
   }

   /// Computes the covariance for the [procedure].
   factory Covariance.fromMethod(Procedure procedure) {
     FunctionNode function = procedure.function;
     List<int>? positionalParameters;
     if (function.positionalParameters.isNotEmpty) {
       for (int index = 0;
           index < function.positionalParameters.length;
           index++) {
         int covariance =
             covarianceFromParameter(function.positionalParameters[index]);
         if (covariance != 0) {
           positionalParameters ??=
               new List<int>.filled(function.positionalParameters.length, 0);
           positionalParameters[index] = covariance;
         }
       }
     }
     Map<String, int>? namedParameters;
     if (function.namedParameters.isNotEmpty) {
       for (int index = 0; index < function.namedParameters.length; index++) {
         VariableDeclaration parameter = function.namedParameters[index];
         int covariance = covarianceFromParameter(parameter);
         if (covariance != 0) {
           namedParameters ??= {};
           namedParameters[parameter.name!] = covariance;
         }
       }
     }
     List<bool>? typeParameters;
     if (function.typeParameters.isNotEmpty) {
       for (int index = 0; index < function.typeParameters.length; index++) {
         if (function.typeParameters[index].isCovariantByClass) {
           typeParameters ??=
               new List<bool>.filled(function.typeParameters.length, false);
           typeParameters[index] = true;
         }
       }
     }
     if (positionalParameters == null &&
         namedParameters == null &&
         typeParameters == null) {
       return const Covariance.empty();
     }
     return new Covariance.internal(
         positionalParameters, namedParameters, typeParameters);
   }

   /// Computes the covariance for [member].
   ///
   /// If [forSetter] is `true`, the covariance is computed for the setter
   /// aspect of [member]. Otherwise, the covariance for the getter/method aspect
   /// of [member] is computed.
   factory Covariance.fromMember(Member member, {required bool forSetter}) {
     if (member is Procedure) {
       if (member.kind == ProcedureKind.Getter) {
         return const Covariance.empty();
       } else if (member.kind == ProcedureKind.Setter) {
         return new Covariance.fromSetter(member);
       } else {
         return new Covariance.fromMethod(member);
       }
     } else if (member is Field) {
       if (forSetter) {
         return new Covariance.fromField(member);
       } else {
         return const Covariance.empty();
       }
     } else {
       throw new UnsupportedError(
           "Unexpected member $member (${member.runtimeType})");
     }
   }

   /// Returns `true` if this is the empty covariance.
   bool get isEmpty =>
       _positionalParameters == null &&
       _namedParameters == null &&
       _typeParameters == null;

   /// Returns the covariance mask for the [index]th positional parameter.
   int getPositionalVariance(int index) {
     List<int>? positionalParameters = _positionalParameters;
     return positionalParameters != null && index < positionalParameters.length
         ? positionalParameters[index]
         : 0;
   }

   /// Returns the covariance mask for the named parameter with the [name].
   int getNamedVariance(String name) {
     Map<String, int>? namedParameters = _namedParameters;
     return namedParameters != null ? (namedParameters[name] ?? 0) : 0;
   }

   /// Returns `true` if the [index]th type parameter is generic-covariant-impl.
   bool isTypeParameterGenericCovariantImpl(int index) {
     List<bool>? typeParameters = _typeParameters;
     return typeParameters != null && index < typeParameters.length
         ? typeParameters[index]
         : false;
   }

