diff --git a/src/libraries/System.Linq/src/System.Linq.csproj b/src/libraries/System.Linq/src/System.Linq.csproj
index 2f93e584d18658..f032db1a303ee1 100644
--- a/src/libraries/System.Linq/src/System.Linq.csproj
+++ b/src/libraries/System.Linq/src/System.Linq.csproj
@@ -62,6 +62,7 @@
+
@@ -70,12 +71,10 @@
-
-
@@ -83,6 +82,7 @@
+
diff --git a/src/libraries/System.Linq/src/System/Linq/Count.cs b/src/libraries/System.Linq/src/System/Linq/Count.cs
index 6a12a11cbe163d..cd175cf6b9b3cc 100644
--- a/src/libraries/System.Linq/src/System/Linq/Count.cs
+++ b/src/libraries/System.Linq/src/System/Linq/Count.cs
@@ -20,7 +20,7 @@ public static int Count(this IEnumerable source)
return collectionoft.Count;
}
- if (!IsSizeOptimized && source is Iterator iterator)
+ if (source is Iterator iterator)
{
return iterator.GetCount(onlyIfCheap: false);
}
@@ -113,7 +113,7 @@ public static bool TryGetNonEnumeratedCount(this IEnumerable s
return true;
}
- if (!IsSizeOptimized && source is Iterator iterator)
+ if (source is Iterator iterator)
{
int c = iterator.GetCount(onlyIfCheap: true);
if (c >= 0)
diff --git a/src/libraries/System.Linq/src/System/Linq/ElementAt.cs b/src/libraries/System.Linq/src/System/Linq/ElementAt.cs
index 26c69366fa9f3b..f4dc1f23a16c80 100644
--- a/src/libraries/System.Linq/src/System/Linq/ElementAt.cs
+++ b/src/libraries/System.Linq/src/System/Linq/ElementAt.cs
@@ -23,7 +23,7 @@ public static TSource ElementAt(this IEnumerable source, int i
bool found;
TSource? element =
- !IsSizeOptimized && source is Iterator iterator ? iterator.TryGetElementAt(index, out found) :
+ source is Iterator iterator ? iterator.TryGetElementAt(index, out found) :
TryGetElementAtNonIterator(source, index, out found);
if (!found)
@@ -121,7 +121,7 @@ public static TSource ElementAt(this IEnumerable source, Index
}
return
- !IsSizeOptimized && source is Iterator iterator ? iterator.TryGetElementAt(index, out found) :
+ source is Iterator iterator ? iterator.TryGetElementAt(index, out found) :
TryGetElementAtNonIterator(source, index, out found);
}
diff --git a/src/libraries/System.Linq/src/System/Linq/Last.cs b/src/libraries/System.Linq/src/System/Linq/Last.cs
index ca48475259d8e5..c38604e397592f 100644
--- a/src/libraries/System.Linq/src/System/Linq/Last.cs
+++ b/src/libraries/System.Linq/src/System/Linq/Last.cs
@@ -69,7 +69,7 @@ public static TSource LastOrDefault(this IEnumerable source, F
}
return
- !IsSizeOptimized && source is Iterator iterator ? iterator.TryGetLast(out found) :
+ source is Iterator iterator ? iterator.TryGetLast(out found) :
TryGetLastNonIterator(source, out found);
}
diff --git a/src/libraries/System.Linq/src/System/Linq/OfType.SpeedOpt.cs b/src/libraries/System.Linq/src/System/Linq/OfType.SpeedOpt.cs
index 4420801ee4abcf..f2649e706c8a0e 100644
--- a/src/libraries/System.Linq/src/System/Linq/OfType.SpeedOpt.cs
+++ b/src/libraries/System.Linq/src/System/Linq/OfType.SpeedOpt.cs
@@ -167,7 +167,7 @@ public override IEnumerable Select(Func s
// they're covariant. It's not worthwhile checking for List to use the ListWhereSelectIterator
// because List<> is not covariant.
Func isTResult = static o => o is TResult;
- return objectSource is object[] array ?
