My regression tests for #513 have shown up the following inconsistency in existing f#:

printfn "%d" <| (ComparisonIdentity.Structural.Compare (SByte.MinValue, SByte.MaxValue))
printfn "%d" <| (ComparisonIdentity.Structural.Compare (Some SByte.MinValue, Some SByte.MaxValue))

Output

-1
-255

It is due to FSharpOption's type generic call to:

LanguagePrimitives.HashCompare.GenericComparisonWithComparerIntrinsic<T>(genericComparer, x, y);

Now I doubt if anyway is using comparers in any other way than < 0 or > 0, but they may be? #513 is a potentially breaking change because it returns -1 for the Option case - i.e. matching the primitive operation (although the affects of this breaking case, to Option comparison operations being sensitive to particular return values - is almost vanishingly small I would say..)

(The good news is that if in my regression limits Compare to (sign of Compare) then I'm getting no regression errors. I'll put my regression test up soon)