Override ToString for discriminated unions and records

[baronfel]

Submitted by Vasily Kirichenko on 4/15/2015 12:00:00 AM
181 votes on UserVoice prior to migration

It's a pain and dirty to add override x.ToString() = sprintf "%A" x to every type in order to make String.Format() happy:

type T1 =
  { Id: int
    Version: string }
override x.ToString() = sprintf "%A" x

type DU =
| C1 of int
| C2
override x.ToString() = sprintf "%A" x

I think it's very easy to teach the compiler generate this override automatically for all user types.

Response

** by fslang-admin on 6/23/2016 12:00:00 AM **

Marking as planned, though we need to work out the details
Don Syme
F# Language and Core Library Evolution

Original UserVoice Submission

[kurtschelfthout]

RFC was added.

[dsyme]

@kurtschelfthout I've added you as write-admin in this repo if you want to edit issue descriptions directly, thanks

[kurtschelfthout]

@dsyme, will do. Thanks!

[dsyme]

This is now covered by the RFC and has already been implemented. Thanks all!

[Porges]

Question from the sky: Is this implemented in such a way that it avoids the performance penalties of sprintf "%A"? (ie. is ToString a generated equivalent of the result of sprintf "%A", or does it just call it)

[abelbraaksma]

New location of RFC: https://github.com/fsharp/fslang-design/blob/main/FSharp-4.1b/FS-1022-override-ToString-for-discriminated-unions-and-records.md.

This was implemented for F# 4.1.

[abelbraaksma]

@Porges see here for more info: #919