built_value/lib/built_value.dart - third_party/dart-pkg - Git at Google

 // Copyright (c) 2015, Google Inc. 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:meta/meta_meta.dart';

 /// Implement this for a Built Value.
 ///
 /// Then use built_value_generator.dart code generation functionality to
 /// provide the rest of the implementation.
 ///
 /// See https://github.com/google/built_value.dart/tree/master/example
 abstract class Built<V extends Built<V, B>, B extends Builder<V, B>> {
   /// Rebuilds the instance.
   ///
   /// The result is the same as this instance but with [updates] applied.
   /// [updates] is a function that takes a builder [B].
   ///
   /// The implementation of this method will be generated for you by the
   /// built_value generator.
   V rebuild(Function(B) updates);

   /// Converts the instance to a builder [B].
   ///
   /// The implementation of this method will be generated for you by the
   /// built_value generator.
   B toBuilder();
 }

 /// Every [Built] class has a corresponding [Builder] class.
 ///
 /// Usually you don't need to create one by hand; it will be generated
 /// for you.
 ///
 /// See <https://github.com/google/built_value.dart/tree/master/example>
 abstract class Builder<V extends Built<V, B>, B extends Builder<V, B>> {
   /// Replaces the value in the builder with a new one.
   ///
   /// The implementation of this method will be generated for you by the
   /// built_value generator.
   void replace(V value);

   /// Applies updates.
   ///
   /// [updates] is a function that takes a builder [B].
   void update(Function(B)? updates);

   /// Builds.
   ///
   /// The implementation of this method will be generated for you by the
   /// built_value generator.
   V build();
 }

 /// Optionally, annotate a Built Value with this to specify settings. This is
 /// only needed for advanced use.
 class BuiltValue {
   /// Whether the Built Value is instantiable. Defaults to `true`.
   ///
   /// A non-instantiable Built Value has no constructor or factory. No
   /// implementation will be generated. But, an abstract builder will be
   /// generated, or you may write one yourself.
   ///
   /// Other Built Values may choose to `implement` a non-instantiable Built
   /// Value, pulling in fields and methods from it. Their generated builders
   /// will automatically `implement` the corresponding builder, so you can
   /// access and modify the common inherited fields without knowing the
   /// concrete type.
   final bool instantiable;

   /// Whether to use nested builders. Defaults to `true`.
   ///
   /// If the builder class is fully generated, controls whether nested builders
   /// are used. This means builder fields are themselves builders if there is a
   /// builder available for each field type.
   ///
   /// If you write the builder class by hand, this has no effect; simply
   /// declare each field as the type you want, either the built type or the
   /// builder.
   final bool nestedBuilders;

   /// Whether to auto create nested builders. Defaults to `true`.
   ///
   /// When this is enabled, accessing a nested builder via a getter causes it
   /// to be instantiated if it's `null`. In most cases this is convenient, but
   /// if you are using builders for data processing then you might need to
   /// check for `null`. If so you should set this to `false`.
   final bool autoCreateNestedBuilders;

   /// Whether builders should implement `operator==` and `hashCode`, making
   /// them comparable.
   ///
   /// May only be used with `nestedBuilders: false` and if the builder class
   /// is fully generated.
   final bool comparableBuilders;

   /// Whether to generate an `onSet` field in the builder.
   ///
   /// Defaults to `false`.
   ///
   /// If generated the `onSet` field will have type `void Function()`, and will
   /// be called after any setter is called. Assign your own function to
   /// `onSet` to respond to changes to the builder.
   final bool generateBuilderOnSetField;

   /// The wire name when the class is serialized. Defaults to `null` which
   /// indicates that the name is to be taken from the literal class name.
   final String? wireName;

   /// The default for [BuiltValueField.compare]. Set to `false` if you want to
   /// ignore most fields when comparing, then mark the ones you do want to
   /// compare on with `@BuiltValueField(compare: true)`.
   final bool defaultCompare;

