Indexer usage fails to parse

[maxdeviant]

Description

F# code that tries to use an indexer on an object fails to parse.

Here is the problematic line of code:

analysisKey.Headers.Item(key) <- value

I imagine this probably isn't a very common case 😅

Stack trace

Exception: Unexpected expression: NamedIndexedPropertySet
  (LongIdentWithDots
     ([analysisKey; Headers; Item],
      [tmp.fsx (15,19--15,20) IsSynthetic=false;
       tmp.fsx (15,27--15,28) IsSynthetic=false]),
   Paren
     (Ident key,tmp.fsx (15,32--15,33) IsSynthetic=false,
      Some tmp.fsx (15,36--15,37) IsSynthetic=false,
      tmp.fsx (15,32--15,37) IsSynthetic=false),Ident value,
   tmp.fsx (15,8--15,46) IsSynthetic=false) Stack Trace:    at Microsoft.FSharp.Core.PrintfModule.PrintFormatToStringThenFail@1637.Invoke(String message) in E:\A\_work\130\s\src\fsharp\FSharp.Core\printf.fs:line 1637
   at Fantomas.CodePrinter.genExpr(ASTContext astContext, SynExpr synExpr) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 1168
   at Fantomas.CodePrinter.noIndentBreakNln(ASTContext astContext, SynExpr e, Context ctx) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 494
   at [email protected](Context x) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 886
   at [email protected](Context x) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 2036
   at Fantomas.Context.autoNlnCheck[a](FSharpFunc`2 f, FSharpFunc`2 sep, Context ctx) in /build/.deps/fantomas/src/Fantomas/Context.fs:line 390
   at Fantomas.Context.autoNlnOrAddSep(FSharpFunc`2 f, FSharpFunc`2 sep, Context ctx) in /build/.deps/fantomas/src/Fantomas/Context.fs:line 413
   at [email protected](Context x) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 1023
   at Fantomas.Context.atIndentLevel(Boolean alsoSetIndent, Int32 level, FSharpFunc`2 f, Context ctx) in /build/.deps/fantomas/src/Fantomas/Context.fs:line 164
   at [email protected](Context ctx) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 1017
   at [email protected](Context x) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 2036
   at [email protected](Context x) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 1223
   at Fantomas.Context.atIndentLevel(Boolean alsoSetIndent, Int32 level, FSharpFunc`2 f, Context ctx) in /build/.deps/fantomas/src/Fantomas/Context.fs:line 164
   at [email protected](Context ctx) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 928
   at [email protected](Context x) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 2036
   at Fantomas.Context.col[T](FSharpFunc`2 f', IEnumerable`1 c, FSharpFunc`2 f, Context ctx) in /build/.deps/fantomas/src/Fantomas/Context.fs:line 261
   at [email protected](Context ctx) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 1068
   at Fantomas.Context.atIndentLevel(Boolean alsoSetIndent, Int32 level, FSharpFunc`2 f, Context ctx) in /build/.deps/fantomas/src/Fantomas/Context.fs:line 164
   at [email protected](Context ctx) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 1068
   at [email protected](Context x) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 2036
   at [email protected](Tuple`2 tupledArg) in /build/.deps/fantomas/src/Fantomas/Context.fs:line 397
   at System.Lazy`1.ViaFactory(LazyThreadSafetyMode mode)
   at System.Lazy`1.ExecutionAndPublication(LazyHelper executionAndPublication, Boolean useDefaultConstructor)
   at System.Lazy`1.CreateValue()
   at [email protected](a x) in /build/.deps/fantomas/src/Fantomas/Utils.fs:line 88
   at Fantomas.CodePrinter.genExprSepEqPrependType(ASTContext astContext, FSharpFunc`2 prefix, SynPat pat, SynExpr e, Context ctx) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 470
   at [email protected](Context x) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 2036
   at [email protected](Context x) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 2036
   at [email protected](Context x) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 2036
   at Fantomas.Context.col[T](FSharpFunc`2 f', IEnumerable`1 c, FSharpFunc`2 f, Context ctx) in /build/.deps/fantomas/src/Fantomas/Context.fs:line 261
   at [email protected](Context ctx) in /build/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 79
   at Fantomas.CodeFormatterImpl.formatWith(ParsedInput ast, FSharpList`1 defines, FormatContext formatContext, FormatConfig config) in /build/.deps/fantomas/src/Fantomas/CodeFormatterImpl.fs:line 390
   at [email protected](Tuple`2[] _arg1) in /build/.deps/fantomas/src/Fantomas/CodeFormatterImpl.fs:line 407
   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

Repro code

Online repro