Wrong handling multi lines comment at the end of file after function application

[matteobaglini]

Issue created from fantomas-online

Typically comments at the end of file stay there after formatting (see test), but if the comment is a multi line one ((* . . . *) block) and the the previous line is a function application, the comment is moved between function call and parameters.

Code

printfn "Hello World"
(* This is a comment. *)

Result

printfn
(* This is a comment. *) "Hello World"

Expected Result

printfn "Hello World"
(* This is a comment. *)

Note that with a single line comment (//) it works properly.

Options

Fantomas Next - 4.0.0-alpha-001-1/1/1990

Name	Value
IndentSpaceNum	4
PageWidth	120
SemicolonAtEndOfLine	false
SpaceBeforeParameter	true
SpaceBeforeLowercaseInvocation	true
SpaceBeforeUppercaseInvocation	false
SpaceBeforeClassConstructor	false
SpaceBeforeMember	false
SpaceBeforeColon	false
SpaceAfterComma	true
SpaceBeforeSemicolon	false
SpaceAfterSemicolon	true
IndentOnTryWith	false
SpaceAroundDelimiter	true
MaxIfThenElseShortWidth	40
MaxInfixOperatorExpression	50
MaxRecordWidth	40
MaxArrayOrListWidth	40
MaxLetBindingWidth	40
MultilineBlockBracketsOnSameColumn	false
NewlineBetweenTypeDefinitionAndMembers	false
StrictMode	false

[nojaf]

Hello, this is a trivia bug. The block comment is now being assigned to the printfn Ident instead of the SynConst.String.

The problem occurs when the trivia is being assigned to a trivia node.
I think the addTriviaToTriviaNode case should be extended to support scenarios where the comment is the last line of the file.
Maybe it automatically should be assigned to the SynModule.

You can watch the first three videos on YouTube to understand how Fantomas works and what Trivia does.

I know this is a big ask, but could I persuade you to try and tackle this issue yourself?
This is a good first issue for newcomers.

[matteobaglini]

Forgive the delay response but you have definitely persuaded me 😄.

[nojaf]

Hey @matteobaglini, very cool to hear 🤗!
Many thanks for this fix!