   /// Returns the merge of this covariance with [other] in which parameters are
   /// covariant if they are covariant in either this [Covariance] or [other].
   Covariance merge(Covariance other) {
     if (identical(this, other)) return this;
     List<int>? positionalParameters;
     if (_positionalParameters == null) {
       positionalParameters = other._positionalParameters;
     } else if (other._positionalParameters == null) {
       positionalParameters = _positionalParameters;
     } else {
       positionalParameters = new List<int>.filled(
           max(_positionalParameters.length, other._positionalParameters.length),
           0);
       for (int index = 0; index < positionalParameters.length; index++) {
         positionalParameters[index] =
             getPositionalVariance(index) | other.getPositionalVariance(index);
       }
     }
     Map<String, int>? namedParameters;
     if (_namedParameters == null) {
       namedParameters = other._namedParameters;
     } else if (other._namedParameters == null) {
       namedParameters = _namedParameters;
     } else {
       namedParameters = {};
       Set<String> names = {
         ..._namedParameters.keys,
         ...other._namedParameters.keys
       };
       for (String name in names) {
         namedParameters[name] =
             getNamedVariance(name) | other.getNamedVariance(name);
       }
     }
     List<bool>? typeParameters;
     if (_typeParameters == null) {
       typeParameters = other._typeParameters;
     } else if (other._typeParameters == null) {
       typeParameters = _typeParameters;
     } else {
       typeParameters = new List<bool>.filled(
           max(_typeParameters.length, other._typeParameters.length), false);
       for (int index = 0; index < typeParameters.length; index++) {
         typeParameters[index] = isTypeParameterGenericCovariantImpl(index) ||
             other.isTypeParameterGenericCovariantImpl(index);
       }
     }
     if (positionalParameters == null &&
         namedParameters == null &&
         typeParameters == null) {
       return const Covariance.empty();
     }
     return new Covariance.internal(
         positionalParameters, namedParameters, typeParameters);
   }

   /// Update [member] to have the covariant flags set with the covariance in
   /// this [Covariance].
   ///
   /// No covariance bits are removed from [member] during this process.
   void applyCovariance(Member member) {
     if (isEmpty) return;
     if (member is Procedure) {
       FunctionNode function = member.function;
       List<int>? positionalParameters = _positionalParameters;
       if (positionalParameters != null) {
         for (int index = 0; index < positionalParameters.length; index++) {
           if (index < function.positionalParameters.length) {
             covarianceToParameter(positionalParameters[index],
                 function.positionalParameters[index]);
           }
         }
       }
       if (_namedParameters != null) {
         for (VariableDeclaration parameter in function.namedParameters) {
           covarianceToParameter(getNamedVariance(parameter.name!), parameter);
         }
       }
       List<bool>? typeParameters = _typeParameters;
       if (typeParameters != null) {
         for (int index = 0; index < typeParameters.length; index++) {
           if (index < function.typeParameters.length) {
             if (typeParameters[index]) {
               function.typeParameters[index].isCovariantByClass = true;
             }
           }
         }
       }
     } else if (member is Field) {
       if (_positionalParameters != null) {
         covarianceToField(getPositionalVariance(0), member);
       }
     } else {
       throw new UnsupportedError(
           "Unexpected member $member (${member.runtimeType})");
     }
   }

   @override
   int get hashCode {
     int hash = 0;
     List<int>? positionalParameters = _positionalParameters;
     if (positionalParameters != null) {
       for (int covariance in positionalParameters) {
         hash += covariance.hashCode * 17;
       }
     }
     Map<String, int>? namedParameters = _namedParameters;
     if (namedParameters != null) {
       for (String name in namedParameters.keys) {
         hash += name.hashCode * 19 + namedParameters[name].hashCode * 23;
       }
     }
     List<bool>? typeParameters = _typeParameters;
     if (typeParameters != null) {
       for (bool covariance in typeParameters) {
         if (covariance) {
           hash += covariance.hashCode * 31;
         }
       }
     }
     return hash;
   }

   @override
   bool operator ==(Object other) {
     if (identical(this, other)) return true;
     if (other is Covariance) {
       if (_positionalParameters != other._positionalParameters) {
         if (_positionalParameters == null ||
             other._positionalParameters == null) {
           return false;
         }
         int positionalParameterCount = max(
             _positionalParameters.length, other._positionalParameters.length);
         for (int i = 0; i < positionalParameterCount; i++) {
           if (getPositionalVariance(i) != other.getPositionalVariance(i)) {
             return false;
           }
         }
       }
       if (_namedParameters != other._namedParameters) {
         if (_namedParameters == null || other._namedParameters == null) {
           return false;
         }
         Set<String> names = {
           ..._namedParameters.keys,
           ...other._namedParameters.keys
         };
         for (String name in names) {
           if (getNamedVariance(name) != other.getNamedVariance(name)) {
             return false;
           }
         }
       }
       if (_typeParameters != other._typeParameters) {
         if (_typeParameters == null || other._typeParameters == null) {
           return false;
         }
         int typeParameterCount =
             max(_typeParameters.length, other._typeParameters.length);
         for (int i = 0; i < typeParameterCount; i++) {
           if (isTypeParameterGenericCovariantImpl(i) !=
               other.isTypeParameterGenericCovariantImpl(i)) {
             return false;
           }
         }
       }
       return true;
     }
     return false;
   }

