`Volatile.Read` can no longer read `ref` (instead it wants `inref`)

[radekm]

Please provide a succinct description of the issue.

Repro steps

I have a following global variable defined in a module

let currentData : Data ref = ref { Timestamp = DateTimeOffset.MinValue
                                   Foo = None
                                   Bar = []
                                 }

and I read its value in some function via Volatile.Read:

// `toJson` has type `Data -> byte array`.
let json = Data.toJson (Volatile.Read currentData)

Expected behavior

The code should type check (it type checked on net7 and also initially on net8).

Actual behavior

After updating .NET 8 it doesn't type check with error:

error FS0041: No overloads match for method 'Read'. Known type of argument: Data ref
Available overloads:
- Volatile.Read(location: inref<bool>) : bool // Argument 'location' doesn't match
- Volatile.Read(location: inref<byte>) : byte // Argument 'location' doesn't match
...
- Volatile.Read<'T when 'T: not struct>(location: inref<'T>) : 'T // Argument 'location' doesn't match

I think that the last mentioned overload should work but it seems that ref<Data> argument
can't be given to inref<Data> parameter.

Known workarounds

Don't know.

Related information

Provide any related information (optional):

• Tested under Windows, Linux, Mac (x86-64)
• Type checked on .NET 8.0.100, doesn't work on .NET 8.0.101
• Can it be related to 54d05be?

[vzarytovskii]

Duplicate of #16265
Fixed in #16232

[vzarytovskii]

Actually, let me double check, it. It sounds like a different issue. Though refs and byrefs are different things.

[radekm]

Is it really the same thing? Because #16265 says it has been fixed 2 days ago. But to me it seems the problem was just introduced.

[vzarytovskii]

Is it really the same thing? Because #16265 says it has been fixed 2 days ago. But to me it seems the problem was just introduced.

This problem was introduced with fix of dotnet/runtime#94317, not entirely sure what's happening.

[vzarytovskii]

@radekm

Immediate workaround would be to make it a byref:

open System;
open System.Threading
type Data = { Timestamp: DateTimeOffset }
let mutable currentData: Data  =
  { Timestamp = DateTimeOffset.MinValue }
let x = Volatile.Read &currentData

or

open System;
open System.Threading
type Data = { Timestamp: DateTimeOffset }
let mutable currentData: Data ref =
  ref { Timestamp = DateTimeOffset.MinValue }
let x = Volatile.Read &currentData

Until I figure out why don't we resolve the method anymore.