Bad image when calling op_Addition on interface

[gusty]

Calling op_Addition on interface results in a Bad Image error.

Repro steps

1. open System.Numerics;;

2. IAdditionOperators.op_Addition (3, 6) ;;

Expected behavior

Compiles with val it: int = 9

Actual behavior

Fails compilation with:

> IAdditionOperators.op_Addition (3, 6) ;;
System.BadImageFormatException: Bad IL format.
   at <StartupCode$FSI_0012>.$FSI_0012.main@()
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
   at System.Reflection.MethodInvoker.Invoke(Object obj, IntPtr* args, BindingFlags invokeAttr)
Stopped due to error

Known workarounds

Don't call directly on the interface.

Related information

Other operations, like op_CheckedAddition work fine:

> IAdditionOperators.op_CheckedAddition (3, 6) ;;
val it: int = 9

Test on:

Microsoft (R) F# Interactive version 12.0.5.0 for F# 7.0

Microsoft Visual Studio Community 2022 (64-bit) - Preview
Version 17.4.0 Preview 2.1

[vzarytovskii]

Checked version is virtual member, and normal is abstract. I think it should be disallowed in general - calling methods directly on the interfaces, wdyt @dsyme?

[dsyme]

@vzarytovskii Curious, does C# allow this? I presume not? I assume we must be missing a check to disallow this?

[vzarytovskii]

@vzarytovskii Curious, does C# allow this? I presume not? I assume we must be missing a check to disallow this?

Nope, it doesn't for operators. It may for normal static methods with default implementation

[anpin]

I'm getting the same exception running this in fsi

dotnet fsi repro.fsx

/home/a/repro.fsx(4,3): warning FS3535: Declaring "interfaces with static abstract methods" is an advanced feature. See https://aka.ms/fsharp-iwsams for guidance. You can disable this warning by using '#nowarn "3535"' or '--nowarn:3535'.

System.BadImageFormatException: Bad IL format.
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
   at System.Reflection.MethodInvoker.Invoke(Object obj, IntPtr* args, BindingFlags invokeAttr)
Stopped due to error

open System

type x2<'a> =
  static abstract x2: 'a -> double

type random() =
  member _.next = Random.Shared.NextDouble()

  interface x2<random> with
    static member x2 __ = __.next * 2.0

random() |> x2.x2 |> printf "%A"

[vzarytovskii]

Just for historical reasons, this is why it's crashing (abstract vs virtual):
https://source.dot.net/#System.Private.CoreLib/src/libraries/System.Private.CoreLib/src/System/Numerics/IAdditionOperators.cs,5b77e6b404819054

Check will be introduced to ensure we generate call on virtual members, can't call abstracts.