   @override
   String toString() {
     StringBuffer sb = new StringBuffer();
     if (isEmpty) {
       sb.write('Covariance.empty()');
     } else {
       sb.write('Covariance(');
       String comma = '';
       List<int>? positionalParameters = _positionalParameters;
       if (positionalParameters != null) {
         for (int index = 0; index < positionalParameters.length; index++) {
           if (positionalParameters[index] != 0) {
             sb.write(comma);
             sb.write('$index:');
             switch (positionalParameters[index]) {
               case GenericCovariantImpl:
                 sb.write('GenericCovariantImpl');
                 break;
               case Covariant:
                 sb.write('Covariant');
                 break;
               default:
                 sb.write('GenericCovariantImpl+Covariant');
                 break;
             }
             comma = ',';
           }
         }
       }
       Map<String, int>? namedParameters = _namedParameters;
       if (namedParameters != null) {
         for (String name in namedParameters.keys) {
           int covariance = namedParameters[name]!;
           if (covariance != 0) {
             sb.write(comma);
             sb.write('$name:');

             switch (covariance) {
               case GenericCovariantImpl:
                 sb.write('GenericCovariantImpl');
                 break;
               case Covariant:
                 sb.write('Covariant');
                 break;
               default:
                 sb.write('GenericCovariantImpl+Covariant');
                 break;
             }
             comma = ',';
           }
         }
       }
       List<bool>? typeParameters = _typeParameters;
       if (typeParameters != null) {
         sb.write(comma);
         sb.write('types:');
         comma = '';
         for (int index = 0; index < typeParameters.length; index++) {
           if (typeParameters[index]) {
             sb.write(comma);
             sb.write('$index');
             comma = ',';
           }
         }
       }
       sb.write(')');
     }
     return sb.toString();
   }
 }
	// 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 'dart:math';

	import 'package:kernel/ast.dart';

	/// Class that holds the covariant and generic-covariant-impl information for
	/// a member.
	// TODO(johnniwinther): Cache this in ClassMember.
	// TODO(johnniwinther): Maybe compact initial positional masks into a single
	// int.
	class Covariance {
	static const int GenericCovariantImpl = 1;
	static const int Covariant = 2;

	/// Returns the covariance mask for [parameter].
	static int covarianceFromParameter(VariableDeclaration parameter) =>
	(parameter.isCovariantByDeclaration ? Covariant : 0) \|
	(parameter.isCovariantByClass ? GenericCovariantImpl : 0);

	/// Returns the covariance mask for [field].
	static int covarianceFromField(Field field) =>
	(field.isCovariantByDeclaration ? Covariant : 0) \|
	(field.isCovariantByClass ? GenericCovariantImpl : 0);

	/// Applies the [covariance] mask to [parameter].
	static void covarianceToParameter(
	int covariance, VariableDeclaration parameter) {
	if ((covariance & Covariant) != 0) {
	parameter.isCovariantByDeclaration = true;
	}
	if ((covariance & GenericCovariantImpl) != 0) {
	parameter.isCovariantByClass = true;
	}
	}

	/// Applies the [covariance] mask to parameter.
	static void covarianceToField(int covariance, Field field) {
	if ((covariance & Covariant) != 0) {
	field.isCovariantByDeclaration = true;
	}
	if ((covariance & GenericCovariantImpl) != 0) {
	field.isCovariantByClass = true;
	}
	}

	/// The covariance mask for the positional parameters.
	///
	/// If no positional parameters have covariance, this is `null`.
	final List<int>? _positionalParameters;