+ return !IsSizeOptimized && objectSource is object[] array ?
new ArrayWhereSelectIterator(array, isTResult, localSelector) :
new IEnumerableWhereSelectIterator(objectSource, isTResult, localSelector);
}
@@ -177,7 +177,11 @@ public override IEnumerable Select(Func s
public override bool Contains(TResult value)
{
- if (!typeof(TResult).IsValueType && // don't box TResult
+ // Avoid checking for IList when size-optimized because it keeps IList
+ // implementations which may otherwise be trimmed. Since List implements
+ // IList and List is popular, this could potentially be a lot of code.
+ if (!IsSizeOptimized &&
+ !typeof(TResult).IsValueType && // don't box TResult
_source is IList list)
{
return list.Contains(value);
diff --git a/src/libraries/System.Linq/src/System/Linq/Select.SizeOpt.cs b/src/libraries/System.Linq/src/System/Linq/Select.SizeOpt.cs
new file mode 100644
index 00000000000000..bf476355511abd
--- /dev/null
+++ b/src/libraries/System.Linq/src/System/Linq/Select.SizeOpt.cs
@@ -0,0 +1,100 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace System.Linq
+{
+ public static partial class Enumerable
+ {
+ private sealed class SizeOptIListSelectIterator(IList _source, Func _selector)
+ : Iterator
+ {
+ private IEnumerator? _enumerator;
+
+ public override int GetCount(bool onlyIfCheap)
+ {
+ // In case someone uses Count() to force evaluation of
+ // the selector, run it provided `onlyIfCheap` is false.
+
+ if (onlyIfCheap)
+ {
+ return -1;
+ }
+
+ int count = 0;
+
+ foreach (TSource item in _source)
+ {
+ _selector(item);
+ checked
+ {
+ count++;
+ }
+ }
+
+ return count;
+ }
+
+ public override Iterator Skip(int count)
+ {
+ Debug.Assert(count > 0);
+ return new IListSkipTakeSelectIterator(_source, _selector, count, int.MaxValue);
+ }
+
+ public override Iterator Take(int count)
+ {
+ Debug.Assert(count > 0);
+ return new IListSkipTakeSelectIterator(_source, _selector, 0, count - 1);
+ }
+
+ public override bool MoveNext()
+ {
+ switch (_state)
+ {
+ case 1:
+ _enumerator = _source.GetEnumerator();
+ _state = 2;
+ goto case 2;
+ case 2:
+ Debug.Assert(_enumerator is not null);
+ if (_enumerator.MoveNext())
+ {
+ _current = _selector(_enumerator.Current);
+ return true;
+ }
+
+ Dispose();
+ break;
+ }
+
+ return false;
+ }
+
+ public override TResult[] ToArray()
+ {
+ TResult[] array = new TResult[_source.Count];
+ for (int i = 0; i < array.Length; i++)
+ {
+ array[i] = _selector(_source[i]);
+ }
+ return array;
+ }
+
+ public override List ToList()
+ {
+ List list = new List(_source.Count);
+ for (int i = 0; i < list.Count; i++)
+ {
+ list.Add(_selector(_source[i]));
+ }
+ return list;
+ }
+
+ private protected override Iterator Clone()
+ => new SizeOptIListSelectIterator(_source, _selector);
+ }
+ }
+}
diff --git a/src/libraries/System.Linq/src/System/Linq/Select.cs b/src/libraries/System.Linq/src/System/Linq/Select.cs
index ac27c8dda22eeb..d5fcb864384440 100644
--- a/src/libraries/System.Linq/src/System/Linq/Select.cs
+++ b/src/libraries/System.Linq/src/System/Linq/Select.cs
@@ -32,7 +32,9 @@ public static IEnumerable Select(
// don't need more code, just more data structures describing the new types).