   /// The default for [BuiltValueField.serialize]. Set to `false` if you want
   /// to ignore most fields when serializing, then mark the ones you do want
   /// to serialize with `@BuiltValueField(serialize: true)`.
   final bool defaultSerialize;

   const BuiltValue(
       {this.instantiable = true,
       this.nestedBuilders = true,
       this.autoCreateNestedBuilders = true,
       this.comparableBuilders = false,
       this.generateBuilderOnSetField = false,
       this.wireName,
       this.defaultCompare = true,
       this.defaultSerialize = true});
 }

 /// Nullable annotation for Built Value fields.
 ///
 /// Fields marked with this annotation are allowed to be null.
 const String nullable = 'nullable';

 /// Optionally, annotate a Built Value field with this to specify settings.
 /// This is only needed for advanced use.
 @Target({TargetKind.getter})
 class BuiltValueField {
   /// Whether the field is compared and hashed. Defaults to `null` which means
   /// [BuiltValue.defaultCompare] is used.
   ///
   /// Set to `false` to ignore the field when calculating `hashCode` and when
   /// comparing with `operator==`.
   final bool? compare;

   /// Whether the field is serialized. Defaults to `null` which means
   /// [BuiltValue.defaultSerialize] is used.
   ///
   /// If a field is not serialized, it must either be `@nullable` or specify a
   /// default for deserialization to succeed.
   final bool? serialize;

   /// The wire name when the field is serialized. Defaults to `null` which
   /// indicates the name is to be taken from the literal field name.
   final String? wireName;

   /// Whether the field overrides the `nestedBuilders` setting from the class. Defaults to `null` which
   /// indicates the setting is to be taken from the `nestedBuilders` setting on the class.
   final bool? nestedBuilder;

   /// Whether the field overrides the `autoCreateNestedBuilders` setting from the class. Defaults to `null` which
   /// indicates the setting is to be taken from the `autoCreateNestedBuilders` setting on the class.
   final bool? autoCreateNestedBuilder;

   const BuiltValueField(
       {this.compare,
       this.serialize,
       this.wireName,
       this.nestedBuilder,
       this.autoCreateNestedBuilder});
 }

 /// Optionally, annotate a Built Value `Serializer` getters with this to
 /// specify settings. This is only needed for advanced use.
 @Target({TargetKind.getter})
 class BuiltValueSerializer {
   /// Set this to `true` to stop Built Value from generating a serializer for
   /// you. The getter may then return any compatible `Serializer`. Defaults
   /// to `false`.
   final bool custom;

   /// Whether the generated serializer should output `null`s.
   ///
   /// By default this is `false` and nulls are omitted from the output.

   final bool serializeNulls;

   const BuiltValueSerializer(
       {this.custom = false, this.serializeNulls = false});
 }

 /// Memoized annotation for Built Value getters.
 ///
 /// Getters marked with this annotation are memoized: the result is calculated
 /// once on first access and stored in the instance.
 const String memoized = 'memoized';

 /// Optionally, annotate an `EnumClass` with this to specify settings. This
 /// is only needed for advanced use.
 @Target({TargetKind.classType})
 class BuiltValueEnum {
   /// The wire name when the enum is serialized. Defaults to `null` which
   /// indicates that the name is to be taken from the literal class name.
   final String? wireName;

   const BuiltValueEnum({this.wireName});
 }

 /// Optionally, annotate an `EnumClass` constant with this to specify settings.
 /// This is only needed for advanced use.
 @Target({TargetKind.field})
 class BuiltValueEnumConst {
   /// The wire name when the constant is serialized. Defaults to `null` which
   /// indicates the name is to be taken from the literal field name.
   ///
   /// Or, set [wireNumber] to serialize to an `int`. Only one of the two may be
   /// used.
   final String? wireName;

   /// The wire name when the constant is serialized. Defaults to `null` which
   /// indicates the name is to be taken from the literal field name.
   ///
   /// Or, set [wireName] to serialize to a `String`. Only one of the two may
   /// be used.
   final int? wireNumber;

   /// Marks a value that is used as a fallback when an unrecognized value
   /// is encountered.
   ///
   /// Defaults to `false`. At most one fallback is allowed per `EnumClass`.
   ///
   /// Applies to the `valueOf` method and to deserialization; both will use
   /// the fallback, if available, rather than throwing an exception.
   final bool fallback;

   const BuiltValueEnumConst(
       {this.wireName, this.wireNumber, this.fallback = false});
 }

