Trivia before elif generates invalid code due to missing indentation

[smoothdeveloper]

Issue created from fantomas-ui

Code

let a ex =
    if null = ex then
        None
        
    elif ex.GetType() = typeof<obj> then
        Some ex
    else
        None

Error

let a ex =
    if null = ex then None
    elif

    ex.GetType() = typeof<obj> then Some ex
    else None

Options

Fantomas Next - 3.0.0-10/19/2019

Name	Value
IndentOnTryWith	false
IndentSpaceNum	4
KeepNewlineAfter	true
PageWidth	120
ReorderOpenDeclaration	false
SemicolonAtEndOfLine	false
SpaceAfterComma	true
SpaceAfterSemicolon	true
SpaceAroundDelimiter	true
SpaceBeforeArgument	true
SpaceBeforeColon	false
StrictMode	false

More information

Trivia surounding if/elif/else constructs tend to mess with indentation of the condition expression, the initial fix would be to prepend that condition with one indentation level.

A larger problem is that location of trivia such as comments or even empty lines may vary depending styles, but Fantomas seems to take the trivii and put them inside the node.

See:
sample with comments at many places