Boxing occurs when hashing a range - 200+ MB over a 90 seconds of normal IDE usage

[cartermp]

This was noticed in #6047 but not addressed in #6048

Although the range type overrides GetHashCode to call the hash function on two int64s, which specializes to that numeric type as you'd expect, the actual call chain ends up boxing the range type because it calls GenericHashIntrinsic:

https://github.com/Microsoft/visualfsharp/blob/44c7e10ca432d8f245a6d8f8e0ec19ca8c72edaf/src/fsharp/FSharp.Core/prim-types.fs#L1795

Ranges are hashed all of the time in normal IDE usage, including in various routines that will call hash directly or through the use of a distinct or groupBy function.

The net result was a few hundred MB in allocations over ~90 seconds of normal IDE usage.

[manofstick]

I believe #5307 should resolve this.

It should handle the generic cases (i.e. distinct, groupBy)...