Warning only when function application is inside SynExpr.IfThenElse

[nojaf]

Consider the following code example:

let a =
  System.Text.RegularExpressions.Regex.IsMatch(
    "myInput",
    """^[a-zA-Z][a-zA-Z0-9']+$"""
   )

if System.Text.RegularExpressions.Regex.IsMatch(
    "myInput",
    """^[a-zA-Z][a-zA-Z0-9']+$"""
   ) then
  ()

I get an indentation warning when the function call is inside the if condition.
But not when it is used in a let binding body.

Expected behavior

I would expect both cases not to show any warnings.

Actual behavior

Warning for the expression inside the if/then/else

Known workarounds

Wrap the if condition inside parenthesises.

if (System.Text.RegularExpressions.Regex.IsMatch(
     "myInput",
      """^[a-zA-Z][a-zA-Z0-9']+$"""
   )) then
  ()

Related information

Provide any related information (optional):

• Operating system: Win 10
• .NET Runtime kind (.NET Core, .NET Framework, Mono): .NET 5
• Editing Tools (e.g. Visual Studio Version, Visual Studio): FCS 38.0.0

Related Fantomas bug: fsprojects/fantomas#1349

[cartermp]

Other workaround :)

if System.Text.RegularExpressions.Regex.IsMatch(
                                                "myInput",
                                                """^[a-zA-Z][a-zA-Z0-9']+$"""
                                               ) then
  ()

I know that @dsyme has preferred these to be tracked as RFCs for some reason but it just kinda feels like a bug to me at this point.

[nojaf]

Yeah, then the next lad complains that the max line length is not respected 🙃.
I can't win in these situations 😋.

Anyway, Don if this needs an RFC, please let me know.

[nojaf]

This also happens in match expressions.
For example:

let b ="True"
let foo () =
    match Boolean.TryParse (
            b
          ) with
    | true, i -> Some i
    | false, _ -> failwith ""

@cartermp, @dsyme how do you want to see this fixed? If it should be fixed at all of course.

[dsyme]

This relaxation should be tracked by a language suggestion, which we can consdier approved-in-principle.

[dsyme]

Fixed in preview #11772