 /// Optionally, annotate methods with this to cause them to be called by
 /// generated code.
 @Target({TargetKind.method})
 class BuiltValueHook {
   /// Marks a static method that will be called when the builder for the
   /// enclosing value type is initialized.
   ///
   /// The method must accept a builder of the enclosing value type.
   ///
   /// This example uses it to set a default value:
   ///
   /// ```
   /// @BuiltValueHook(initializeBuilder: true)
   /// static void _initializeBuilder(MyClassBuilder b) =>
   ///    b..name = 'defaultName';
   ///
   /// Defaults to `false`.
   /// ```
   final bool initializeBuilder;

   /// Marks a static method that will be called immediately before the builder
   /// for the enclosing value type is built.
   ///
   /// The method must accept a builder of the enclosing value type.
   ///
   /// This example uses it to make `items` sorted:
   ///
   /// ```
   /// @BuiltValueHook(initializeBuilder: true)
   /// static void _finalizeBuilder(MyClassBuilder b) =>
   ///    b..items.sort();
   ///
   /// Defaults to `false`.
   /// ```
   final bool finalizeBuilder;

   const BuiltValueHook(
       {this.initializeBuilder = false, this.finalizeBuilder = false});
 }

 /// Enum Class base class.
 ///
 /// Extend this class then use the built_value.dart code generation
 /// functionality to provide the rest of the implementation.
 ///
 /// See https://github.com/google/built_value.dart/tree/master/example
 class EnumClass {
   final String name;

   const EnumClass(this.name);

   @override
   String toString() => name;
 }

 /// For use by generated code in calculating hash codes. Do not use directly.
 int $jc(int hash, int value) {
   // Jenkins hash "combine".
   hash = 0x1fffffff & (hash + value);
   hash = 0x1fffffff & (hash + ((0x0007ffff & hash) << 10));
   return hash ^ (hash >> 6);
 }

 /// For use by generated code in calculating hash codes. Do not use directly.
 int $jf(int hash) {
   // Jenkins hash "finish".
   hash = 0x1fffffff & (hash + ((0x03ffffff & hash) << 3));
   hash = hash ^ (hash >> 11);
   return 0x1fffffff & (hash + ((0x00003fff & hash) << 15));
 }

 /// Function that returns a [BuiltValueToStringHelper].
 typedef BuiltValueToStringHelperProvider = BuiltValueToStringHelper Function(
     String className);

 /// Function used by generated code to get a [BuiltValueToStringHelper].
 /// Set this to change built_value class toString() output. Built-in examples
 /// are [IndentingBuiltValueToStringHelper], which is the default, and
 /// [FlatBuiltValueToStringHelper].
 BuiltValueToStringHelperProvider newBuiltValueToStringHelper =
     (String className) => IndentingBuiltValueToStringHelper(className);

 /// Interface for built_value toString() output helpers.
 ///
 /// Note: this is an experimental feature. API may change without a major
 /// version increase.
 abstract class BuiltValueToStringHelper {
   /// Add a field and its value.
   void add(String field, Object? value);

   /// Returns to completed toString(). The helper may not be used after this
   /// method is called.
   @override
   String toString();
 }

 /// A [BuiltValueToStringHelper] that produces multi-line indented output.
 class IndentingBuiltValueToStringHelper implements BuiltValueToStringHelper {
   StringBuffer? _result = StringBuffer();

   IndentingBuiltValueToStringHelper(String className) {
     _result!..write(className)..write(' {\n');
     _indentingBuiltValueToStringHelperIndent += 2;
   }

   @override
   void add(String field, Object? value) {
     if (value != null) {
       _result!
         ..write(' ' * _indentingBuiltValueToStringHelperIndent)
         ..write(field)
         ..write('=')
         ..write(value)
         ..write(',\n');
     }
   }

   @override
   String toString() {
     _indentingBuiltValueToStringHelperIndent -= 2;
     _result!..write(' ' * _indentingBuiltValueToStringHelperIndent)..write('}');
     var stringResult = _result.toString();
     _result = null;
     return stringResult;
   }
 }

 int _indentingBuiltValueToStringHelperIndent = 0;

