Error in formatting nested else if construction

[nojaf]

Issue created from fantomas-ui

Please describe here fantomas problem you encountered

Code

namespace Fantomas

module String =
    let merge a b =
            if la <> lb then 
                if la > lb then a' else b'
            else
                if String.length a' < String.length b' then a' else b' 

Error

Exception: Unexpected scenario when formatting else if / elif, please open an issue via https://jindraivanek.gitlab.io/fantomas-ui Stack Trace:    at Fantomas.TriviaContext.else if / elif(range rangeOfIfThenElse, Context ctx)
   at Fantomas.CodePrinter.genElifOneliner@1211-2.Invoke(Context x)
   at Fantomas.CodePrinter.genElifOneliner@1211-3.Invoke(Context x)
   at Fantomas.CodePrinter.genElifOneliner@1212-5.Invoke(Context x)
   at Fantomas.CodePrinter.genElifOneliner@1213-6.Invoke(Context x)
   at Fantomas.CodePrinter.genElifOneliner@1214-8.Invoke(Context x)
   at Fantomas.CodePrinter.genElifOneliner@1215-9.Invoke(Context x)
   at Fantomas.CodePrinter.genTrivia@2268-1.Invoke(Context x)
   at Fantomas.Context.col[T](FSharpFunc`2 f', IEnumerable`1 c, FSharpFunc`2 f, Context ctx)
   at Fantomas.Context.colPost[T](FSharpFunc`2 f2, FSharpFunc`2 f1, IEnumerable`1 c, FSharpFunc`2 f, Context ctx)
   at Fantomas.CodePrinter.genExpr@1324-324.Invoke(Context x)
   at Fantomas.Context.atIndentLevel@176-6.Invoke(Context x)
   at Fantomas.Context.atIndentLevel(Boolean alsoSetIndent, Int32 level, FSharpFunc`2 f, Context ctx)
   at Fantomas.CodePrinter.genTrivia@2268-1.Invoke(Context x)
   at Fantomas.Context.futureNlnCheckMem@412-1.Invoke(Tuple`2 tupledArg)
   at System.Lazy`1.ViaFactory(LazyThreadSafetyMode mode)
   at System.Lazy`1.ExecutionAndPublication(LazyHelper executionAndPublication, Boolean useDefaultConstructor)
   at System.Lazy`1.CreateValue()
   at Fantomas.Cache.memoizeBy@91.Invoke(a x)
   at Fantomas.Context.futureNlnCheck(FSharpFunc`2 f, Context ctx)
   at Fantomas.CodePrinter.genExprSepEqPrependType(ASTContext astContext, FSharpFunc`2 prefix, SynPat pat, SynExpr e, Context ctx)
   at Fantomas.CodePrinter.genTrivia@2268-1.Invoke(Context x)
   at Fantomas.CodePrinter.genTrivia@2268-1.Invoke(Context x)
   at Fantomas.CodePrinter.genModuleDecl@331-46.Invoke(Context x)
   at Fantomas.CodePrinter.genTrivia@2268-1.Invoke(Context x)
   at Fantomas.CodePrinter.genTrivia@2268-1.Invoke(Context x)
   at Fantomas.Context.col[T](FSharpFunc`2 f', IEnumerable`1 c, FSharpFunc`2 f, Context ctx)
   at Fantomas.CodePrinter.genImpFile@79-6.Invoke(Context ctx)
   at Fantomas.CodeFormatterImpl.formatWith(ParsedInput ast, FSharpList`1 defines, FormatContext formatContext, FormatConfig config)
   at Fantomas.CodeFormatterImpl.format@406-1.Invoke(Tuple`2[] _arg1)
   at Microsoft.FSharp.Control.AsyncPrimitives.CallThenInvokeNoHijackCheck[a,b](AsyncActivation`1 ctxt, FSharpFunc`2 userCode, b result1) in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 416
   at Microsoft.FSharp.Control.Trampoline.Execute(FSharpFunc`2 firstAction) in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 109
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.FSharp.Control.AsyncResult`1.Commit() in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 349
   at Microsoft.FSharp.Control.AsyncPrimitives.RunSynchronouslyInCurrentThread[a](CancellationToken cancellationToken, FSharpAsync`1 computation) in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 870
   at Microsoft.FSharp.Control.AsyncPrimitives.RunSynchronously[T](CancellationToken cancellationToken, FSharpAsync`1 computation, FSharpOption`1 timeout) in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 890
   at Microsoft.FSharp.Control.FSharpAsync.RunSynchronously[T](FSharpAsync`1 computation, FSharpOption`1 timeout, FSharpOption`1 cancellationToken) in E:\A\_work\130\s\src\fsharp\FSharp.Core\async.fs:line 1153
   at Server.Result.attempt[a](FSharpFunc`2 f) in /build/src/Server/Server.fs:line 24

Options

Fantomas 3.1.0

Name	Value
IndentOnTryWith	false
IndentSpaceNum	4
KeepNewlineAfter	false
MaxIfThenElseShortWidth	40
PageWidth	120
ReorderOpenDeclaration	false
SemicolonAtEndOfLine	false
SpaceAfterComma	true
SpaceAfterSemicolon	true
SpaceAroundDelimiter	true
SpaceBeforeArgument	true
SpaceBeforeColon	false
StrictMode	false