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Improve ImmutableArrayExtensions.SequenceEqual #118932

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28c3ad9
Improve ImmutableArrayExtensions.SequenceEqual
prozolic Aug 20, 2025
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Remove BOM
prozolic Aug 20, 2025
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Update src/libraries/System.Collections.Immutable/src/System/Linq/Imm…
prozolic Aug 21, 2025
87d2080
Replace manual implementation with Enumerable.SequenceEqual
prozolic Aug 22, 2025
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Optimize ImmutableArrayExtensions.SequenceEqual with ICollection<T> f…
prozolic Aug 23, 2025
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Update src/libraries/System.Collections.Immutable/src/System/Linq/Imm…
prozolic Aug 28, 2025
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Merge branch 'main' into ImmutableArrayExtensions.SequenceEqual
prozolic Aug 30, 2025
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Merge branch 'main' into ImmutableArrayExtensions.SequenceEqual
pavelsavara Sep 1, 2025
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Merge branch 'main' into ImmutableArrayExtensions.SequenceEqual
prozolic Sep 17, 2025
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Merge branch 'main' into ImmutableArrayExtensions.SequenceEqual
prozolic Sep 20, 2025
15602a6
Update src/libraries/System.Collections.Immutable/src/System/Linq/Imm…
prozolic Sep 20, 2025
37863da
Rename local method from Impl to Enumerate
prozolic Sep 20, 2025
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Merge branch 'main' into ImmutableArrayExtensions.SequenceEqual
prozolic Oct 22, 2025
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Add tests for non-collection path in ImmutableArrayExtensions.Sequenc…
prozolic Dec 4, 2025
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Merge branch 'main' into ImmutableArrayExtensions.SequenceEqual
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39 changes: 25 additions & 14 deletions src/libraries/System.Collections.Immutable/src/System/Linq/ImmutableArrayExtensions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -187,28 +187,39 @@ public static bool SequenceEqual<TDerived, TBase>(this ImmutableArray<TBase> imm
/// <typeparam name="TBase">The type of element contained by the collection.</typeparam>
public static bool SequenceEqual<TDerived, TBase>(this ImmutableArray<TBase> immutableArray, IEnumerable<TDerived> items, IEqualityComparer<TBase>? comparer = null) where TDerived : TBase
{
Requires.NotNull(items, nameof(items));
if (items is ICollection<TBase> itemsCol)
{
immutableArray.ThrowNullRefIfNotInitialized();
return Enumerable.SequenceEqual(immutableArray.array, itemsCol, comparer);
}

comparer ??= EqualityComparer<TBase>.Default;
return Enumerate(immutableArray, items, comparer);

int i = 0;
int n = immutableArray.Length;
foreach (TDerived item in items)
static bool Enumerate(ImmutableArray<TBase> immutableArray, IEnumerable<TDerived> items, IEqualityComparer<TBase>? comparer)
{
if (i == n)
{
return false;
}
Requires.NotNull(items, nameof(items));

if (!comparer.Equals(immutableArray[i], item))
comparer ??= EqualityComparer<TBase>.Default;

int i = 0;
int n = immutableArray.Length;
foreach (TDerived item in items)
{
return false;
if (i == n)
{
return false;
}

if (!comparer.Equals(immutableArray[i], item))
{
return false;
}

i++;
}

i++;
return i == n;
}

return i == n;
}

/// <summary>
Expand Down
28 changes: 28 additions & 0 deletions src/libraries/System.Collections.Immutable/tests/ImmutableArrayExtensionsTest.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,14 @@ public class ImmutableArrayExtensionsTest
private static readonly ImmutableArray<int>.Builder s_oneElementBuilder = ImmutableArray.Create<int>(1).ToBuilder();
private static readonly ImmutableArray<int>.Builder s_manyElementsBuilder = ImmutableArray.Create<int>(1, 2, 3).ToBuilder();

private IEnumerable<T> ToEnumerable<T>(ImmutableArray<T> array)
{
foreach (T item in array)
{
yield return item;
}
}

