Can't format fragment of source code with #if element, and keyword, and triple-slash comment

[knocte]

Issue created from fantomas-online

Code

module Primitives =
    type BlockHeight =
        | BlockHeight of uint32 

    /// **Description**
    ///
    /// 16bit relative block height used for `OP_CSV` locks,
    /// Since OP_CSV allow only block number of 0 ~ 65535, it is safe
    /// to restrict into the range smaller than BlockHeight
    and
#if !NoDUsAsStructs
        [<Struct>]
#endif
        BlockHeightOffset16 =
            | BlockHeightOffset16 of uint16

Error

Fantomas.Core.FormatConfig+FormatException: Fantomas is trying to format the input multiple times due to the detect of multiple defines.
There is a problem with merging all the code back together.
[] has 2 fragments
[NoDUsAsStructs] has 3 fragments
Please raise an issue at https://fsprojects.github.io/fantomas-tools/#/fantomas/preview.
   at Fantomas.Core.CodeFormatterImpl.format@87-5.Invoke(FSharpList`1 results) in /_//src/Fantomas.Core/CodeFormatterImpl.fs:line 108
   at Microsoft.FSharp.Control.AsyncPrimitives.CallThenInvokeNoHijackCheck[a,b](AsyncActivation`1 ctxt, b result1, FSharpFunc`2 userCode) in D:\a\_work\1\s\src\fsharp\FSharp.Core\async.fs:line 465
   at Microsoft.FSharp.Control.Trampoline.Execute(FSharpFunc`2 firstAction) in D:\a\_work\1\s\src\fsharp\FSharp.Core\async.fs:line 104

Problem description

Please describe here the Fantomas problem you encountered.
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Extra information

• The formatted result breaks my code.
• The formatted result gives compiler warnings.
• I or my company would be willing to help fix this.

Options

Fantomas master branch at 2022-07-11T16:44:40Z - 98a7449

Default Fantomas configuration

_{Did you know that you can ignore files when formatting from fantomas-tool or the FAKE targets by using a .fantomasignore file?}

[nojaf]

This indeed is a bug, the problem is that the trivia between and and the [<Struct>] isn't being restored correctly. This can be better spotted when changing it to a comment.

In order to solve this Fantomas needs to know about the and keyword in the AST.
This should be added to the SynTypeDefnTrivia over at dotnet/fsharp.

I can provide some pointers if anybody want to contribute this to the F# compiler.

[nojaf]

Fix available in v5.2.0-beta-001