FSharp Interactive won't start; can't find System.Runtime.dll

Question

I've installed FSharp 4.1 through the Visual Studio 2017 installer, but FSI refuses to start:

PS C:\Program Files (x86)\Microsoft SDKs\F#\4.1\Framework\v4.0> .\fsi

Unhandled Exception: System.IO.FileNotFoundException: Could not load file or assembly
'System.Runtime, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one
of its dependencies. The system cannot find the file specified.
   at Microsoft.FSharp.Compiler.Interactive.Shell.MainMain(String[] argv)

I assume I'm missing something in a PATH variable or something, but despite several reinstalls and repairs I can't get past this error.

Where is FSI looking for this dll, and what should I install to put it there?

Update:

I've tried a few things, with no change to the outcome:

• Remove F# 4.1 through the VS 2017 installer, verify that C:\Program Files (x86)\Microsoft SDKs\F#\4.1 did not exist, and reinstall F# 4.1
• Uninstall all versions of .NET Core I had installed
• Remove the C:\Program Files (x86)\Microsoft SDKs\F#\4.0 directory that doesn't seem to have an installer that cares for it. (FSI in that directory worked prior to removal...)

I've dumped the fusion logs to a zip file and put it on my Google Drive. There's a whole bunch of failed bindings, System.Runtime, Version 4.1.0.0 being one of them.

Issue filed here: https://github.com/Microsoft/visualfsharp/issues/3178

Answer 1

This has now been resolved over at github, but for completeness, here's a summary.

The problem was that I, for some reason, had registered FSharp.Core 4.1.0.0 in the GAC:

C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise>gacutil /l FSharp.Core
Microsoft (R) .NET Global Assembly Cache Utility.  Version 4.0.30319.0
Copyright (c) Microsoft Corporation.  All rights reserved.

The Global Assembly Cache contains the following assemblies:
  FSharp.Core, Version=2.3.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL
  FSharp.Core, Version=4.4.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL
  FSharp.Core, Version=4.4.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL

Number of items = 3

The third entry should not be there. I removed that:

gacutil /uf "FSharp.Core, Version=4.4.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL"

After that, FSI and dotnet new started working correctly. To get Visual Studio to work, I also had to repair my VS installation and reboot, and now everything works.

Answer 2

So the binary that is being executed there is the coreclr version of the compiler. And the version of the compiler that vs installs in that directory is the desktop version of the compiler.

I assume that somehow the coreclr version got copied there. To fix it I would do this: * Run vs setup, deselect Tools for F# programming.

Once VS setup has uninstalled F#.

delete the compiler directory: "C:\Program Files (x86)\Microsoft SDKs\F#\4.1"

The rerun vs setup and select the Tools for F# programming.

If it still repros after that then open an issue at https://github.com/Microsoft/visualfsharp

Thanks

Kevin