	/// The covariance mask for the named parameters with name covariance.
	///
	/// If no named parameters have covariance, this is `null`.
	final Map<String, int>? _namedParameters;

	/// The generic-covariant-impl state for the type parameters.
	///
	/// If no type parameters are generic-covariant-impl, this is `null`.
	final List<bool>? _typeParameters;

	Covariance.internal(
	this._positionalParameters, this._namedParameters, this._typeParameters) {
	assert(_positionalParameters == null \|\|
	_positionalParameters.any((element) => element != 0));
	assert(_namedParameters == null \|\|
	_namedParameters.values.isNotEmpty &&
	_namedParameters.values.every((element) => element != 0));
	assert(
	_typeParameters == null \|\| _typeParameters.any((element) => element));
	}

	/// The empty covariance.
	///
	/// This is used for all members that do not use any covariance, regardless
	/// of parameter structure.
	const Covariance.empty()
	: _positionalParameters = null,
	_namedParameters = null,
	_typeParameters = null;

	/// Computes the covariance for the setter aspect of [field].
	///
	/// The getter aspect of a field never uses covariance.
	factory Covariance.fromField(Field field) {
	int covariance = covarianceFromField(field);
	if (covariance == 0) {
	return const Covariance.empty();
	}
	return new Covariance.internal(<int>[covariance], null, null);
	}

	/// Computes the covariance for the [setter].
	factory Covariance.fromSetter(Procedure setter) {
	int covariance =
	covarianceFromParameter(setter.function.positionalParameters.first);
	if (covariance == 0) {
	return const Covariance.empty();
	}
	return new Covariance.internal(<int>[covariance], null, null);
	}

	/// Computes the covariance for the [procedure].
	factory Covariance.fromMethod(Procedure procedure) {
	FunctionNode function = procedure.function;
	List<int>? positionalParameters;
	if (function.positionalParameters.isNotEmpty) {
	for (int index = 0;
	index < function.positionalParameters.length;
	index++) {
	int covariance =
	covarianceFromParameter(function.positionalParameters[index]);
	if (covariance != 0) {
	positionalParameters ??=
	new List<int>.filled(function.positionalParameters.length, 0);
	positionalParameters[index] = covariance;
	}
	}
	}
	Map<String, int>? namedParameters;
	if (function.namedParameters.isNotEmpty) {
	for (int index = 0; index < function.namedParameters.length; index++) {
	VariableDeclaration parameter = function.namedParameters[index];
	int covariance = covarianceFromParameter(parameter);
	if (covariance != 0) {
	namedParameters ??= {};
	namedParameters[parameter.name!] = covariance;
	}
	}
	}
	List<bool>? typeParameters;
	if (function.typeParameters.isNotEmpty) {
	for (int index = 0; index < function.typeParameters.length; index++) {
	if (function.typeParameters[index].isCovariantByClass) {
	typeParameters ??=
	new List<bool>.filled(function.typeParameters.length, false);
	typeParameters[index] = true;
	}
	}
	}
	if (positionalParameters == null &&
	namedParameters == null &&
	typeParameters == null) {
	return const Covariance.empty();
	}
	return new Covariance.internal(
	positionalParameters, namedParameters, typeParameters);
	}

	/// Computes the covariance for [member].
	///
	/// If [forSetter] is `true`, the covariance is computed for the setter
	/// aspect of [member]. Otherwise, the covariance for the getter/method aspect
	/// of [member] is computed.
	factory Covariance.fromMember(Member member, {required bool forSetter}) {
	if (member is Procedure) {
	if (member.kind == ProcedureKind.Getter) {
	return const Covariance.empty();
	} else if (member.kind == ProcedureKind.Setter) {
	return new Covariance.fromSetter(member);
	} else {
	return new Covariance.fromMethod(member);
	}
	} else if (member is Field) {
	if (forSetter) {
	return new Covariance.fromField(member);
	} else {
	return const Covariance.empty();
	}
	} else {
	throw new UnsupportedError(
	"Unexpected member $member (${member.runtimeType})");
	}
	}

