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pkg/dev_compiler/tool/input_sdk/lib/collection/linked_hash_map.dart

-// Copyright (c) 2013, 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.
-
-part of dart.collection;
-
-/**
- * A hash-table based implementation of [Map].
- *
- * The insertion order of keys is remembered,
- * and keys are iterated in the order they were inserted into the map.
- * Values are iterated in their corresponding key's order.
- * Changing a key's value, when the key is already in the map,
- * does not change the iteration order,
- * but removing the key and adding it again
- * will make it be last in the iteration order.
- *
- * The keys of a `LinkedHashMap` must have consistent [Object.operator==]
- * and [Object.hashCode] implementations. This means that the `==` operator
- * must define a stable equivalence relation on the keys (reflexive,
- * symmetric, transitive, and consistent over time), and that `hashCode`
- * must be the same for objects that are considered equal by `==`.
- *
- * The map allows `null` as a key.
- */
-abstract class LinkedHashMap<K, V> implements HashMap<K, V> {
-  /**
-   * Creates an insertion-ordered hash-table based [Map].
-   *
-   * If [equals] is provided, it is used to compare the keys in the table with
-   * new keys. If [equals] is omitted, the key's own [Object.operator==] is used
-   * instead.
-   *
-   * Similar, if [hashCode] is provided, it is used to produce a hash value
-   * for keys in order to place them in the hash table. If it is omitted, the
-   * key's own [Object.hashCode] is used.
-   *
-   * If using methods like [operator[]], [remove] and [containsKey] together
-   * with a custom equality and hashcode, an extra `isValidKey` function
-   * can be supplied. This function is called before calling [equals] or
-   * [hashCode] with an argument that may not be a [K] instance, and if the
-   * call returns false, the key is assumed to not be in the set.
-   * The [isValidKey] function defaults to just testing if the object is a
-   * [K] instance.
-   *
-   * Example:
-   *
-   *     new LinkedHashMap<int,int>(equals: (int a, int b) => (b - a) % 5 == 0,
-   *                                hashCode: (int e) => e % 5)
-   *
-   * This example map does not need an `isValidKey` function to be passed.
-   * The default function accepts only `int` values, which can safely be
-   * passed to both the `equals` and `hashCode` functions.
-   *
-   * If neither `equals`, `hashCode`, nor `isValidKey` is provided,
-   * the default `isValidKey` instead accepts all keys.
-   * The default equality and hashcode operations are assumed to work on all
-   * objects.
-   *
-   * Likewise, if `equals` is [identical], `hashCode` is [identityHashCode]
-   * and `isValidKey` is omitted, the resulting map is identity based,
-   * and the `isValidKey` defaults to accepting all keys.
-   * Such a map can be created directly using [LinkedHashMap.identity].
-   *
-   * The used `equals` and `hashCode` method should always be consistent,
-   * so that if `equals(a, b)` then `hashCode(a) == hashCode(b)`. The hash
-   * of an object, or what it compares equal to, should not change while the
-   * object is in the table. If it does change, the result is unpredictable.
-   *
-   * If you supply one of [equals] and [hashCode],
-   * you should generally also to supply the other.
-   */
-  external factory LinkedHashMap({bool equals(K key1, K key2),
-                                  int hashCode(K key),
-                                  bool isValidKey(Object potentialKey)});
-
-  /**
-   * Creates an insertion-ordered identity-based map.
-   *
-   * Effectively a shorthand for:
-   *
-   *     new LinkedHashMap(equals: identical,
-   *                       hashCode: identityHashCode)
-   */
-  external factory LinkedHashMap.identity();
-
-  /**
-   * Creates a [LinkedHashMap] that contains all key value pairs of [other].
-   */
-  factory LinkedHashMap.from(Map other) {
-    LinkedHashMap<K, V> result = new LinkedHashMap<K, V>();
-    other.forEach((k, v) { result[k as Object/*=K*/] = v as Object/*=V*/; });
-    return result;
-  }
-
-  /**
-   * Creates a [LinkedHashMap] where the keys and values are computed from the
-   * [iterable].
-   *
-   * For each element of the [iterable] this constructor computes a key/value
-   * pair, by applying [key] and [value] respectively.
-   *
-   * The keys of the key/value pairs do not need to be unique. The last
-   * occurrence of a key will simply overwrite any previous value.
-   *
-   * If no values are specified for [key] and [value] the default is the
-   * identity function.
-   */
-  factory LinkedHashMap.fromIterable(Iterable iterable,
-      {K key(element), V value(element)}) {
-    LinkedHashMap<K, V> map = new LinkedHashMap<K, V>();
-    Maps._fillMapWithMappedIterable(map, iterable, key, value);
-    return map;
-  }
-
-  /**
-   * Creates a [LinkedHashMap] associating the given [keys] to [values].
-   *
-   * This constructor iterates over [keys] and [values] and maps each element of
-   * [keys] to the corresponding element of [values].
-   *
-   * If [keys] contains the same object multiple times, the last occurrence
-   * overwrites the previous value.
-   *
-   * It is an error if the two [Iterable]s don't have the same length.
-   */
-  factory LinkedHashMap.fromIterables(Iterable<K> keys, Iterable<V> values) {
-    LinkedHashMap<K, V> map = new LinkedHashMap<K, V>();
-    Maps._fillMapWithIterables(map, keys, values);
-    return map;
-  }
-}