Improve internal type signature

[fxdmhtt]

The signature of GroupBy.Invoke function is abnormal, which causes the secondary encapsulated 'Collection<'T> type to be incorrectly identified (identified as Id<'T>).

Refer to ChunkBy.Invoke, this should be just a typo.

[wallymathieu]

Note the ticks in the type signature. The C here is more for documentation rather than an actual type

[gusty]

Yes, it won't change any behavior. Not even a public signature.
But it reads better, so we can accept the PR as a code readability improvement.

[wallymathieu]

For sure, I’m wondering if @fxdmhtt has some issue with code? Something that does not compile?

[gusty]

The signature of GroupBy.Invoke function is abnormal, which causes the secondary encapsulated 'Collection<'T> type to be incorrectly identified (identified as Id<'T>).

@fxdmhtt please create an issue for this. with a small repro, then we can help and reference eventually a PR that will address it.

We'll accept this PR but it's unlikely that it will solve any issue.

[fxdmhtt]

I have seen your reply and I completely agree with what you said.

I think it is more of my own problem and I didn't want to bother you about it.

Please allow me to extract a minimal reproducible code tomorrow. Thank you very much!

[fxdmhtt]

Thank you very much.

The minimal example code is as follows:

open FSharpPlus

let inline groupby (key: 'T -> 'Key when 'Key : equality) (sequence: '``Collection<'T>``) : Map<'Key, '``Collection<'T>``> =
    sequence
    |> groupBy key
    |> Map.ofSeq

I will get a wavy line error on groupBy:

The type 'Internals.Id<'Key * Internals.Id<'T>>' is not compatible with the type '('Key * 'Collection<'T>) seq'.

This code doesn't really mean anything, I'm just more familiar with Python so I'm trying to simulate the behavior of the Toolz package. This is a toy.

Specifically, I'm trying to wrap the generic groupBy as Toolz.groupby

I'm a beginner in F# and don't know if this problem is caused by FSharpPlus, but as of now, I really don't have any idea to solve this compilation error.

FSharpPlus: 1.7.0
OS: Windows 10
.NET: 9.0

Thanks again!

Additional information:

I found that when the function signature is changed to the following:

let inline groupby (key: 'T -> 'Key when 'Key : equality) (sequence: '``Collection<'T>``) =
    sequence
    |> groupBy key
    |> Map.ofSeq

that is, the signature of the function output is removed.

the compilation error will disappear, but the type inference will not be able to recognize the real information.

The Ionide plugin infers:

val inline groupby:
   key     : ('T -> 'Key) ->
   sequence: 'Collection<'T> (requires static member GroupBy )
          -> Map<'b,'c> (requires comparison)

I don't know how to modify