Formatting if expressions can have problems when applying the short syntax style.

[nojaf]

Hello,

I believe I found a weakness in the rule:

If either cond, e1 or e2 are longer, but not multi-line:

if cond
then e1
else e2

if e1 is also a SynExpr.IfThenElse it can lead to a compiler error.
Related Fantomas bug: fsprojects/fantomas#1243

                        if f.IsProperty then
                            if f.IsInstanceMember then
                                if f.IsDispatchSlot then 9 else 1
                            else 8
                        elif f.IsMember then
                            if f.IsInstanceMember then
                                if f.IsDispatchSlot then 11 else 2
                            else 10
                        else 3

was transformed to

                if f.IsProperty
                then if f.IsInstanceMember then if f.IsDispatchSlot then 9 else 1 else 8
                elif f.IsMember
                then if f.IsInstanceMember then if f.IsDispatchSlot then 11 else 2 else 10
                else 3

On a personal note, I never was overly fond of the longer, but not multi-line, it leaves a lot of room for interpretation what "longer" is.
My proposal would be to remove the rule and add a further restriction to If cond, e1 and e2 are short, simply write them on one line:, that e1 or e2 cannot be an if/then/else itself.

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Document Details

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• ID: 8c09996f-24ac-cf39-ef43-d7909cbc2b89
• Version Independent ID: 1efdd523-8552-6421-e149-74f76826ef8f
• Content: F# code formatting guidelines
• Content Source: docs/fsharp/style-guide/formatting.md
• Product: dotnet-fsharp
• GitHub Login: @cartermp
• Microsoft Alias: phcart

[cartermp]

Thanks, that is good feedback. I'd be happy to accept a PR that adjusts the guidance!