Inline comment to the last constructor disapears

[Lev135]

(with stylish-haskell 0.14.3.0):
It happens with enums, constructor with fields and records:

data Foo
  = Foo -- ^ foo
  | Bar -- ^ bar
  | Baz -- ^ baz

data Foo'
  = Foo' Int -- ^ foo
  | Bar' Int -- ^ bar
  | Baz' Int -- ^ baz

data Foo''
  = Foo''
  { foo :: Int
  }
  -- ^ foo
  | Bar''
  { bar :: Int
  }
  -- ^ bar
  | Baz''
  { baz :: Int
  }
  -- ^ baz

after stylish:

data Foo
  = Foo -- ^ foo
  | Bar -- ^ bar
  | Baz

data Foo'
  = Foo' Int -- ^ foo
  | Bar' Int -- ^ bar
  | Baz' Int

data Foo''
  = Foo''
  { foo :: Int
  }
  -- ^ foo
  | Bar''
  { bar :: Int
  }
  -- ^ bar
  | Baz''
  { baz :: Int
  }

[Lev135]

I added a trace show in step function and I saw the following:

The reason is maybe that in GHC module structure last comment is in separate place:

data Foo
  = Foo -- ^ foo
  | Bar -- ^ bar
  | Baz -- ^ baz

L { abstract:SrcSpan }
    ( HsModule
        ( EpAnn
            ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
            ( AnnsModule ""
                ( AnnList Nothing Nothing Nothing "" "" )
            )
            ( EpaCommentsBalanced ""
                [ L
                    ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
                    ( EpaComment EpaEofComment { abstract:RealSrcSpan } )
                ]
            )
        )
        ( VirtualBraces 1 ) Nothing Nothing ""
        [ L
            ( SrcSpanAnn
                ( EpAnn
                    ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
                    ( AnnListItem "" )
                    ( EpaComments
                        [ L
                            ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
                            ( EpaComment
                                ( EpaLineComment "-- ^ baz" ) { abstract:RealSrcSpan }
                            )
                        ]
                    )
                ) { abstract:SrcSpan }
            )
            ( TyClD NoExtField
                ( DataDecl
                    ( EpAnn
                        ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
                        [ AddEpAnn AnnData
                            ( EpaSpan { abstract:RealSrcSpan } )
                        , AddEpAnn AnnEqual
                            ( EpaSpan { abstract:RealSrcSpan } )
                        ]
                        ( EpaComments
                            [ L
                                ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
                                ( EpaComment
                                    ( EpaLineComment "-- ^ bar" ) { abstract:RealSrcSpan }
                                )
                            , L
                                ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
                                ( EpaComment
                                    ( EpaLineComment "-- ^ foo" ) { abstract:RealSrcSpan }
                                )
                            ]
                        )
                    )
                    ( L
                        ( SrcSpanAnn EpAnnNotUsed { abstract:SrcSpan } )
                        ( Unqual { abstract:OccName } )
                    )
                    ( HsQTvs NoExtField "" ) Prefix
                    ( HsDataDefn NoExtField DataType Nothing Nothing Nothing
                        [ L
                            ( SrcSpanAnn
                                ( EpAnn
                                    ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
                                    ( AnnListItem
                                        [ AddVbarAnn
                                            ( EpaSpan { abstract:RealSrcSpan } )
                                        ]
                                    )
                                    ( EpaComments "" )
                                ) { abstract:SrcSpan }
                            )
                            ( ConDeclH98
                                ( EpAnn
                                    ( Anchor { abstract:RealSrcSpan } UnchangedAnchor ) ""
                                    ( EpaComments "" )
                                )
                                ( L
                                    ( SrcSpanAnn EpAnnNotUsed { abstract:SrcSpan } )
                                    ( Unqual { abstract:OccName } )
                                ) False "" Nothing
                                ( PrefixCon "" "" ) Nothing
                            )
                        , L
                            ( SrcSpanAnn
                                ( EpAnn
                                    ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
                                    ( AnnListItem
                                        [ AddVbarAnn
                                            ( EpaSpan { abstract:RealSrcSpan } )
                                        ]
                                    )
                                    ( EpaComments "" )
                                ) { abstract:SrcSpan }
                            )
                            ( ConDeclH98
                                ( EpAnn
                                    ( Anchor { abstract:RealSrcSpan } UnchangedAnchor ) ""
                                    ( EpaComments "" )
                                )
                                ( L
                                    ( SrcSpanAnn EpAnnNotUsed { abstract:SrcSpan } )
                                    ( Unqual { abstract:OccName } )
                                ) False "" Nothing
                                ( PrefixCon "" "" ) Nothing
                            )
                        , L
                            ( SrcSpanAnn EpAnnNotUsed { abstract:SrcSpan } )
                            ( ConDeclH98
                                ( EpAnn
                                    ( Anchor { abstract:RealSrcSpan } UnchangedAnchor ) ""
                                    ( EpaComments "" )
                                )
                                ( L
                                    ( SrcSpanAnn EpAnnNotUsed { abstract:SrcSpan } )
                                    ( Unqual { abstract:OccName } )
                                ) False "" Nothing
                                ( PrefixCon "" "" ) Nothing
                            )
                        ] ""
                    )
                )
            )
        ] Nothing Nothing
    )

