Formatting crashes on C# assembly with event

[Vidarls]

The following c# code crashes Fsharp.formatting:

I believe @matthid mentioned some issues with events during his work on improving C# support earlier..

/// <summary>
/// Event triggered when WorklistText is required
/// </summary>
[ComVisible(false)]
public delegate void WorklistTextRequested(int medicalRecordId, string accessionNo, 
  int templateId, string specificationCode, string specificationText, string aeTitle);

public event WorklistTextRequested OnWorklistTextRequested;

Error:

Microsoft.FSharp.Compiler.ErrorLogger+ReportedError: The event 'OnWorklistTextRequested' has a non-standard type. If this event is declared in another CLI language, you may need to access this event using the explicit add_OnWorklistTextRequested and remove_OnWorklistTextRequested methods for the event. If this event is declared in F#, make the type of the event an instantiation of either 'IDelegateEvent<>' or 'IEvent<,_>'.

stack trace:

ved Microsoft.FSharp.Compiler.ErrorLogger.ErrorLoggerExtensions.ErrorLogger.Error[b](ErrorLogger x, Exception exn) i C:\GitHub\fsharp\FSharp.Compiler.Service\src\fsharp\ErrorLogger.fs:linje 321
   ved Microsoft.FSharp.Compiler.Infos.ArgsTypOfEventInfo(InfoReader infoReader, range m, AccessorDomain ad, EventInfo einfo) i C:\GitHub\fsharp\FSharp.Compiler.Service\src\fsharp\infos.fs:linje 3805
   ved Microsoft.FSharp.Compiler.Infos.PropTypOfEventInfo(InfoReader infoReader, range m, AccessorDomain ad, EventInfo einfo) i C:\GitHub\fsharp\FSharp.Compiler.Service\src\fsharp\infos.fs:linje 3816
   ved Microsoft.FSharp.Compiler.SourceCodeServices.FSharpMemberOrFunctionOrValue.get_ReturnParameter() i C:\GitHub\fsharp\FSharp.Compiler.Service\src\fsharp\vs\Symbols.fs:linje 1441
   ved FSharp.MetadataFormat.ValueReader.readMemberOrVal(ReadingContext ctx, FSharpMemberOrFunctionOrValue v) i c:\Tomas\Public\FSharp.Formatting\src\FSharp.MetadataFormat\Main.fs:linje 343
   ved [email protected](String cat, IDictionary`2 _arg1, Comment comment) i c:\Tomas\Public\FSharp.Formatting\src\FSharp.MetadataFormat\Main.fs:linje 778
   ved FSharp.MetadataFormat.Reader.readCommentsInto[a](ReadingContext ctx, String xmlDoc, FSharpFunc`2 f) i c:\Tomas\Public\FSharp.Formatting\src\FSharp.MetadataFormat\Main.fs:linje 763
   ved FSharp.MetadataFormat.Reader.tryReadMember(ReadingContext ctx, MemberKind kind, FSharpMemberOrFunctionOrValue memb) i c:\Tomas\Public\FSharp.Formatting\src\FSharp.MetadataFormat\Main.fs:linje 777
   ved [email protected](FSharpMemberOrFunctionOrValue memb) i c:\Tomas\Public\FSharp.Formatting\src\FSharp.MetadataFormat\Main.fs:linje 784
   ved Microsoft.FSharp.Collections.IEnumerator.choose@163.System-Collections-IEnumerator-MoveNext()
   ved Microsoft.FSharp.Collections.SeqModule.ToList[T](IEnumerable`1 source)
   ved [email protected](String cat, IDictionary`2 cmds, Comment comment) i c:\Tomas\Public\FSharp.Formatting\src\FSharp.MetadataFormat\Main.fs:linje 896
   ved FSharp.MetadataFormat.Reader.readCommentsInto[a](ReadingContext ctx, String xmlDoc, FSharpFunc`2 f) i c:\Tomas\Public\FSharp.Formatting\src\FSharp.MetadataFormat\Main.fs:linje 763
   ved FSharp.MetadataFormat.Reader.readType(ReadingContext ctx, FSharpEntity typ) i c:\Tomas\Public\FSharp.Formatting\src\FSharp.MetadataFormat\Main.fs:linje 858
   ved [email protected](ReadingContext ctx, FSharpEntity typ) i c:\Tomas\Public\FSharp.Formatting\src\FSharp.MetadataFormat\Main.fs:linje 851
   ved Microsoft.FSharp.Collections.IEnumerator.choose@163.System-Collections-IEnumerator-MoveNext()
   ved Microsoft.FSharp.Collections.SeqModule.ToList[T](IEnumerable`1 source)
   ved FSharp.MetadataFormat.Reader.readModulesAndTypes(ReadingContext ctx, IEnumerable`1 entities) i c:\Tomas\Public\FSharp.Formatting\src\FSharp.MetadataFormat\Main.fs:linje 852
   ved FSharp.MetadataFormat.Reader.readNamespace(ReadingContext ctx, String ns, IEnumerable`1 entities) i c:\Tomas\Public\FSharp.Formatting\src\FSharp.MetadataFormat\Main.fs:linje 930
   ved [email protected](Tuple`2 tupledArg) i c:\Tomas\Public\FSharp.Formatting\src\FSharp.MetadataFormat\Main.fs:linje 955
   ved [email protected](b& )
   ved Microsoft.FSharp.Collections.IEnumerator.MapEnumerator`1.System-Collections-IEnumerator-MoveNext()
   ved Microsoft.FSharp.Collections.SeqModule.ToList[T](IEnumerable`1 source)
   ved FSharp.MetadataFormat.Reader.readAssembly(FSharpAssembly assembly, Boolean publicOnly, String xmlFile, FSharpOption`1 sourceFolderRepo, FSharpFunc`2 urlRangeHighlight, Boolean markDownComments, IUrlHolder urlMap) i c:\Tomas\Public\FSharp.Formatting\src\FSharp.MetadataFormat\Main.fs:linje 958
   ved <StartupCode$FSharp-MetadataFormat>[email protected](IEnumerable`1& next) i c:\Tomas\Public\FSharp.Formatting\src\FSharp.MetadataFormat\Main.fs:linje 0
   ved Microsoft.FSharp.Core.CompilerServices.GeneratedSequenceBase`1.MoveNextImpl()
   ved Microsoft.FSharp.Core.CompilerServices.GeneratedSequenceBase`1.System-Collections-IEnumerator-MoveNext()
   ved Microsoft.FSharp.Collections.SeqModule.ToList[T](IEnumerable`1 source)
   ved FSharp.MetadataFormat.MetadataFormat.Generate(FSharpList`1 dllFiles, String outDir, IEnumerable`1 layoutRoots, FSharpOption`1 parameters, FSharpOption`1 namespaceTemplate, FSharpOption`1 moduleTemplate, FSharpOption`1 typeTemplate, FSharpOption`1 xmlFile, FSharpOption`1 sourceRepo, FSharpOption`1 sourceFolder, FSharpOption`1 publicOnly, FSharpOption`1 libDirs, FSharpOption`1 otherFlags, FSharpOption`1 markDownComments, FSharpOption`1 urlRangeHighlight, FSharpOption`1 assemblyReferences) i c:\Tomas\Public\FSharp.Formatting\src\FSharp.MetadataFormat\Main.fs:linje 1084

