Make EfficientLength extend Iterable.

This should help least-upper-bound computations to not think of EfficientLength
as completely separate from Iterable even though they are always used together.

It doesn't solve all problems with the least-upper-bound computation,
but at least some of the more often occuring ones.

R=floitsch@google.com

Review URL: https://codereview.chromium.org/2467113003 .

Committed: b08fb1373f

runtime/lib/array_patch.dart

@@ -33,7 +33,7 @@ const _GROWABLE_ARRAY_MARKER = const _GrowableArrayMarker();
   }
 
   @patch factory List.from(Iterable elements, { bool growable: true }) {
-    if (elements is EfficientLength) {
+    if (elements is EfficientLengthIterable) {
       int length = elements.length;
       var list = growable ? new _GrowableList<E>(length) : new _List<E>(length);
       if (length > 0) {  // Avoid creating iterator unless necessary.

runtime/lib/collection_patch.dart

@@ -435,8 +435,7 @@ class _HashMapEntry {
   _HashMapEntry(this.key, this.value, this.hashCode, this.next);
 }
 
-abstract class _HashMapIterable<E> extends IterableBase<E>
-                                   implements EfficientLength {
+abstract class _HashMapIterable<E> extends EfficientLengthIterable<E> {
   final HashMap _map;
   _HashMapIterable(this._map);
   int get length => _map.length;
@@ -838,8 +837,7 @@ class _LinkedHashMapEntry extends _HashMapEntry {
   }
 }
 
-class _LinkedHashMapKeyIterable<K> extends IterableBase<K>
-                                   implements EfficientLength {
+class _LinkedHashMapKeyIterable<K> extends EfficientLengthIterable<K> {
   LinkedHashMap<K, dynamic> _map;
   _LinkedHashMapKeyIterable(this._map);
   Iterator<K> get iterator => new _LinkedHashMapKeyIterator<K>(_map);
@@ -850,8 +848,7 @@ class _LinkedHashMapKeyIterable<K> extends IterableBase<K>
   Set<K> toSet() => _map._newKeySet()..addAll(this);
 }
 
-class _LinkedHashMapValueIterable<V> extends IterableBase<V>
-                                     implements EfficientLength {
+class _LinkedHashMapValueIterable<V> extends EfficientLengthIterable<V> {
   LinkedHashMap<dynamic, V> _map;
   _LinkedHashMapValueIterable(this._map);
   Iterator<V> get iterator => new _LinkedHashMapValueIterator<V>(_map);

runtime/lib/growable_array.dart

@@ -174,7 +174,7 @@ class _GrowableList<T> extends ListBase<T> {
         (cid == ClassID.cidArray) ||
         (cid == ClassID.cidGrowableObjectArray) ||
         (cid == ClassID.cidImmutableArray);
-    if (isVMList || (iterable is EfficientLength)) {
+    if (isVMList || (iterable is EfficientLengthIterable)) {
       var cap = _capacity;
       // Pregrow if we know iterable.length.
       var iterLen = iterable.length;

runtime/lib/immutable_map.dart

@@ -85,8 +85,7 @@ class ImmutableMap<K, V> implements Map<K, V> {
   }
 }
 
-class _ImmutableMapKeyIterable<E> extends IterableBase<E>
-                                  implements EfficientLength {
+class _ImmutableMapKeyIterable<E> extends EfficientLengthIterable<E> {
   final ImmutableMap _map;
   _ImmutableMapKeyIterable(this._map);
 
@@ -97,8 +96,7 @@ class _ImmutableMapKeyIterable<E> extends IterableBase<E>
   int get length => _map.length;
 }
 
-class _ImmutableMapValueIterable<E> extends IterableBase<E>
-                                    implements EfficientLength {
+class _ImmutableMapValueIterable<E> extends EfficientLengthIterable<E> {
   final ImmutableMap _map;
   _ImmutableMapValueIterable(this._map);
 

runtime/lib/string_patch.dart

@@ -155,7 +155,7 @@ abstract class _StringBase {
   static String _createStringFromIterable(Iterable<int> charCodes,
                                           int start, int end) {
     // Treat charCodes as Iterable.
-    if (charCodes is EfficientLength) {
+    if (charCodes is EfficientLengthIterable) {
       int length = charCodes.length;
       end = RangeError.checkValidRange(start, end, length);
       List charCodeList = new List.from(charCodes.take(end).skip(start),

