The solution provided here is originally from Harry Stonelicker. This issue is decribed here https://github.com/Microsoft/visualfsharp/issues/4574
possible solutions to VS2017 sluggish behavior are unchecking following features in Text Editor > F# > Code Fixes / Performance
According to https://blogs.msdn.microsoft.com/dotnet/2018/04/18/visual-studio-2017-15-7-preview-4/ the new 15.7 Preview 4 should be faster. I'll try it and see if that's true...
Visual Studio 2019 is faster - they also seemed to have fixed the intellisense memory leak.
Consider looking into alternative IDEs:
- Jetbrains Rider for .net framework and non-media solutions (they don't yet support .net core for F#, there are also problems with the diffGenerator)
- VS Code for .net core or standard solutions, tooling is provided by the
ionide-fsharp
extension