Use IList<> to improve performance

[viceroypenguin]

IList<> has better performance when using a for-loop, as long as .Count is cached before the start of the iteration. Update certain operators to use IList<> over ICollection<>/IEnumerable<>.

// * Summary *

BenchmarkDotNet v0.13.12, Windows 11 (10.0.22621.3447/22H2/2022Update/SunValley2)
12th Gen Intel Core i7-12700H, 1 CPU, 20 logical and 14 physical cores
.NET SDK 9.0.100-preview.3.24204.13
  [Host] : .NET 8.0.4 (8.0.424.16909), X64 RyuJIT AVX2

Method	source	Mean	Error	StdDev	Allocated
Foreach	Syste(...)nt32] [47]	797.1 μs	11.24 μs	10.52 μs	42 B
ForLoop	Syste(...)nt32] [47]	468.0 μs	3.35 μs	2.97 μs	1 B
ForLoopCache	Syste(...)nt32] [47]	416.6 μs	6.27 μs	5.87 μs	1 B
Foreach	Syste(...)nt32] [59]	3,272.8 μs	58.44 μs	54.66 μs	39 B
ForLoop	Syste(...)nt32] [59]	6,468.7 μs	74.49 μs	66.03 μs	15 B
ForLoopCache	Syste(...)nt32] [59]	3,292.2 μs	54.45 μs	48.27 μs	7 B
Foreach	Int32[1000000]	3,606.6 μs	43.21 μs	40.42 μs	39 B
ForLoop	Int32[1000000]	4,980.1 μs	50.78 μs	47.50 μs	15 B
ForLoopCache	Int32[1000000]	2,543.4 μs	23.93 μs	22.38 μs	7 B

Code

#load "BenchmarkDotNet"

void Main()
{
	RunBenchmark();
}

public IEnumerable<IList<int>> GetSources()
{
	var source = Enumerable.Range(1, 1_000_000);
	yield return source.ToArray();
	yield return source.ToList();
	yield return source.ToImmutableArray();
}

[Benchmark]
[ArgumentsSource(nameof(GetSources))]
public void Foreach(IList<int> source)
{
	var sum = 0;
	foreach (var i in source)
		sum += i;
}

[Benchmark]
[ArgumentsSource(nameof(GetSources))]
public void ForLoop(IList<int> source)
{
	var sum = 0;
	for (var i = 0; i < (uint)source.Count; i++)
		sum += source[i];
}

[Benchmark]
[ArgumentsSource(nameof(GetSources))]
public void ForLoopCache(IList<int> source)
{
	var sum = 0;
	var n = (uint)source.Count;
	for (var i = 0; i < n; i++)
		sum += source[i];
}

[tacosontitan]

What are these "certain operators" that need to be updated to use IList<>?