runtime/vm/debugger_api_impl_test.cc

@@ -2230,9 +2230,10 @@ TEST_CASE(Debug_GetSupertype) {
   {
     Dart_Handle set_type = Dart_GetType(core_lib, set_name, 0, NULL);
     Dart_Handle super_type = Dart_GetSupertype(set_type);
+    Dart_Handle super2_type = Dart_GetSupertype(super_type);
     Dart_Handle iterable_type = Dart_GetType(core_lib, iterable_name, 0, NULL);
     const Type& expected_type = Api::UnwrapTypeHandle(zone, iterable_type);
-    const Type& actual_type = Api::UnwrapTypeHandle(zone, super_type);
+    const Type& actual_type = Api::UnwrapTypeHandle(zone, super2_type);
     EXPECT(expected_type.raw() == actual_type.raw());
   }
   {

sdk/lib/_internal/js_runtime/lib/collection_patch.dart

@@ -431,8 +431,7 @@ class _CustomHashMap<K, V> extends _HashMap<K, V> {
   String toString() => Maps.mapToString(this);
 }
 
-class _HashMapKeyIterable<E> extends Iterable<E>
-                             implements EfficientLength {
+class _HashMapKeyIterable<E> extends EfficientLengthIterable<E> {
   final _map;
   _HashMapKeyIterable(this._map);
 
@@ -664,8 +663,7 @@ class _Es6LinkedIdentityHashMap<K, V>
   String toString() => Maps.mapToString(this);
 }
 
-class _Es6MapIterable<E> extends Iterable<E>
-                         implements EfficientLength {
+class _Es6MapIterable<E> extends EfficientLengthIterable<E> {
   final _map;
   final bool _isKeys;
 

sdk/lib/_internal/js_runtime/lib/js_array.dart

@@ -146,7 +146,7 @@ class JSArray<E> extends Interceptor implements List<E>, JSIndexable {
   void insertAll(int index, Iterable<E> iterable) {
     checkGrowable('insertAll');
     RangeError.checkValueInInterval(index, 0, this.length, "index");
-    if (iterable is! EfficientLength) {
+    if (iterable is! EfficientLengthIterable) {
       iterable = iterable.toList();
     }
     int insertionLength = iterable.length;
@@ -463,7 +463,7 @@ class JSArray<E> extends Interceptor implements List<E>, JSIndexable {
   void replaceRange(int start, int end, Iterable<E> replacement) {
     checkGrowable('replace range');
     RangeError.checkValidRange(start, end, this.length);
-    if (replacement is! EfficientLength) {
+    if (replacement is! EfficientLengthIterable) {
       replacement = replacement.toList();
     }
     int removeLength = end - start;

sdk/lib/_internal/js_runtime/lib/js_helper.dart

@@ -56,7 +56,7 @@ import 'dart:_foreign_helper' show
 import 'dart:_interceptors';
 import 'dart:_internal' as _symbol_dev;
 import 'dart:_internal' show
-    EfficientLength,
+    EfficientLengthIterable,
     MappedIterable,
     IterableElementError;
 

sdk/lib/_internal/js_runtime/lib/linked_hash_map.dart

@@ -380,8 +380,7 @@ class LinkedHashMapCell<K, V> {
   LinkedHashMapCell(this.hashMapCellKey, this.hashMapCellValue);
 }
 
-class LinkedHashMapKeyIterable<E> extends Iterable<E>
-    implements EfficientLength {
+class LinkedHashMapKeyIterable<E> extends EfficientLengthIterable<E> {
   final dynamic/*=JsLinkedHashMap<E, dynamic>*/ _map;
   LinkedHashMapKeyIterable(this._map);
 

sdk/lib/collection/iterable.dart

@@ -91,7 +91,7 @@ abstract class IterableMixin<E> implements Iterable<E> {
   Set<E> toSet() => new Set<E>.from(this);
 
   int get length {
-    assert(this is! EfficientLength);
+    assert(this is! EfficientLengthIterable);
     int count = 0;
     Iterator it = iterator;
     while (it.moveNext()) {

sdk/lib/collection/list.dart

@@ -395,7 +395,7 @@ abstract class ListMixin<E> implements List<E> {
 
   void replaceRange(int start, int end, Iterable<E> newContents) {
     RangeError.checkValidRange(start, end, this.length);
-    if (newContents is! EfficientLength) {
+    if (newContents is! EfficientLengthIterable) {
       newContents = newContents.toList();
     }
     int removeLength = end - start;
@@ -482,7 +482,7 @@ abstract class ListMixin<E> implements List<E> {
 
   void insertAll(int index, Iterable<E> iterable) {
     RangeError.checkValueInInterval(index, 0, length, "index");
-    if (iterable is! EfficientLength || identical(iterable, this)) {
+    if (iterable is! EfficientLengthIterable || identical(iterable, this)) {
       iterable = iterable.toList();
     }
     int insertionLength = iterable.length;

