Bug: No overload for method 'this' takes 2 arguments

[seltzdesign]

Getting an error message when opening our patch in the latest Version (2021.4.2):

System.AggregateException: One or more errors occurred. ---> VL.Lang.Platforms.Roslyn.EmitException: C:\Users\seltz\Desktop\SpaceMusic\SpaceMusic\SpaceMusic_UI.vl.cs(11584,25): error CS1501: No overload for method 'this' takes 2 arguments
   at VL.Lang.Platforms.Roslyn.TargetCompilation.<>c__DisplayClass45_0.<Emit>g__EmitRelease|1()
   at VL.Lang.Platforms.Roslyn.TargetCompilation.Emit(IProjectSymbol project, CSharpCompilation compilation, Boolean isDebug, Boolean includeSource, CancellationToken token)
   at VL.Lang.Platforms.Roslyn.TargetCompilation.<>c__DisplayClass2_0.<InitializeAsync>g__Build|2(ProjectBuildRequest projectBuildRequest)
   at VL.Lang.Platforms.Roslyn.TargetCompilation.<>c__DisplayClass2_0.<InitializeAsync>g__BuildOrLoad|1(ProjectBuildRequest buildRequest)
   at VL.Lang.Platforms.Roslyn.TargetCompilation.<>c__DisplayClass2_1.<<InitializeAsync>b__5>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at VL.Lang.Platforms.Roslyn.TargetCompilation.<InitializeAsync>d__2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at VL.Lang.Platforms.Roslyn.TargetCompilation.<CreateAsync>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at VL.Lang.Platforms.Roslyn.TargetCompilation.<WithCompilationAsync>d__41.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at VL.Lang.Platforms.Roslyn.TargetCompilation.<VL-Lang-Symbols-ITargetCompilation-WithCompilationAsync>d__42.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at VL.Model.VLSession.<CreateTargetCompilationAsync>d__168.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at VL.Model.VLSession.<UpdateRuntimesAsync>d__167.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at VL.Model.VLSession.<UpdateCompilationAsync>d__187.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at VL.Model.VLSession.<UpdateCompilationAsync>d__187.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at VL.Model.VLSession.<UpdateCompilationAsync>d__184.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at VL.Model.VLSession.<UpdateAsync>d__180.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at VL.HDE.PatchEditor.NavigationMenuProvider.<DoOpenDocumentsAsync>d__47.MoveNext()
   --- End of inner exception stack trace ---
   at VL.HDE.PatchEditor.NavigationMenuProvider.<DoOpenDocumentsAsync>d__47.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at VL.Model.VLSession.<>c__DisplayClass181_0.<<RunAndForget>b__0>d.MoveNext()

Opening it in an earlier version does not cause this bug. The error is shown during loading of the file.

[Elias]

Do you know the last version in which it worked? But in any case, I fear you’ll have to send us the patch/project to get at the bottom of this.

[tonfilm]

I was able to find the util operation that has this error, it seems to be an accumulator of type Dictionary.Builder if this accumulator is replaced by a Dictionary, it compiles:
Method args bug.vl (16.9 KB)

[Elias]

Thanks, that helped! Added the patch to our unit tests.