[Fact]
public void Select()
{
Expand Down Expand Up @@ -146,6 +154,11 @@ public void SequenceEqual()
Assert.False(ImmutableArrayExtensions.SequenceEqual(s_manyElements, (IEnumerable<int>)s_manyElements.Add(1).ToArray(), comparer));
Assert.False(ImmutableArrayExtensions.SequenceEqual(s_manyElements.Add(1), s_manyElements.Add(2).ToArray(), comparer));
Assert.False(ImmutableArrayExtensions.SequenceEqual(s_manyElements.Add(1), (IEnumerable<int>)s_manyElements.Add(2).ToArray(), comparer));

Assert.True(ImmutableArrayExtensions.SequenceEqual(s_manyElements, ToEnumerable(s_manyElements), comparer));
Assert.False(ImmutableArrayExtensions.SequenceEqual(s_manyElements, ToEnumerable(s_oneElement), comparer));
Assert.False(ImmutableArrayExtensions.SequenceEqual(s_manyElements, ToEnumerable(s_manyElements.Add(1)), comparer));
Assert.False(ImmutableArrayExtensions.SequenceEqual(s_manyElements.Add(1), ToEnumerable(s_manyElements.Add(2)), comparer));
}

Assert.True(ImmutableArrayExtensions.SequenceEqual(s_manyElements, s_manyElements, (a, b) => true));
Expand All @@ -164,6 +177,9 @@ public void SequenceEqualEmptyDefault()
TestExtensionsMethods.ValidateDefaultThisBehavior(() => ImmutableArrayExtensions.SequenceEqual(s_oneElement, s_emptyDefault));
TestExtensionsMethods.ValidateDefaultThisBehavior(() => ImmutableArrayExtensions.SequenceEqual(s_emptyDefault, s_empty));
TestExtensionsMethods.ValidateDefaultThisBehavior(() => ImmutableArrayExtensions.SequenceEqual(s_emptyDefault, s_emptyDefault));
TestExtensionsMethods.ValidateDefaultThisBehavior(() => ImmutableArrayExtensions.SequenceEqual(s_oneElement, ToEnumerable(s_emptyDefault)));
TestExtensionsMethods.ValidateDefaultThisBehavior(() => ImmutableArrayExtensions.SequenceEqual(s_emptyDefault, ToEnumerable(s_empty)));
TestExtensionsMethods.ValidateDefaultThisBehavior(() => ImmutableArrayExtensions.SequenceEqual(s_emptyDefault, ToEnumerable(s_emptyDefault)));
AssertExtensions.Throws<ArgumentNullException>("predicate", () => ImmutableArrayExtensions.SequenceEqual(s_emptyDefault, s_emptyDefault, (Func<int, int, bool>)null));
}

Expand All @@ -173,10 +189,22 @@ public void SequenceEqualEmpty()
AssertExtensions.Throws<ArgumentNullException>("items", () => ImmutableArrayExtensions.SequenceEqual(s_empty, (IEnumerable<int>)null));
Assert.True(ImmutableArrayExtensions.SequenceEqual(s_empty, s_empty));
Assert.True(ImmutableArrayExtensions.SequenceEqual(s_empty, s_empty.ToArray()));
Assert.True(ImmutableArrayExtensions.SequenceEqual(s_empty, ToEnumerable(s_empty)));
Assert.True(ImmutableArrayExtensions.SequenceEqual(s_empty, s_empty, (a, b) => true));
Assert.True(ImmutableArrayExtensions.SequenceEqual(s_empty, s_empty, (a, b) => false));
}

[Fact]
public void SequenceEqualSingleElement()
{
Assert.True(ImmutableArrayExtensions.SequenceEqual(s_oneElement, s_oneElement));
Assert.False(ImmutableArrayExtensions.SequenceEqual(s_oneElement, s_empty));
Assert.False(ImmutableArrayExtensions.SequenceEqual(s_oneElement, s_manyElements));
Assert.True(ImmutableArrayExtensions.SequenceEqual(s_oneElement, ToEnumerable(s_oneElement)));
Assert.False(ImmutableArrayExtensions.SequenceEqual(s_oneElement, ToEnumerable(s_empty)));
Assert.False(ImmutableArrayExtensions.SequenceEqual(s_oneElement, ToEnumerable(s_manyElements)));
}

[Fact]
public void Aggregate()
{
Expand Down
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