sdk/lib/collection/maps.dart

@@ -111,8 +111,7 @@ abstract class UnmodifiableMapBase<K, V> =
  * It accesses the values by iterating over the keys of the map, and using the
  * map's `operator[]` to lookup the keys.
  */
-class _MapBaseValueIterable<K, V> extends Iterable<V>
-                                  implements EfficientLength {
+class _MapBaseValueIterable<K, V> extends EfficientLengthIterable<V> {
   final Map<K, V> _map;
   _MapBaseValueIterable(this._map);
 

sdk/lib/collection/queue.dart

@@ -17,7 +17,7 @@ part of dart.collection;
  * This goes both for using the [iterator] directly, or for iterating an
  * `Iterable` returned by a method like [map] or [where].
  */
-abstract class Queue<E> implements Iterable<E>, EfficientLength {
+abstract class Queue<E> implements EfficientLengthIterable<E> {
 
   /**
    * Creates a queue.
@@ -487,7 +487,7 @@ class ListQueue<E> extends ListIterable<E> implements Queue<E> {
       return queue;
     } else {
       int capacity = _INITIAL_CAPACITY;
-      if (elements is EfficientLength) {
+      if (elements is EfficientLengthIterable) {
         capacity = elements.length;
       }
       ListQueue<E> result = new ListQueue<E>(capacity);

sdk/lib/collection/splay_tree.dart

@@ -607,8 +607,7 @@ abstract class _SplayTreeIterator<K, T> implements Iterator<T> {
   T _getValue(_SplayTreeNode<K> node);
 }
 
-class _SplayTreeKeyIterable<K> extends Iterable<K>
-                               implements EfficientLength {
+class _SplayTreeKeyIterable<K> extends EfficientLengthIterable<K> {
   _SplayTree<K, _SplayTreeNode<K>> _tree;
   _SplayTreeKeyIterable(this._tree);
   int get length => _tree._count;
@@ -624,8 +623,7 @@ class _SplayTreeKeyIterable<K> extends Iterable<K>
   }
 }
 
-class _SplayTreeValueIterable<K, V> extends Iterable<V>
-                                    implements EfficientLength {
+class _SplayTreeValueIterable<K, V> extends EfficientLengthIterable<V> {
   SplayTreeMap<K, V> _map;
   _SplayTreeValueIterable(this._map);
   int get length => _map._count;

sdk/lib/core/iterable.dart

@@ -368,7 +368,7 @@ abstract class Iterable<E> {
    * Some iterables have a more efficient way to find the number of elements.
    */
   int get length {
-    assert(this is! EfficientLength);
+    assert(this is! EfficientLengthIterable);
     int count = 0;
     Iterator it = iterator;
     while (it.moveNext()) {

sdk/lib/core/list.dart

@@ -51,7 +51,7 @@ part of dart.core;
  * directly or through iterating an [Iterable] that is backed by the list, will
  * break the iteration.
  */
-abstract class List<E> implements Iterable<E>, EfficientLength {
+abstract class List<E> implements EfficientLengthIterable<E> {
   /**
    * Creates a list of the given length.
    *

sdk/lib/core/set.dart

@@ -31,7 +31,7 @@ part of dart.core;
  * iterating either the set itself or any [Iterable] that is backed by the set,
  * such as the ones returned by methods like [where] and [map].
  */
-abstract class Set<E> extends Iterable<E> implements EfficientLength {
+abstract class Set<E> extends EfficientLengthIterable<E> {
   /**
    * Creates an empty [Set].
    *

sdk/lib/internal/iterable.dart

@@ -8,7 +8,8 @@ part of dart._internal;
  * Marker interface for [Iterable] subclasses that have an efficient
  * [length] implementation.
  */
-abstract class EfficientLength {
+abstract class EfficientLengthIterable<T> extends Iterable<T> {
+  const EfficientLengthIterable();
   /**
    * Returns the number of elements in the iterable.
    *
@@ -24,8 +25,7 @@ abstract class EfficientLength {
  * All other methods are implemented in terms of [length] and [elementAt],
  * including [iterator].
  */
-abstract class ListIterable<E> extends Iterable<E>
-                               implements EfficientLength {
+abstract class ListIterable<E> extends EfficientLengthIterable<E> {
   int get length;
   E elementAt(int i);
 