if (IsSizeOptimized && typeof(TResult).IsValueType)
{
- return new IEnumerableSelectIterator(iterator, selector);
+ return source is IList il
+ ? new SizeOptIListSelectIterator(il, selector)
+ : new IEnumerableSelectIterator(iterator, selector);
}
else
{
@@ -42,6 +44,11 @@ public static IEnumerable Select(
if (source is IList ilist)
{
+ if (IsSizeOptimized)
+ {
+ return new SizeOptIListSelectIterator(ilist, selector);
+ }
+
if (source is TSource[] array)
{
if (array.Length == 0)
diff --git a/src/libraries/System.Linq/src/System/Linq/Skip.SizeOpt.cs b/src/libraries/System.Linq/src/System/Linq/Skip.SizeOpt.cs
deleted file mode 100644
index 13e6642ee1fc02..00000000000000
--- a/src/libraries/System.Linq/src/System/Linq/Skip.SizeOpt.cs
+++ /dev/null
@@ -1,20 +0,0 @@
-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-
-using System.Collections.Generic;
-
-namespace System.Linq
-{
- public static partial class Enumerable
- {
- private static IEnumerable SizeOptimizedSkipIterator(IEnumerable source, int count)
- {
- using IEnumerator e = source.GetEnumerator();
- while (count > 0 && e.MoveNext()) count--;
- if (count <= 0)
- {
- while (e.MoveNext()) yield return e.Current;
- }
- }
- }
-}
diff --git a/src/libraries/System.Linq/src/System/Linq/Skip.cs b/src/libraries/System.Linq/src/System/Linq/Skip.cs
index ac8252a07c6d0c..4e76f1afba9794 100644
--- a/src/libraries/System.Linq/src/System/Linq/Skip.cs
+++ b/src/libraries/System.Linq/src/System/Linq/Skip.cs
@@ -30,12 +30,12 @@ public static IEnumerable Skip(this IEnumerable sourc
count = 0;
}
- else if (!IsSizeOptimized && source is Iterator iterator)
+ else if (source is Iterator iterator)
{
return iterator.Skip(count) ?? Empty();
}
- return IsSizeOptimized ? SizeOptimizedSkipIterator(source, count) : SpeedOptimizedSkipIterator(source, count);
+ return SpeedOptimizedSkipIterator(source, count);
}
public static IEnumerable SkipWhile(this IEnumerable source, Func predicate)
diff --git a/src/libraries/System.Linq/src/System/Linq/Take.SizeOpt.cs b/src/libraries/System.Linq/src/System/Linq/Take.SizeOpt.cs
deleted file mode 100644
index 6f2bd0d9b0fa6b..00000000000000
--- a/src/libraries/System.Linq/src/System/Linq/Take.SizeOpt.cs
+++ /dev/null
@@ -1,47 +0,0 @@
-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-
-using System.Collections.Generic;
-using System.Diagnostics;
-
-namespace System.Linq
-{
- public static partial class Enumerable
- {
- private static IEnumerable SizeOptimizedTakeIterator(IEnumerable source, int count)
- {
- Debug.Assert(count > 0);
-
- foreach (TSource element in source)
- {
- yield return element;
- if (--count == 0) break;
- }
- }
-
- private static IEnumerable SizeOptimizedTakeRangeIterator(IEnumerable source, int startIndex, int endIndex)
- {
- Debug.Assert(source is not null);
- Debug.Assert(startIndex >= 0 && startIndex < endIndex);
-
- using IEnumerator e = source.GetEnumerator();
-
- int index = 0;
- while (index < startIndex && e.MoveNext())
- {
- ++index;
- }
-
- if (index < startIndex)
- {
- yield break;
- }
-
- while (index < endIndex && e.MoveNext())
- {
- yield return e.Current;
- ++index;
- }
- }
- }
-}
diff --git a/src/libraries/System.Linq/src/System/Linq/Take.cs b/src/libraries/System.Linq/src/System/Linq/Take.cs
index 9df5fbc8a2bec8..8d6ad9acb3998d 100644
--- a/src/libraries/System.Linq/src/System/Linq/Take.cs
+++ b/src/libraries/System.Linq/src/System/Linq/Take.cs
@@ -20,7 +20,7 @@ public static IEnumerable Take(this IEnumerable sourc
return [];
}
- return IsSizeOptimized ? SizeOptimizedTakeIterator(source, count) : SpeedOptimizedTakeIterator(source, count);
+ return SpeedOptimizedTakeIterator(source, count);
}
/// Returns a specified range of contiguous elements from a sequence.
