No intellisense error or meaningful errormessage on Seq.iter build error.

[AndersBreg]

Please provide a succinct description of the issue.

Repro steps

Provide the steps required to reproduce the problem:

1. The following minimal sample doesn't get any errors from Intellisense analysis, but does not build, and with no meaningful error message.

[<EntryPoint>]
let main args =
    let doCalculation : string -> string list -> list<bool> = fun e r -> [true; false; true]
    let bestChoices =
        ["one"]
        |> Seq.map (fun context ->
            context,
            ["two"]
            |> List.ofSeq
            |> Seq.groupBy (fun choice ->
                [choice]
                |> doCalculation choice
                |> List.length
            )
            |> Seq.sortBy (fun (num, _) -> num)
        )
        |> Seq.map (fun (context, groupings) ->
            context, Seq.maxBy (fun (num, _) -> num) groupings
        )
    Seq.iter (fun (context, num, choices) ->
        List.iter (fun (num, buildings) ->
            Seq.iter (printf "%A, ") buildings
        ) choices
    ) bestChoices
    0

If possible attach a zip file with the repro case. This often makes it easier for others to reproduce.
The zip file should ideally represent the situation just before the call/step that is problematic.

Expected behavior

An intellisense message or a more detailed build error to indicate what the problem is.

Actual behavior

The build fails, with FS0001 error.

Known workarounds

Changing the outer Seq.iter to List.iter gives a correct error message both in intellisense and in the build errors.

Related information

• Windows
• .Net Core 8.0.100
• Happens both in Visual Studio and on dotnet build

[edgarfgp]

I think is similar to #17373 which is already fixed by #17516

[abonie]

Seems to have been fixed as @edgarfgp said

> [<EntryPoint>]
- let main args =
-     let doCalculation : string -> string list -> list<bool> = fun e r -> [true; false; true]
-     let bestChoices =
-         ["one"]
-         |> Seq.map (fun context ->
-             context,
-             ["two"]
-             |> List.ofSeq
-             |> Seq.groupBy (fun choice ->
-                 [choice]
-                 |> doCalculation choice
-                 |> List.length
-             )
-             |> Seq.sortBy (fun (num, _) -> num)
-         )
-         |> Seq.map (fun (context, groupings) ->
-             context, Seq.maxBy (fun (num, _) -> num) groupings
-         )
-     Seq.iter (fun (context, num, choices) ->
-         List.iter (fun (num, buildings) ->
-             Seq.iter (printf "%A, ") buildings
-         ) choices
-     ) bestChoices
-     0;;

      ) bestChoices
  ------^^^^^^^^^^^

stdin(24,7): error FS0001: The tuples have differing lengths of 3 and 2. See also stdin(24,6)-(24,17).

(that's on current main)