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const BuiltList with Expando to cache hashCode #283

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const BuiltList with Expando to cache hashCode #283

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2 changes: 2 additions & 0 deletions lib/src/iterable/built_iterable.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -11,4 +11,6 @@ abstract class BuiltIterable<E> implements Iterable<E> {

/// Converts to a [BuiltSet].
BuiltSet<E> toBuiltSet();

const BuiltIterable();
}
12 changes: 7 additions & 5 deletions lib/src/list/built_list.dart
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Expand Up @@ -4,6 +4,8 @@

part of '../list.dart';

final _hashCodeExpando = Expando<int>();

/// The Built Collection [List].
///
/// It implements [Iterable] and the non-mutating part of the [List] interface.
Expand All @@ -15,7 +17,6 @@ part of '../list.dart';
/// for the general properties of Built Collections.
abstract class BuiltList<E> implements Iterable<E>, BuiltIterable<E> {
final List<E> _list;
int? _hashCode;

/// Instantiates with elements from an [Iterable].
factory BuiltList([Iterable iterable = const []]) {
Expand All @@ -26,6 +27,8 @@ abstract class BuiltList<E> implements Iterable<E>, BuiltIterable<E> {
}
}

const factory BuiltList.fromList([List<E> list]) = _BuiltList<E>.withSafeList;

/// Instantiates with elements from an [Iterable<E>].
///
/// `E` must not be `dynamic`.
Expand Down Expand Up @@ -62,8 +65,7 @@ abstract class BuiltList<E> implements Iterable<E>, BuiltIterable<E> {
/// the same order. Then, the `hashCode` is guaranteed to be the same.
@override
int get hashCode {
_hashCode ??= hashObjects(_list);
return _hashCode!;
return _hashCodeExpando[this] ??= hashObjects(_list);
}

/// Deep equality.
Expand Down Expand Up @@ -234,12 +236,12 @@ abstract class BuiltList<E> implements Iterable<E>, BuiltIterable<E> {

// Internal.

BuiltList._(this._list);
const BuiltList._(this._list);
}

/// Default implementation of the public [BuiltList] interface.
class _BuiltList<E> extends BuiltList<E> {
_BuiltList.withSafeList(List<E> list) : super._(list);
const _BuiltList.withSafeList([List<E> list = const []]) : super._(list);

_BuiltList.from([Iterable iterable = const []])
: super._(List<E>.from(iterable, growable: false)) {
Expand Down
6 changes: 3 additions & 3 deletions lib/src/list/list_builder.dart
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Expand Up @@ -13,7 +13,7 @@ part of '../list.dart';
/// for the general properties of Built Collections.
class ListBuilder<E> {
late List<E> _list;
_BuiltList<E>? _listOwner;
BuiltList<E>? _listOwner;

/// Instantiates with elements from an [Iterable].
factory ListBuilder([Iterable iterable = const []]) {
Expand All @@ -38,7 +38,7 @@ class ListBuilder<E> {

/// Replaces all elements with elements from an [Iterable].
void replace(Iterable iterable) {
if (iterable is _BuiltList<E>) {
if (iterable is BuiltList<E>) {
_setOwner(iterable);
} else {
_setSafeList(List<E>.from(iterable));
Expand Down Expand Up @@ -258,7 +258,7 @@ class ListBuilder<E> {

ListBuilder._uninitialized();

void _setOwner(_BuiltList<E> listOwner) {
void _setOwner(BuiltList<E> listOwner) {
_list = listOwner._list;
_listOwner = listOwner;
}
Expand Down