	/// Returns `true` if this is the empty covariance.
	bool get isEmpty =>
	_positionalParameters == null &&
	_namedParameters == null &&
	_typeParameters == null;

	/// Returns the covariance mask for the [index]th positional parameter.
	int getPositionalVariance(int index) {
	List<int>? positionalParameters = _positionalParameters;
	return positionalParameters != null && index < positionalParameters.length
	? positionalParameters[index]
	: 0;
	}

	/// Returns the covariance mask for the named parameter with the [name].
	int getNamedVariance(String name) {
	Map<String, int>? namedParameters = _namedParameters;
	return namedParameters != null ? (namedParameters[name] ?? 0) : 0;
	}

	/// Returns `true` if the [index]th type parameter is generic-covariant-impl.
	bool isTypeParameterGenericCovariantImpl(int index) {
	List<bool>? typeParameters = _typeParameters;
	return typeParameters != null && index < typeParameters.length
	? typeParameters[index]
	: false;
	}

	/// Returns the merge of this covariance with [other] in which parameters are
	/// covariant if they are covariant in either this [Covariance] or [other].
	Covariance merge(Covariance other) {
	if (identical(this, other)) return this;
	List<int>? positionalParameters;
	if (_positionalParameters == null) {
	positionalParameters = other._positionalParameters;
	} else if (other._positionalParameters == null) {
	positionalParameters = _positionalParameters;
	} else {
	positionalParameters = new List<int>.filled(
	max(_positionalParameters.length, other._positionalParameters.length),
	0);
	for (int index = 0; index < positionalParameters.length; index++) {
	positionalParameters[index] =
	getPositionalVariance(index) \| other.getPositionalVariance(index);
	}
	}
	Map<String, int>? namedParameters;
	if (_namedParameters == null) {
	namedParameters = other._namedParameters;
	} else if (other._namedParameters == null) {
	namedParameters = _namedParameters;
	} else {
	namedParameters = {};
	Set<String> names = {
	..._namedParameters.keys,
	...other._namedParameters.keys
	};
	for (String name in names) {
	namedParameters[name] =
	getNamedVariance(name) \| other.getNamedVariance(name);
	}
	}
	List<bool>? typeParameters;
	if (_typeParameters == null) {
	typeParameters = other._typeParameters;
	} else if (other._typeParameters == null) {
	typeParameters = _typeParameters;
	} else {
	typeParameters = new List<bool>.filled(
	max(_typeParameters.length, other._typeParameters.length), false);
	for (int index = 0; index < typeParameters.length; index++) {
	typeParameters[index] = isTypeParameterGenericCovariantImpl(index) \|\|
	other.isTypeParameterGenericCovariantImpl(index);
	}
	}
	if (positionalParameters == null &&
	namedParameters == null &&
	typeParameters == null) {
	return const Covariance.empty();
	}
	return new Covariance.internal(
	positionalParameters, namedParameters, typeParameters);
	}

	/// Update [member] to have the covariant flags set with the covariance in
	/// this [Covariance].
	///
	/// No covariance bits are removed from [member] during this process.
	void applyCovariance(Member member) {
	if (isEmpty) return;
	if (member is Procedure) {
	FunctionNode function = member.function;
	List<int>? positionalParameters = _positionalParameters;
	if (positionalParameters != null) {
	for (int index = 0; index < positionalParameters.length; index++) {
	if (index < function.positionalParameters.length) {
	covarianceToParameter(positionalParameters[index],
	function.positionalParameters[index]);
	}
	}
	}
	if (_namedParameters != null) {
	for (VariableDeclaration parameter in function.namedParameters) {
	covarianceToParameter(getNamedVariance(parameter.name!), parameter);
	}
	}
	List<bool>? typeParameters = _typeParameters;
	if (typeParameters != null) {
	for (int index = 0; index < typeParameters.length; index++) {
	if (index < function.typeParameters.length) {
	if (typeParameters[index]) {
	function.typeParameters[index].isCovariantByClass = true;
	}
	}
	}
	}
	} else if (member is Field) {
	if (_positionalParameters != null) {
	covarianceToField(getPositionalVariance(0), member);
	}
	} else {
	throw new UnsupportedError(
	"Unexpected member $member (${member.runtimeType})");
	}
	}