 /// A [BuiltValueToStringHelper] that produces single line output.
 class FlatBuiltValueToStringHelper implements BuiltValueToStringHelper {
   StringBuffer? _result = StringBuffer();
   bool _previousField = false;

   FlatBuiltValueToStringHelper(String className) {
     _result!..write(className)..write(' {');
   }

   @override
   void add(String field, Object? value) {
     if (value != null) {
       if (_previousField) _result!.write(',');
       _result!..write(field)..write('=')..write(value);
       _previousField = true;
     }
   }

   @override
   String toString() {
     _result!.write('}');
     var stringResult = _result.toString();
     _result = null;
     return stringResult;
   }
 }

 /// [Error] indicating that a built_value class constructor was called with
 /// a `null` value for a field not marked `@nullable`.
 class BuiltValueNullFieldError extends Error {
   final String type;
   final String field;

   BuiltValueNullFieldError(this.type, this.field);

   /// Throws a [BuiltValueNullFieldError] if [value] is `null`.
   static T checkNotNull<T>(T? value, String type, String field) {
     if (value == null) {
       throw BuiltValueNullFieldError(type, field);
     }
     return value;
   }

   @override
   String toString() =>
       'Tried to construct class "$type" with null field "$field". '
       'This is forbidden; to allow it, mark "$field" with @nullable.';
 }

 /// [Error] indicating that a built_value class constructor was called with
 /// a missing or `dynamic` type parameter.
 class BuiltValueMissingGenericsError extends Error {
   final String type;
   final String parameter;

   BuiltValueMissingGenericsError(this.type, this.parameter);

   @override
   String toString() =>
       'Tried to construct class "$type" with missing or dynamic '
       'type argument "$parameter". All type arguments must be specified.';
 }

 /// [Error] indicating that a built_value `build` method failed because a
 /// nested field builder failed.
 class BuiltValueNestedFieldError extends Error {
   final String type;
   final String field;
   final String error;

   BuiltValueNestedFieldError(this.type, this.field, this.error);

   @override
   String toString() =>
       'Tried to build class "$type" but nested builder for field "$field" '
       'threw: $error';
 }
	// Copyright (c) 2015, Google Inc. 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:meta/meta_meta.dart';

	/// Implement this for a Built Value.
	///
	/// Then use built_value_generator.dart code generation functionality to
	/// provide the rest of the implementation.
	///
	/// See https://github.com/google/built_value.dart/tree/master/example
	abstract class Built<V extends Built<V, B>, B extends Builder<V, B>> {
	/// Rebuilds the instance.
	///
	/// The result is the same as this instance but with [updates] applied.
	/// [updates] is a function that takes a builder [B].
	///
	/// The implementation of this method will be generated for you by the
	/// built_value generator.
	V rebuild(Function(B) updates);

	/// Converts the instance to a builder [B].
	///
	/// The implementation of this method will be generated for you by the
	/// built_value generator.
	B toBuilder();
	}

	/// Every [Built] class has a corresponding [Builder] class.
	///
	/// Usually you don't need to create one by hand; it will be generated
	/// for you.
	///
	/// See <https://github.com/google/built_value.dart/tree/master/example>
	abstract class Builder<V extends Built<V, B>, B extends Builder<V, B>> {
	/// Replaces the value in the builder with a new one.
	///
	/// The implementation of this method will be generated for you by the
	/// built_value generator.
	void replace(V value);

	/// Applies updates.
	///
	/// [updates] is a function that takes a builder [B].
	void update(Function(B)? updates);

	/// Builds.
	///
	/// The implementation of this method will be generated for you by the
	/// built_value generator.
	V build();
	}

	/// Optionally, annotate a Built Value with this to specify settings. This is
	/// only needed for advanced use.
	class BuiltValue {
	/// Whether the Built Value is instantiable. Defaults to `true`.
	///
	/// A non-instantiable Built Value has no constructor or factory. No
	/// implementation will be generated. But, an abstract builder will be
	/// generated, or you may write one yourself.
	///
	/// Other Built Values may choose to `implement` a non-instantiable Built
	/// Value, pulling in fields and methods from it. Their generated builders
	/// will automatically `implement` the corresponding builder, so you can
	/// access and modify the common inherited fields without knowing the
	/// concrete type.
	final bool instantiable;

