Ionide-vscode-fsharp: Intellisense error in `build.fsx` file

[MangelMaxime]

I am not sure if this is something related to Ionide or Fake.

When I open the build.fsx of Thoth I get this following error. And the whole file is red.

The type 'IEquatable`1' is required here and is unavailable. You must add a reference to assembly 'netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'.

I am using latest version of Fake 5.0 and already had the problem with 5.0.0-rc018.244

Any ideas what is causing this problem ? And/or how to fix it ?

cc: @matthid

Machine infos

• Operating system: Darwin
• Arch: x64
• VSCode: 1.23.1
• Runtime: netcore
• Dotnet version: 2.1.300

[MangelMaxime]

Additional info:

I have another project using: Fake 5.0.0-rc016.225 and it's working fine.

Also, even if the intellisense is broken I can run build.fsx and it's working as expected.

[matthid]

See https://github.com/fsharp/FAKE/issues/1938 - workaround is quite simple.
The reason is that intellisense is using "full-framework" and not netcore/netstandard and in the full framework you need the reference.

[matthid]

Why was it working before with 5.0.0-rc016.225 did we had a new deps ?

I think it is because we introduced System.Reactive dependency in Fake.Core.Target

[MangelMaxime]

Ok I fixed the intellisense by adding:

#r "paket: groupref netcorebuild //"
#load ".fake/build.fsx/intellisense.fsx"
#if !FAKE
  #r "./packages/netcorebuild/NETStandard.Library.NETFramework/build/net461/lib/netstandard.dll"
#endif

And not just #r netstandard

[matthid]

Interesting because #r "netstandard" should work because it is a framework assembly. Just like #r "System.Anything" works ...

Interesting because if we ever fix this in paket I'm not sure what else then #r "netstandard" we could write.
@MangelMaxime Did you have any errors or was it just ignored? (IE did it hurt to add #r "netstandard"?

[MangelMaxime]

Using #r "netstandard just had no effect.

Using both seems to work fine:

#r "paket: groupref netcorebuild //"
#load ".fake/build.fsx/intellisense.fsx"
#if !FAKE
  #r "netstandard"
  #r "./packages/netcorebuild/NETStandard.Library.NETFramework/build/net461/lib/netstandard.dll"
#endif

However, I would prefer that #r "netstandard" works because here I needed to remove storage: none from paket.dependencies :)

[matthid]

@MangelMaxime what .net framework is installed on your system 4.7.2?

[MangelMaxime]

@matthid I have no idea.

I guess I have this frameworks installed:

➜  ~ ls $(dirname $(which mono))/../lib/mono/ 
2.0-api                   4.6.1-api                 lldb
3.5-api                   4.6.2-api                 mono-configuration-crypto
4.0                       4.7-api                   monodoc
4.0-api                   4.7.1-api                 msbuild
4.5                       Microsoft F#              nuget
4.5-api                   Microsoft SDKs            xbuild
4.5.1-api                 fsharp                    xbuild-frameworks
4.5.2-api                 gac
4.6-api                   gtk-sharp-2.0
➜  ~ 

[matthid]

Ah, so it might be a mono issue

[gerjandev]

Related https://github.com/fsharp/FAKE/issues/1985

Is there a final solution/fix?

[MangelMaxime]

Using the solution in: https://github.com/ionide/ionide-vscode-fsharp/issues/839#issuecomment-395054266 for now.

But you need to remove storage: none for the netcorebuild
This is needed otherwise people under OSX will have the intellisense problem.

[csmager]

I did a grep of the mono folder and got two hits:

/Library/Frameworks/Mono.framework/Versions/Current/lib/mono/4.5/Facades/netstandard.dll
/Library/Frameworks/Mono.framework/Versions/Current/lib/mono/4.7.1-api/Facades/netstandard.dll

Rider told me it couldn't find netstandard, but helpfully it showed me where it was searching: in lib/mono/4.5.

This seems to work for me:

#if !FAKE
  #r "Facades/netstandard"
#endif

Is there anything defined for mono so we can get something that works for both?

[matthid]

I guess someone should file a mono bug ;)

[vastcloud]

With FAKE 5.10.1,

#if !FAKE
  #r "Facades/netstandard"
#endif

is the one that works for me, too. Fortunately, that's the one that's set up in the MiniScaffold for library projects, too.

[robertpi]

I'm seeing this issue with all the suggested work rounds in place:
OS: Windows
Ionide 4.8.1
f#: Microsoft (R) F# Compiler version 10.7.0.0 for F# 4.7
dotnet sdk: 3.1.100

The header of my file looks like:

#r "paket: groupref build //"
#load "./.fake/build.fsx/intellisense.fsx"

#if !FAKE
#r "netstandard"
#r "Facades/netstandard" // https://github.com/ionide/ionide-vscode-fsharp/issues/839#issuecomment-396296095
#endif

The error message I get is:

A reference to the type 'System.String' in assembly 'netstandard' was found, but the type could not be found in that assembly F# Compiler(1109)

I also get a warning on the first line of the file:

The package management feature requires language version 5.0 use /langversion:preview F# Compiler(3302)

Not sure if this is related.