[RFC FS-1046] Wildcard self identifier. Allow single underscore in members.

[gusty]

This allows writing a single underscore in member definitions, ie member _.DoSomething().

[dnfclas]

All CLA requirements met.

[cartermp]

@gusty is there a language suggestion change that maps to this? Generally I'm in favor.

Another interesting one (if you're digging around in there) is for __ in do:

Error message kinda sucks, and the resolution is a double _.

[gusty]

Yes, it's approved in principle, see fsharp/fslang-suggestions#333

I've never thought about the for _ in, I will dig into it, in a separate PR.

[cartermp]

@gusty Thanks!

[matthid]

Thanks a lot for trying to take care of this wart ;)

[cartermp]

Note: this code fixer can also be changed with this PR: https://github.com/dotnet/fsharp/blob/master/vsintegration/src/FSharp.Editor/CodeFix/RenameUnusedValue.fs#L73

[gusty]

Actually for the renamer you suggested it won't cause problems. I was thinking in the warning mechanisms. For the identifiers starting with underscore it won't be a problem, but for existing member x. we could issue a warning once this feature is added, but as I said it would be sort of a breaking change.

I had a look at how it works right now and it already considers unused bindings everything that doesn't start with an underscore, so we're good to change the renamer too.

[gusty]

@cartermp I adjusted the renamer, as you suggested.

[KevinRansom]

targeting fsharp47

[KevinRansom]

Nice,

thx

[cartermp]

Love it, thanks a lot @gusty

[pauldorehill]

Love this update, however I noticed that it doesn't work with an accessibility modifier:

type MyType =
    { Hello : string }
    member private __.WorldOk = "World ok"
    member private _.WorldOhNo = "World not ok"

Do you want me to open a separate issue?

[gusty]

Good catch !

I've just added a PR (#7631) that will cover that case.