ToFSharpFunc(Func) missing in .NET Core

[ruxo]

Hi,

I have an issue with using FuncConvert.ToFSharpFunc. For example:

let h = FuncConvert.ToFSharpFunc<int,int>

This will cause following compilation error:

error FS0502: The member or object constructor 'ToFSharpFunc' takes 1 type argument(s) but is here given 2. The required signature is 'static member FuncConvert.ToFSharpFunc : action:Action<'T> -> ('T -> unit)'

.NET CLI: 1.0.0-preview2-1-003177
Compiler Version: dotnet-compile-fsc/1.0.0-preview2-020000
dotNET Core Version: 1.1.0

[dsyme]

@ruxo Right now the overload set is different on FSharp.Core, the "Converter" overload is not available.

#if !FX_NO_CONVERTER
        /// <summary>Convert the given Converter delegate object to an F# function value</summary>
        /// <param name="converter">The input Converter.</param>
        /// <returns>The F# function.</returns>
        static member  ToFSharpFunc       : converter:Converter<'T,'U>          -> ('T -> 'U)
#endif

There does indeed need to be some kind of replacement for this overload using System.Func. We may need to use a different name to make sure we can provide it on .NET Framework too without breaking existing code.

[ruxo]

@dsyme Yes, I noticed that. But there exists another version that uses Func<T1,T2> instead. This one can be listed by reflection but cannot be resolved by the compiler.

[dsyme]

@ruxo Yes, you are correct that the Func version is not revealed in the signature. It should be

[dsyme]

@KevinRansom @cartermp My original proposed solution for this was to add Func-based overloads to the ToFSharpFunc API. It would be a nice addition however it's a breaking change for C# callers.

The approach I recommend is to keep the FuncConvert API the same as it has always been and to have a .NET Standard 2.0 build of FSharp.Core (where System.Converter is available).

I’ve forgotten – where are we on a .NET Standard 2.0 build of FSharp.Core?

[dsyme]

This is causing problems in practice, see #4470

@KevinRansom again mentioning that this strongly motivates having a .NET Standard 2.0-specific cut of FSharp.Core.

[cartermp]

@KevinRansom @dsyme let's pull the trigger on dropping netstandard1.6 support for FSharp.Core and unblocking this by making FSharp.Core netstandard2.0/net45 only. .NET Core 1.x is officially out of support starting July of this year, so there is no real reason for people to continue using F# vNext as a netstandard1.6 component.

We should also look at #6128 to see if it's related.

[realvictorprm]

so what is the status of this?

[cartermp]

#6814

[realvictorprm]

Nice, thank you @cartermp!