ValueTuple.IStructuralComparable/Equatable throws NRE instead of ArgumentNullException

[hughbe]

The following tests demonstrates this.

[Fact]
public void IStructuralEquatable_Equals_NullEqualityComparer_ThrowsNullReferenceException()
{
    IStructuralEquatable structuralEquatable = ValueTuple.Create(1);
    Assert.Throws<NullReferenceException>(() => structuralEquatable.Equals(Tuple.Create(1), null));
}

[Fact]
public void IStructuralEquatable_GetHashCode_NullEqualityComparer_ThrowsNullReferenceException()
{
    IStructuralEquatable structuralEquatable = ValueTuple.Create(1);
    Assert.Throws<NullReferenceException>(() => structuralEquatable.GetHashCode(null));
}

[Fact]
public void IStructuralComparable_CompareTo_NullEqualityComparer_ThrowsNullReferenceException()
{
    IStructuralComparable structuralComparable = ValueTuple.Create(1);
    Assert.Throws<NullReferenceException>(() => structuralComparable.CompareTo(Tuple.Create(1), null));
}

Spun off from #19265

/cc @karelz (who can help triage this :) )

[karelz]

@terrajobst @weshaggard @stephentoub do we have room to tweak ValueTuple to follow the right patterns? I think we don't have the huge compatibility burden yet.

[weshaggard]

@jcouv would be able to talk to this

[jcouv]

@karelz Let me check with F# folks. I tried to keep ValueTuple as close as possible to Tuple for their purpose.

[jcouv]

Talked with @KevinRansom and he confirmed that matching the logic to System.Tuple should take precedence over any conventions (although reasonable), so that we facilitate users switching between Tuple and ValueTuple without having to remember to update their exception-checking code.

So we recommend resolving this issue as "by design".

[hughbe]

Awesome - I'll close this when I send in some tests documenting the behaviour