@@ -68,7 +68,7 @@ public static IEnumerable Take(this IEnumerable sourc
return [];
}
- return IsSizeOptimized ? SizeOptimizedTakeRangeIterator(source, startIndex, endIndex) : SpeedOptimizedTakeRangeIterator(source, startIndex, endIndex);
+ return SpeedOptimizedTakeRangeIterator(source, startIndex, endIndex);
}
return TakeRangeFromEndIterator(source, isStartIndexFromEnd, startIndex, isEndIndexFromEnd, endIndex);
@@ -94,9 +94,7 @@ private static IEnumerable TakeRangeFromEndIterator(IEnumerabl
if (startIndex < endIndex)
{
- IEnumerable rangeIterator = IsSizeOptimized
- ? SizeOptimizedTakeRangeIterator(source, startIndex, endIndex)
- : SpeedOptimizedTakeRangeIterator(source, startIndex, endIndex);
+ IEnumerable rangeIterator = SpeedOptimizedTakeRangeIterator(source, startIndex, endIndex);
foreach (TSource element in rangeIterator)
{
yield return element;
diff --git a/src/libraries/System.Linq/src/System/Linq/Where.SizeOpt.cs b/src/libraries/System.Linq/src/System/Linq/Where.SizeOpt.cs
new file mode 100644
index 00000000000000..ebb94853261d81
--- /dev/null
+++ b/src/libraries/System.Linq/src/System/Linq/Where.SizeOpt.cs
@@ -0,0 +1,114 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace System.Linq
+{
+ public static partial class Enumerable
+ {
+ private sealed partial class SizeOptIListWhereIterator : Iterator
+ {
+ private readonly IList _source;
+ private readonly Func _predicate;
+ private IEnumerator? _enumerator;
+
+ public SizeOptIListWhereIterator(IList source, Func predicate)
+ {
+ Debug.Assert(source is not null);
+ Debug.Assert(predicate is not null);
+ _source = source;
+ _predicate = predicate;
+ }
+
+ private protected override Iterator Clone() =>
+ new SizeOptIListWhereIterator(_source, _predicate);
+
+ public override bool MoveNext()
+ {
+ switch (_state)
+ {
+ case 1:
+ _enumerator = _source.GetEnumerator();
+ _state = 2;
+ goto case 2;
+ case 2:
+ while (_enumerator!.MoveNext())
+ {
+ TSource item = _enumerator.Current;
+ if (_predicate(item))
+ {
+ _current = item;
+ return true;
+ }
+ }
+
+ Dispose();
+ break;
+ }
+
+ return false;
+ }
+
+ public override IEnumerable Where(Func predicate) =>
+ new SizeOptIListWhereIterator(_source, Utilities.CombinePredicates(_predicate, predicate));
+
+ public override TSource[] ToArray()
+ {
+ SegmentedArrayBuilder.ScratchBuffer scratch = default;
+ SegmentedArrayBuilder builder = new(scratch);
+
+ foreach (TSource item in _source)
+ {
+ if (_predicate(item))
+ {
+ builder.Add(item);
+ }
+ }
+
+ TSource[] result = builder.ToArray();
+ builder.Dispose();
+
+ return result;
+ }
+
+ public override List ToList()
+ {
+ SegmentedArrayBuilder.ScratchBuffer scratch = default;
+ SegmentedArrayBuilder builder = new(scratch);
+
+ foreach (TSource item in _source)
+ {
+ if (_predicate(item))
+ {
+ builder.Add(item);
+ }
+ }
+
+ List result = builder.ToList();
+ builder.Dispose();
+
+ return result;
+ }
+
+ public override int GetCount(bool onlyIfCheap)
+ {
+ if (onlyIfCheap)
+ {
+ return -1;
+ }
+
+ int count = 0;
+ foreach (TSource item in _source)
+ {
+ if (_predicate(item))
+ {
+ checked { count++; }
+ }
+ }
+ return count;
+ }
+ }
+ }
+}
diff --git a/src/libraries/System.Linq/src/System/Linq/Where.cs b/src/libraries/System.Linq/src/System/Linq/Where.cs
index 4371af8299fb2e..c0028a1c004a22 100644
--- a/src/libraries/System.Linq/src/System/Linq/Where.cs
+++ b/src/libraries/System.Linq/src/System/Linq/Where.cs
@@ -26,6 +26,12 @@ public static IEnumerable Where(this IEnumerable sour
return iterator.Where(predicate);
}
+ // Only use IList when size-optimizing (no array or List specializations).