	/// Whether to use nested builders. Defaults to `true`.
	///
	/// If the builder class is fully generated, controls whether nested builders
	/// are used. This means builder fields are themselves builders if there is a
	/// builder available for each field type.
	///
	/// If you write the builder class by hand, this has no effect; simply
	/// declare each field as the type you want, either the built type or the
	/// builder.
	final bool nestedBuilders;

	/// Whether to auto create nested builders. Defaults to `true`.
	///
	/// When this is enabled, accessing a nested builder via a getter causes it
	/// to be instantiated if it's `null`. In most cases this is convenient, but
	/// if you are using builders for data processing then you might need to
	/// check for `null`. If so you should set this to `false`.
	final bool autoCreateNestedBuilders;

	/// Whether builders should implement `operator==` and `hashCode`, making
	/// them comparable.
	///
	/// May only be used with `nestedBuilders: false` and if the builder class
	/// is fully generated.
	final bool comparableBuilders;

	/// Whether to generate an `onSet` field in the builder.
	///
	/// Defaults to `false`.
	///
	/// If generated the `onSet` field will have type `void Function()`, and will
	/// be called after any setter is called. Assign your own function to
	/// `onSet` to respond to changes to the builder.
	final bool generateBuilderOnSetField;

	/// The wire name when the class is serialized. Defaults to `null` which
	/// indicates that the name is to be taken from the literal class name.
	final String? wireName;

	/// The default for [BuiltValueField.compare]. Set to `false` if you want to
	/// ignore most fields when comparing, then mark the ones you do want to
	/// compare on with `@BuiltValueField(compare: true)`.
	final bool defaultCompare;

	/// The default for [BuiltValueField.serialize]. Set to `false` if you want
	/// to ignore most fields when serializing, then mark the ones you do want
	/// to serialize with `@BuiltValueField(serialize: true)`.
	final bool defaultSerialize;

	const BuiltValue(
	{this.instantiable = true,
	this.nestedBuilders = true,
	this.autoCreateNestedBuilders = true,
	this.comparableBuilders = false,
	this.generateBuilderOnSetField = false,
	this.wireName,
	this.defaultCompare = true,
	this.defaultSerialize = true});
	}

	/// Nullable annotation for Built Value fields.
	///
	/// Fields marked with this annotation are allowed to be null.
	const String nullable = 'nullable';

	/// Optionally, annotate a Built Value field with this to specify settings.
	/// This is only needed for advanced use.
	@Target({TargetKind.getter})
	class BuiltValueField {
	/// Whether the field is compared and hashed. Defaults to `null` which means
	/// [BuiltValue.defaultCompare] is used.
	///
	/// Set to `false` to ignore the field when calculating `hashCode` and when
	/// comparing with `operator==`.
	final bool? compare;

	/// Whether the field is serialized. Defaults to `null` which means
	/// [BuiltValue.defaultSerialize] is used.
	///
	/// If a field is not serialized, it must either be `@nullable` or specify a
	/// default for deserialization to succeed.
	final bool? serialize;

	/// The wire name when the field is serialized. Defaults to `null` which
	/// indicates the name is to be taken from the literal field name.
	final String? wireName;

	/// Whether the field overrides the `nestedBuilders` setting from the class. Defaults to `null` which
	/// indicates the setting is to be taken from the `nestedBuilders` setting on the class.
	final bool? nestedBuilder;

	/// Whether the field overrides the `autoCreateNestedBuilders` setting from the class. Defaults to `null` which
	/// indicates the setting is to be taken from the `autoCreateNestedBuilders` setting on the class.
	final bool? autoCreateNestedBuilder;

	const BuiltValueField(
	{this.compare,
	this.serialize,
	this.wireName,
	this.nestedBuilder,
	this.autoCreateNestedBuilder});
	}

	/// Optionally, annotate a Built Value `Serializer` getters with this to
	/// specify settings. This is only needed for advanced use.
	@Target({TargetKind.getter})
	class BuiltValueSerializer {
	/// Set this to `true` to stop Built Value from generating a serializer for
	/// you. The getter may then return any compatible `Serializer`. Defaults
	/// to `false`.
	final bool custom;

