Latest fantomas breaks Falanx indentation

[7sharp9]

Description

The latest 2.9.1 has incorrect indentation

Repro code

See https://github.com/jet/falanx/issues/84

[nojaf]

Hi @7sharp9, could you give us some more pointers how to solve this. The F# code in https://github.com/jet/falanx/issues/84 is coming from where? Would it be possible to have a smaller reproduction in the online tool?

[jindraivanek]

I think main culprit here is let ... in ... support (https://github.com/fsprojects/fantomas/blob/c5597b7c1b63466a01dea7c6fed750bade9b5f49/src/Fantomas/CodePrinter.fs#L665).

• It doesn't work correctly for multiline expr after in - it tries to output it like this

  let x = 1 in ()
           x

  which is not valid

• in shoudln't be used at all when generating from AST (I guess it is used because all nodes have same zero range).

I will try to fix it by disabling let ... in for multiline and when generating from AST.