+ if (IsSizeOptimized && source is IList sourceList)
+ {
+ return new SizeOptIListWhereIterator(sourceList, predicate);
+ }
+
if (source is TSource[] array)
{
if (array.Length == 0)
@@ -143,7 +149,7 @@ public override IEnumerable Select(Func sele
new IEnumerableWhereSelectIterator(_source, _predicate, selector);
public override IEnumerable Where(Func predicate) =>
- new IEnumerableWhereIterator(_source, CombinePredicates(_predicate, predicate));
+ new IEnumerableWhereIterator(_source, Utilities.CombinePredicates(_predicate, predicate));
}
///
diff --git a/src/libraries/System.Linq/tests/CountTests.cs b/src/libraries/System.Linq/tests/CountTests.cs
index ddf96d4cf4b59a..27b18f77870218 100644
--- a/src/libraries/System.Linq/tests/CountTests.cs
+++ b/src/libraries/System.Linq/tests/CountTests.cs
@@ -3,10 +3,11 @@
using System.Collections.Generic;
using Xunit;
+using Xunit.Abstractions;
namespace System.Linq.Tests
{
- public class CountTests : EnumerableTests
+ public class CountTests(ITestOutputHelper output) : EnumerableTests
{
[Fact]
public void SameResultsRepeatCallsIntQuery()
@@ -151,6 +152,7 @@ public void NonEnumeratedCount_SupportedEnumerables_ShouldReturnExpectedCount
[MemberData(nameof(NonEnumeratedCount_UnsupportedEnumerables))]
public void NonEnumeratedCount_UnsupportedEnumerables_ShouldReturnFalse(IEnumerable source)
{
+ output.WriteLine(source.GetType().FullName);
Assert.False(source.TryGetNonEnumeratedCount(out int actualCount));
Assert.Equal(0, actualCount);
}
@@ -180,15 +182,15 @@ public static IEnumerable NonEnumeratedCount_SupportedEnumerables()
yield return WrapArgs(100, Enumerable.Range(1, 100));
yield return WrapArgs(80, Enumerable.Repeat(1, 80));
+ yield return WrapArgs(20, Enumerable.Range(1, 20).Reverse());
+ yield return WrapArgs(20, Enumerable.Range(1, 20).OrderBy(x => -x));
+ yield return WrapArgs(20, Enumerable.Range(1, 10).Concat(Enumerable.Range(11, 10)));
if (PlatformDetection.IsLinqSpeedOptimized)
{
yield return WrapArgs(50, Enumerable.Range(1, 50).Select(x => x + 1));
yield return WrapArgs(4, new int[] { 1, 2, 3, 4 }.Select(x => x + 1));
yield return WrapArgs(50, Enumerable.Range(1, 50).Select(x => x + 1).Select(x => x - 1));
- yield return WrapArgs(20, Enumerable.Range(1, 20).Reverse());
- yield return WrapArgs(20, Enumerable.Range(1, 20).OrderBy(x => -x));
- yield return WrapArgs(20, Enumerable.Range(1, 10).Concat(Enumerable.Range(11, 10)));
}
static object[] WrapArgs(int expectedCount, IEnumerable source) => [expectedCount, source];
@@ -204,11 +206,8 @@ public static IEnumerable NonEnumeratedCount_UnsupportedEnumerables()
if (!PlatformDetection.IsLinqSpeedOptimized)
{
yield return WrapArgs(Enumerable.Range(1, 50).Select(x => x + 1));
- yield return WrapArgs(new int[] { 1, 2, 3, 4 }.Select(x => x + 1));
+ yield return WrapArgs(new int[] { 1, 2, 3, 4 }.Select(x => x + 1));
yield return WrapArgs(Enumerable.Range(1, 50).Select(x => x + 1).Select(x => x - 1));
- yield return WrapArgs(Enumerable.Range(1, 20).Reverse());
- yield return WrapArgs(Enumerable.Range(1, 20).OrderBy(x => -x));
- yield return WrapArgs(Enumerable.Range(1, 10).Concat(Enumerable.Range(11, 10)));
}
static object[] WrapArgs(IEnumerable source) => [source];
diff --git a/src/libraries/System.Linq/tests/OrderedSubsetting.cs b/src/libraries/System.Linq/tests/OrderedSubsetting.cs