	/// Whether the generated serializer should output `null`s.
	///
	/// By default this is `false` and nulls are omitted from the output.

	final bool serializeNulls;

	const BuiltValueSerializer(
	{this.custom = false, this.serializeNulls = false});
	}

	/// Memoized annotation for Built Value getters.
	///
	/// Getters marked with this annotation are memoized: the result is calculated
	/// once on first access and stored in the instance.
	const String memoized = 'memoized';

	/// Optionally, annotate an `EnumClass` with this to specify settings. This
	/// is only needed for advanced use.
	@Target({TargetKind.classType})
	class BuiltValueEnum {
	/// The wire name when the enum is serialized. Defaults to `null` which
	/// indicates that the name is to be taken from the literal class name.
	final String? wireName;

	const BuiltValueEnum({this.wireName});
	}

	/// Optionally, annotate an `EnumClass` constant with this to specify settings.
	/// This is only needed for advanced use.
	@Target({TargetKind.field})
	class BuiltValueEnumConst {
	/// The wire name when the constant is serialized. Defaults to `null` which
	/// indicates the name is to be taken from the literal field name.
	///
	/// Or, set [wireNumber] to serialize to an `int`. Only one of the two may be
	/// used.
	final String? wireName;

	/// The wire name when the constant is serialized. Defaults to `null` which
	/// indicates the name is to be taken from the literal field name.
	///
	/// Or, set [wireName] to serialize to a `String`. Only one of the two may
	/// be used.
	final int? wireNumber;

	/// Marks a value that is used as a fallback when an unrecognized value
	/// is encountered.
	///
	/// Defaults to `false`. At most one fallback is allowed per `EnumClass`.
	///
	/// Applies to the `valueOf` method and to deserialization; both will use
	/// the fallback, if available, rather than throwing an exception.
	final bool fallback;

	const BuiltValueEnumConst(
	{this.wireName, this.wireNumber, this.fallback = false});
	}

	/// Optionally, annotate methods with this to cause them to be called by
	/// generated code.
	@Target({TargetKind.method})
	class BuiltValueHook {
	/// Marks a static method that will be called when the builder for the
	/// enclosing value type is initialized.
	///
	/// The method must accept a builder of the enclosing value type.
	///
	/// This example uses it to set a default value:
	///
	/// ```
	/// @BuiltValueHook(initializeBuilder: true)
	/// static void _initializeBuilder(MyClassBuilder b) =>
	/// b..name = 'defaultName';
	///
	/// Defaults to `false`.
	/// ```
	final bool initializeBuilder;

	/// Marks a static method that will be called immediately before the builder
	/// for the enclosing value type is built.
	///
	/// The method must accept a builder of the enclosing value type.
	///
	/// This example uses it to make `items` sorted:
	///
	/// ```
	/// @BuiltValueHook(initializeBuilder: true)
	/// static void _finalizeBuilder(MyClassBuilder b) =>
	/// b..items.sort();
	///
	/// Defaults to `false`.
	/// ```
	final bool finalizeBuilder;

	const BuiltValueHook(
	{this.initializeBuilder = false, this.finalizeBuilder = false});
	}

	/// Enum Class base class.
	///
	/// Extend this class then use the built_value.dart code generation
	/// functionality to provide the rest of the implementation.
	///
	/// See https://github.com/google/built_value.dart/tree/master/example
	class EnumClass {
	final String name;

	const EnumClass(this.name);

	@override
	String toString() => name;
	}

	/// For use by generated code in calculating hash codes. Do not use directly.
	int $jc(int hash, int value) {
	// Jenkins hash "combine".
	hash = 0x1fffffff & (hash + value);
	hash = 0x1fffffff & (hash + ((0x0007ffff & hash) << 10));
	return hash ^ (hash >> 6);
	}

	/// For use by generated code in calculating hash codes. Do not use directly.
	int $jf(int hash) {
	// Jenkins hash "finish".
	hash = 0x1fffffff & (hash + ((0x03ffffff & hash) << 3));
	hash = hash ^ (hash >> 11);
	return 0x1fffffff & (hash + ((0x00003fff & hash) << 15));
	}

