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public static int Count<TEnumerable, TEnumerator, TSource>(this TEnumerable source)
    where TEnumerable : IValueEnumerable<TSource, TEnumerator>
    where TEnumerator : struct, IEnumerator<TSource>
{
    var counter = 0;
    using var enumerator = source.GetEnumerator();
    checked
    {
        while (enumerator.MoveNext())
            counter++;

aalmada

public class Enumerable<T>
{
    public Enumerable<T> GetEnumerator() 
        => this;

    public T Current 
        => default;

    public bool MoveNext() 
        => default;

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public static int Count<TEnumerable, TEnumerator, TSource>(this TEnumerable source)
    where TEnumerable : IValueEnumerable<TSource, TEnumerator>
    where TEnumerator : struct, IEnumerator<TSource>
{
    using var enumerator = source.GetEnumerator();
    var count = 0;
    while (enumerator.MoveNext())
        count++;
    return count;
} 

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namespace NetFabric.Hyperlinq
{
    public interface IValueEnumerable<out T, out TEnumerator>
        : IEnumerable<T>
        where TEnumerator : struct, IEnumerator<T>
    {
        new TEnumerator GetEnumerator();
    }

    public interface IValueReadOnlyCollection<out T, out TEnumerator>

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public static Expression Using(ParameterExpression variable, Expression content)
{
    return variable.Type switch
    {
        {IsValueType: true} => ValueTypeUsing(variable, content),

        _ => ReferenceTypeUsing(variable, content)
    };

    static Expression ValueTypeUsing(Expression variable, Expression content)

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Array.Int32.ArrayInt32WhereCount

References:

• JM.LinqFaster: 1.1.2
• LinqAF: 3.0.0.0
• StructLinq.BCL: 0.19.1
• NetFabric.Hyperlinq: 3.0.0-beta26

Results:

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using BenchmarkDotNet.Attributes;
using System;
using System.Linq;

namespace ConsoleApp2
{
    [MemoryDiagnoser]
    [DisassemblyDiagnoser(printSource: true)]
    public class ArrayBenchmarks
    {

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using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Jobs;
using System.Linq;

namespace NetFabric.Hyperlinq.Benchmarks
{
    [SimpleJob(RuntimeMoniker.Net472, baseline: true)]
    [SimpleJob(RuntimeMoniker.NetCoreApp50)]
    [MemoryDiagnoser]
    public class RangeContainsBenchmarks

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public class RefEnumerationVariableAnalyzerTests : CodeFixVerifier
{
    protected override DiagnosticAnalyzer GetCSharpDiagnosticAnalyzer() 
        => new RefEnumerationVariableAnalyzer();

    protected override CodeFixProvider GetCSharpCodeFixProvider()
        => new RefEnumerationVariableCodeFixProvider();

    [Theory]
    [InlineData("TestData/HLQ004/NoDiagnostic/NoRef.cs")]

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  <ItemGroup>
    <Compile Remove="TestData\**\*.Fix.cs" />
  </ItemGroup>

  <ItemGroup>
    <Content Include="TestData\**\*.Fix.cs">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </Content>
  </ItemGroup>