[RFC FS-1108] Undentation frenzy

[Happypig375]

RFC: https://github.com/fsharp/fslang-design/blob/main/preview/FS-1108-undentation-frenzy.md
Suggestions:

• Allow undentation for constructors
• Relax indentation rules on mutually recursive functions when using with CE
• Relax some of the indentation rules
• Add new undentation rule for match with
• Relax indentation rules on anonymous records
• Allow undentation in method and constructor calls
• Alignment requirements for mutually recursive functions are non-intuitive
• Mutual Recursion with Async Workflow Possible Compiler Issue
• Composed function leads to unexpected indentation warning
• Warning only when function application is inside SynExpr.IfThenElse

Pull request: dotnet/fsharp#11772

[charlesroddie]

This RFC made the consistency adjustment:

type A(x:string) = class end

let x = [ // This was OK before this RFC and seemed a reasonable way to format code
    "data"
    ]

let y = A( // adjusted by this RFC for consistency, also seems reasonable
    "data"
    )

There is a side effect that the following code is allowed:

let x' =
    [ // this bracket begins on a line with only whitespace before; can we be strict in this case and not permit subsequent undentations
    "data" // this line should be required to be indented further
    ]

let y' = // similarly
    A(
    "data"
    )

The rule could be that undentations in lines following unclosed brackets/constructors are allowed when the opening bracket is of the form let _ = [opening bracket/constructor].

Thoughts @Happypig375 @dsyme ?

[dsyme]

It is a little odd that is accepted, though it was also accepted in F# 5.0 it seems

[dsyme]

That is, the first (x') was accepted without warning in F# 5.0, the second wasn't.

[charlesroddie]

Does this require a new language suggestion to fix?