	/// Function that returns a [BuiltValueToStringHelper].
	typedef BuiltValueToStringHelperProvider = BuiltValueToStringHelper Function(
	String className);

	/// Function used by generated code to get a [BuiltValueToStringHelper].
	/// Set this to change built_value class toString() output. Built-in examples
	/// are [IndentingBuiltValueToStringHelper], which is the default, and
	/// [FlatBuiltValueToStringHelper].
	BuiltValueToStringHelperProvider newBuiltValueToStringHelper =
	(String className) => IndentingBuiltValueToStringHelper(className);

	/// Interface for built_value toString() output helpers.
	///
	/// Note: this is an experimental feature. API may change without a major
	/// version increase.
	abstract class BuiltValueToStringHelper {
	/// Add a field and its value.
	void add(String field, Object? value);

	/// Returns to completed toString(). The helper may not be used after this
	/// method is called.
	@override
	String toString();
	}

	/// A [BuiltValueToStringHelper] that produces multi-line indented output.
	class IndentingBuiltValueToStringHelper implements BuiltValueToStringHelper {
	StringBuffer? _result = StringBuffer();

	IndentingBuiltValueToStringHelper(String className) {
	_result!..write(className)..write(' {\n');
	_indentingBuiltValueToStringHelperIndent += 2;
	}

	@override
	void add(String field, Object? value) {
	if (value != null) {
	_result!
	..write(' ' * _indentingBuiltValueToStringHelperIndent)
	..write(field)
	..write('=')
	..write(value)
	..write(',\n');
	}
	}

	@override
	String toString() {
	_indentingBuiltValueToStringHelperIndent -= 2;
	_result!..write(' ' * _indentingBuiltValueToStringHelperIndent)..write('}');
	var stringResult = _result.toString();
	_result = null;
	return stringResult;
	}
	}

	int _indentingBuiltValueToStringHelperIndent = 0;

	/// A [BuiltValueToStringHelper] that produces single line output.
	class FlatBuiltValueToStringHelper implements BuiltValueToStringHelper {
	StringBuffer? _result = StringBuffer();
	bool _previousField = false;

	FlatBuiltValueToStringHelper(String className) {
	_result!..write(className)..write(' {');
	}

	@override
	void add(String field, Object? value) {
	if (value != null) {
	if (_previousField) _result!.write(',');
	_result!..write(field)..write('=')..write(value);
	_previousField = true;
	}
	}

	@override
	String toString() {
	_result!.write('}');
	var stringResult = _result.toString();
	_result = null;
	return stringResult;
	}
	}

	/// [Error] indicating that a built_value class constructor was called with
	/// a `null` value for a field not marked `@nullable`.
	class BuiltValueNullFieldError extends Error {
	final String type;
	final String field;

	BuiltValueNullFieldError(this.type, this.field);

	/// Throws a [BuiltValueNullFieldError] if [value] is `null`.
	static T checkNotNull<T>(T? value, String type, String field) {
	if (value == null) {
	throw BuiltValueNullFieldError(type, field);
	}
	return value;
	}

	@override
	String toString() =>
	'Tried to construct class "$type" with null field "$field". '
	'This is forbidden; to allow it, mark "$field" with @nullable.';
	}

	/// [Error] indicating that a built_value class constructor was called with
	/// a missing or `dynamic` type parameter.
	class BuiltValueMissingGenericsError extends Error {
	final String type;
	final String parameter;

	BuiltValueMissingGenericsError(this.type, this.parameter);

	@override
	String toString() =>
	'Tried to construct class "$type" with missing or dynamic '
	'type argument "$parameter". All type arguments must be specified.';
	}

	/// [Error] indicating that a built_value `build` method failed because a
	/// nested field builder failed.
	class BuiltValueNestedFieldError extends Error {
	final String type;
	final String field;
	final String error;

	BuiltValueNestedFieldError(this.type, this.field, this.error);

	@override
	String toString() =>
	'Tried to build class "$type" but nested builder for field "$field" '
	'threw: $error';
	}