@@ -354,7 +354,7 @@ class MappedIterable<S, T> extends Iterable<T> {
   final _Transformation<S, T> _f;
 
   factory MappedIterable(Iterable<S> iterable, T function(S value)) {
-    if (iterable is EfficientLength) {
+    if (iterable is EfficientLengthIterable) {
       return new EfficientLengthMappedIterable<S, T>(iterable, function);
     }
     return new MappedIterable<S, T>._(iterable, function);
@@ -376,7 +376,7 @@ class MappedIterable<S, T> extends Iterable<T> {
 }
 
 class EfficientLengthMappedIterable<S, T> extends MappedIterable<S, T>
-                                          implements EfficientLength {
+    implements EfficientLengthIterable<T> {
   EfficientLengthMappedIterable(Iterable<S> iterable, T function(S value))
       : super._(iterable, function);
 }
@@ -406,7 +406,7 @@ class MappedIterator<S, T> extends Iterator<T> {
  * Expects efficient `length` and `elementAt` on the source iterable.
  */
 class MappedListIterable<S, T> extends ListIterable<T>
-                               implements EfficientLength {
+                               implements EfficientLengthIterable<T> {
   final Iterable<S> _source;
   final _Transformation<S, T> _f;
 
@@ -427,7 +427,7 @@ class WhereIterable<E> extends Iterable<E> {
 
   Iterator<E> get iterator => new WhereIterator<E>(_iterable.iterator, _f);
 
-  // Specialization of [Iterable.map] to non-EfficientLength.
+  // Specialization of [Iterable.map] to non-EfficientLengthIterable.
   Iterable/*<T>*/ map/*<T>*/(/*=T*/ f(E element)) =>
      new MappedIterable<E, dynamic/*=T*/>._(this, f);
 }
@@ -500,7 +500,7 @@ class TakeIterable<E> extends Iterable<E> {
     if (takeCount is! int || takeCount < 0) {
       throw new ArgumentError(takeCount);
     }
-    if (iterable is EfficientLength) {
+    if (iterable is EfficientLengthIterable) {
       return new EfficientLengthTakeIterable<E>(iterable, takeCount);
     }
     return new TakeIterable<E>._(iterable, takeCount);
@@ -514,7 +514,7 @@ class TakeIterable<E> extends Iterable<E> {
 }
 
 class EfficientLengthTakeIterable<E> extends TakeIterable<E>
-                                     implements EfficientLength {
+                                     implements EfficientLengthIterable<E> {
   EfficientLengthTakeIterable(Iterable<E> iterable, int takeCount)
       : super._(iterable, takeCount);
 
@@ -587,7 +587,7 @@ class SkipIterable<E> extends Iterable<E> {
   final int _skipCount;
 
   factory SkipIterable(Iterable<E> iterable, int count) {
-    if (iterable is EfficientLength) {
+    if (iterable is EfficientLengthIterable) {
       return new EfficientLengthSkipIterable<E>(iterable, count);
     }
     return new SkipIterable<E>._(iterable, count);
@@ -614,7 +614,7 @@ class SkipIterable<E> extends Iterable<E> {
 }
 
 class EfficientLengthSkipIterable<E> extends SkipIterable<E>
-                                     implements EfficientLength {
+                                     implements EfficientLengthIterable<E> {
   EfficientLengthSkipIterable(Iterable<E> iterable, int skipCount)
       : super._(iterable, skipCount);
 
@@ -676,7 +676,7 @@ class SkipWhileIterator<E> extends Iterator<E> {
 /**
  * The always empty [Iterable].
  */
-class EmptyIterable<E> extends Iterable<E> implements EfficientLength {
+class EmptyIterable<E> extends EfficientLengthIterable<E> {
   const EmptyIterable();
 
   Iterator<E> get iterator => const EmptyIterator();

tests/corelib/growable_list_test.dart

@@ -34,7 +34,7 @@ class TestIterable extends TestIterableBase {
   int get length => throw "SHOULD NOT BE CALLED";
 }
 
-// Implement Set for private EfficientLength interface.
+// Implement Set for private EfficientLengthIterable interface.
 class EfficientTestIterable extends TestIterableBase
                             implements Set<int> {
   EfficientTestIterable(length, count, [callbackIndex = -1, callback])
@@ -104,7 +104,7 @@ void testConstructor() {
 }
 
 void testConcurrentModification() {
-  // Without EfficientLength interface
+  // Without EfficientLengthIterable interface
   {
     // Change length of list after 200 additions.
     var l = [];
@@ -127,7 +127,7 @@ void testConcurrentModification() {
     }, (e) => e is ConcurrentModificationError, "cm2");
   }
 
-  // With EfficientLength interface (uses length).
+  // With EfficientLengthIterable interface (uses length).
   {
     // Change length of list after 20 additions.
     var l = [];

tests/language/efficient_length_warning_test.dart

@@ -0,0 +1,16 @@
+// 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.
+// Third dart test program.
+
+import "dart:math";
+
+main() {
+  // This should no longer cause a warning because the least-upper-bound
+  // of List<int> and Set<int> is Object.
+  // The LUB is now EfficientLengthIterable and it extends Iterable.
+  var x = (new Random().nextBool() // Unpredictable condition.
+      ? <int>[1]
+      : new Set<int>.from([1])).first;
+  if (x != 1) throw "Wat?";
+}