index 5804ac1d4229e7..7826fb338dbce5 100644
--- a/src/libraries/System.Linq/tests/OrderedSubsetting.cs
+++ b/src/libraries/System.Linq/tests/OrderedSubsetting.cs
@@ -224,7 +224,7 @@ public void TakeAndSkip()
Assert.Equal(Enumerable.Range(10, 1), ordered.Take(11).Skip(10));
}
- [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsLinqSpeedOptimized))]
+ [Fact]
public void TakeAndSkip_DoesntIterateRangeUnlessNecessary()
{
Assert.Empty(Enumerable.Range(0, int.MaxValue).Take(int.MaxValue).OrderBy(i => i).Skip(int.MaxValue - 4).Skip(15));
diff --git a/src/libraries/System.Linq/tests/RangeTests.cs b/src/libraries/System.Linq/tests/RangeTests.cs
index 476d4804fefeef..0bb6acca8bc685 100644
--- a/src/libraries/System.Linq/tests/RangeTests.cs
+++ b/src/libraries/System.Linq/tests/RangeTests.cs
@@ -236,7 +236,7 @@ public void LastOrDefault()
Assert.Equal(int.MaxValue - 101, GetRange(-100, int.MaxValue).LastOrDefault());
}
- [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsLinqSpeedOptimized))]
+ [Fact]
public void IListImplementationIsValid()
{
Validate(GetRange(42, 10), [42, 43, 44, 45, 46, 47, 48, 49, 50, 51]);
diff --git a/src/libraries/System.Linq/tests/SelectTests.cs b/src/libraries/System.Linq/tests/SelectTests.cs
index c7c84565485c73..5fdae70d06df38 100644
--- a/src/libraries/System.Linq/tests/SelectTests.cs
+++ b/src/libraries/System.Linq/tests/SelectTests.cs
@@ -12,6 +12,32 @@ namespace System.Linq.Tests
{
public class SelectTests : EnumerableTests
{
+ [Fact]
+ public void SelectSideEffectsExecutedOnCount()
+ {
+ int i = 0;
+ // If we made no promises about side effects, i could be 0, but in practice users have
+ // taken a dependency on side effects executing on Count.
+ var count = Enumerable.Range(1, 10).Select(x => i++).Count();
+ Assert.Equal(10, count);
+ Assert.Equal(10, i);
+
+ i = 0;
+ count = Enumerable.Range(1, 10).Skip(5).Select(x => i++).Count();
+ Assert.Equal(5, count);
+ Assert.Equal(5, i);
+
+ i = 0;
+ count = Enumerable.Range(1, 10).Take(5).Select(x => i++).Count();
+ Assert.Equal(5, count);
+ Assert.Equal(5, i);
+
+ i = 0;
+ count = Enumerable.Range(1, 10).Skip(2).Take(3).Select(x => i++).Count();
+ Assert.Equal(3, count);
+ Assert.Equal(3, i);
+ }
+
[Fact]
public void SameResultsRepeatCallsStringQuery()
{
diff --git a/src/libraries/System.Linq/tests/TakeTests.cs b/src/libraries/System.Linq/tests/TakeTests.cs
index bcdaa42df0a9b5..310a942e507feb 100644
--- a/src/libraries/System.Linq/tests/TakeTests.cs
+++ b/src/libraries/System.Linq/tests/TakeTests.cs
@@ -669,7 +669,7 @@ public void RepeatEnumerating()
}
}
- [ConditionalTheory(typeof(PlatformDetection), nameof(PlatformDetection.IsLinqSpeedOptimized))]
+ [Theory]
[InlineData(1000)]
[InlineData(1000000)]
[InlineData(int.MaxValue)]
@@ -1623,7 +1623,7 @@ public void EmptySource_DoNotThrowException_EnumerablePartition()
Assert.Empty(EnumerablePartitionOrEmpty(source).Take(^6..^7));
}
- [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsLinqSpeedOptimized))]
+ [Fact]
public void SkipTakeOnIListIsIList()
{
IList list = new ReadOnlyCollection(Enumerable.Range(0, 100).ToList());
diff --git a/src/libraries/tests.proj b/src/libraries/tests.proj
index da8efe5407d1a0..fdf07d02406ad4 100644
--- a/src/libraries/tests.proj
+++ b/src/libraries/tests.proj
@@ -574,6 +574,7 @@
+