Unnecessary conversion from 'YieldOrReturn' to 'YieldOrReturnFrom'

[zakaluka]

Per @jindraivanek's request, I am splitting off the second issue from #315.

Second question is about when I format through the Fantomas library and FAKE. I am seeing the following error message when I try to run the Server.fs file through checkCode.

D:\projects\ZenCase\src\Client\Client.fs:
Unable to cast object of type 'YieldOrReturn' to type 'YieldOrReturnFrom'.

D:\projects\ZenCase\src\Server\Server.fs:
Unable to cast object of type 'YieldOrReturn' to type 'YieldOrReturnFrom'.

The following files aren't formatted properly:
- D:\projects\ZenCase\src\Client\AssemblyInfo.fs
- D:\projects\ZenCase\src\Client\Client.fs !
- D:\projects\ZenCase\src\Migration\AssemblyInfo.fs
- D:\projects\ZenCase\src\Migration\Constants.fs
- D:\projects\ZenCase\src\Migration\Migration.fs
- D:\projects\ZenCase\src\Server\AssemblyInfo.fs
- D:\projects\ZenCase\src\Server\Server.fs !
- D:\projects\ZenCase\src\Shared\Shared.fs
- D:\projects\ZenCase\src\Shared\Utility.fs)

If I comment out all the computation expressions in Server.fs, then that error goes away. However, any computation express in Server.fs causes the error to be printed out. Because of this, I'm concerned about running Server.fs through formatCode.

I even tried leaving only one computation expression Server.fs:

let getInitCounter() : Task<Counter> = task { return 42 }

Based on what I saw in Fantomas, this is a YieldOrReturn. I still get the same error message. Why is Fantomas trying to change this to YieldOrReturnFrom (aka return!)?

---

@jindraivanek confirmed some additional details:

1. I can confirm this, @zakaluka please create seperate issue with this snippet. It doesn't happen for each CE, my guess is it is connected to multiline expr as first thing in CE.
2. Also confirmed. It can be reproduced wtih this FAKE5 script:

#r "paket: nuget Fantomas"
#load ".fake/test-FAKE5.fsx/intellisense.fsx"

let mkTempFile source =
    let fileName = System.IO.Path.GetTempFileName() + ".fs"
    System.IO.File.WriteAllText(fileName, source)
    fileName

let source = "let getInitCounter() : Task<Counter= task { return 42 }"

let path = mkTempFile source

Fantomas.CodeFormatter.FormatDocument(path, System.IO.File.ReadAllText(path), Fantomas.FormatConfig.FormatConfig.Default)

System.IO.File.Delete path

It's weird because with CLI this code will be formatted without problem.

[zakaluka]

From the investigation, it appears that a mismatch in FSharp.Compiler.Service versions is to blame.

[jindraivanek]

Thanks @zakaluka. I reiterate here:

I think we have two options how to fix this:

1. upgrade FSharp.Compiler.Service to 25.0.1. That will force everyone who is using Fantomas as lib to also upgrade. Not sure if that is OK.
2. change FSharp.Compiler.Service dependency in nuget to be exactly 23.0.3 (now is >=23.0.3). That would probably needs to change way of how we are creating nuget package, I wasn't able to find a way how to do it by dotnet pack parameter. It should be doable with paket pack.

I would prefer option 1.

@7sharp9, @auduchinok do you see any problem with Fantomas upgade to FSharp.Compiler.Service 25.0.1?

[auduchinok]

@jindraivanek No, no problem at all on our side.
We have to repack both FCS and Fantomas so they reference the same FSharp.Core we ship anyways. We build Fantomas against our FCS fork that's updated from time to time.

[nojaf]

@zakaluka the new release is out, could you confirm the problem is solved and close the issue if so?

[zakaluka]

@nojaf I am traveling for the next few weeks, but will try to test this as soon as I am able. Unfortunately, the code I was testing on is on a desktop I do not currently have access to. I will see if I can just create a new project and test the results there.

[nojaf]

Hi @zakaluka, no worries. Life happens. Thanks for replying and following this up.

[zakaluka]

@nojaf I've confirmed that the issue is not occurring any longer. Closing.