[matthid]

I never saw this (maybe because I don't do much C# with events). For one-time events I use task (which is safer in multi thread environments) and IObservable otherwise.

For the exception: This looks like a FCS bug/limitation (I have a FCS only repro here).
@dsyme Why are we not allowed to call ReturnParameter on C# events? Should we work around that or open an issue on FCS?

[Vidarls]

This particular case is COM (vb6) -> .net interop and as such I have to use events,

[matthid]

In this case I don't see any "quick" fix, you can try to work around this in F# Formatting by checking for an event and don't calling the ReturnParameter property. Or try to do the proper fix in FCS if dsyme agrees that this is a bug (I have linked the testcase above).

[matthid]

The problem was mentioned here before: #208 (comment)

[matthid]

As a workaround: Adding [omit] works.

/// <summary>
/// [omit]
/// </summary>

[matthid]

Alternatively you can try to use 2.11.0-alpha2 which has improved error handling and can recover from this. Can you report this to FCS to fix the root issue? FSF will still print out the error message and the event will be missing from the generated documentation.

[Vidarls]

Thanks, I'm trying my luck with FCS.

Do you know of any known issues in the alpha releases of FSF, or should I not expect much trouble updating?

[matthid]

There are no known issues. Its just a quick way for me to make and test a release even before @tpetricek had some time to review, comment or discuss the changes.

[dsyme]

See comment about events here: #208 (comment)

[matthid]

I think this can be closed now.