	@override
	int get hashCode {
	int hash = 0;
	List<int>? positionalParameters = _positionalParameters;
	if (positionalParameters != null) {
	for (int covariance in positionalParameters) {
	hash += covariance.hashCode * 17;
	}
	}
	Map<String, int>? namedParameters = _namedParameters;
	if (namedParameters != null) {
	for (String name in namedParameters.keys) {
	hash += name.hashCode * 19 + namedParameters[name].hashCode * 23;
	}
	}
	List<bool>? typeParameters = _typeParameters;
	if (typeParameters != null) {
	for (bool covariance in typeParameters) {
	if (covariance) {
	hash += covariance.hashCode * 31;
	}
	}
	}
	return hash;
	}

	@override
	bool operator ==(Object other) {
	if (identical(this, other)) return true;
	if (other is Covariance) {
	if (_positionalParameters != other._positionalParameters) {
	if (_positionalParameters == null \|\|
	other._positionalParameters == null) {
	return false;
	}
	int positionalParameterCount = max(
	_positionalParameters.length, other._positionalParameters.length);
	for (int i = 0; i < positionalParameterCount; i++) {
	if (getPositionalVariance(i) != other.getPositionalVariance(i)) {
	return false;
	}
	}
	}
	if (_namedParameters != other._namedParameters) {
	if (_namedParameters == null \|\| other._namedParameters == null) {
	return false;
	}
	Set<String> names = {
	..._namedParameters.keys,
	...other._namedParameters.keys
	};
	for (String name in names) {
	if (getNamedVariance(name) != other.getNamedVariance(name)) {
	return false;
	}
	}
	}
	if (_typeParameters != other._typeParameters) {
	if (_typeParameters == null \|\| other._typeParameters == null) {
	return false;
	}
	int typeParameterCount =
	max(_typeParameters.length, other._typeParameters.length);
	for (int i = 0; i < typeParameterCount; i++) {
	if (isTypeParameterGenericCovariantImpl(i) !=
	other.isTypeParameterGenericCovariantImpl(i)) {
	return false;
	}
	}
	}
	return true;
	}
	return false;
	}

	@override
	String toString() {
	StringBuffer sb = new StringBuffer();
	if (isEmpty) {
	sb.write('Covariance.empty()');
	} else {
	sb.write('Covariance(');
	String comma = '';
	List<int>? positionalParameters = _positionalParameters;
	if (positionalParameters != null) {
	for (int index = 0; index < positionalParameters.length; index++) {
	if (positionalParameters[index] != 0) {
	sb.write(comma);
	sb.write('$index:');
	switch (positionalParameters[index]) {
	case GenericCovariantImpl:
	sb.write('GenericCovariantImpl');
	break;
	case Covariant:
	sb.write('Covariant');
	break;
	default:
	sb.write('GenericCovariantImpl+Covariant');
	break;
	}
	comma = ',';
	}
	}
	}
	Map<String, int>? namedParameters = _namedParameters;
	if (namedParameters != null) {
	for (String name in namedParameters.keys) {
	int covariance = namedParameters[name]!;
	if (covariance != 0) {
	sb.write(comma);
	sb.write('$name:');

	switch (covariance) {
	case GenericCovariantImpl:
	sb.write('GenericCovariantImpl');
	break;
	case Covariant:
	sb.write('Covariant');
	break;
	default:
	sb.write('GenericCovariantImpl+Covariant');
	break;
	}
	comma = ',';
	}
	}
	}
	List<bool>? typeParameters = _typeParameters;
	if (typeParameters != null) {
	sb.write(comma);
	sb.write('types:');
	comma = '';
	for (int index = 0; index < typeParameters.length; index++) {
	if (typeParameters[index]) {
	sb.write(comma);
	sb.write('$index');
	comma = ',';
	}
	}
	}
	sb.write(')');
	}
	return sb.toString();
	}
	}