compare with standalone comments (for wich we have correct behavior):

data Foo
  -- | foo
  = Foo
  -- | Bar
  | Bar
  -- | Baz
  | Baz

L { abstract:SrcSpan }
    ( HsModule
        ( EpAnn
            ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
            ( AnnsModule ""
                ( AnnList Nothing Nothing Nothing "" "" )
            )
            ( EpaCommentsBalanced ""
                [ L
                    ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
                    ( EpaComment EpaEofComment { abstract:RealSrcSpan } )
                ]
            )
        )
        ( VirtualBraces 1 ) Nothing Nothing ""
        [ L
            ( SrcSpanAnn
                ( EpAnn
                    ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
                    ( AnnListItem "" )
                    ( EpaComments "" )
                ) { abstract:SrcSpan }
            )
            ( TyClD NoExtField
                ( DataDecl
                    ( EpAnn
                        ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
                        [ AddEpAnn AnnData
                            ( EpaSpan { abstract:RealSrcSpan } )
                        , AddEpAnn AnnEqual
                            ( EpaSpan { abstract:RealSrcSpan } )
                        ]
                        ( EpaComments
                            [ L
                                ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
                                ( EpaComment
                                    ( EpaLineComment "-- | baz" ) { abstract:RealSrcSpan }
                                )
                            , L
                                ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
                                ( EpaComment
                                    ( EpaLineComment "-- | bar" ) { abstract:RealSrcSpan }
                                )
                            , L
                                ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
                                ( EpaComment
                                    ( EpaLineComment "-- | foo" ) { abstract:RealSrcSpan }
                                )
                            ]
                        )
                    )
                    ( L
                        ( SrcSpanAnn EpAnnNotUsed { abstract:SrcSpan } )
                        ( Unqual { abstract:OccName } )
                    )
                    ( HsQTvs NoExtField "" ) Prefix
                    ( HsDataDefn NoExtField DataType Nothing Nothing Nothing
                        [ L
                            ( SrcSpanAnn
                                ( EpAnn
                                    ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
                                    ( AnnListItem
                                        [ AddVbarAnn
                                            ( EpaSpan { abstract:RealSrcSpan } )
                                        ]
                                    )
                                    ( EpaComments "" )
                                ) { abstract:SrcSpan }
                            )
                            ( ConDeclH98
                                ( EpAnn
                                    ( Anchor { abstract:RealSrcSpan } UnchangedAnchor ) ""
                                    ( EpaComments "" )
                                )
                                ( L
                                    ( SrcSpanAnn EpAnnNotUsed { abstract:SrcSpan } )
                                    ( Unqual { abstract:OccName } )
                                ) False "" Nothing
                                ( PrefixCon "" "" ) Nothing
                            )
                        , L
                            ( SrcSpanAnn
                                ( EpAnn
                                    ( Anchor { abstract:RealSrcSpan } UnchangedAnchor )
                                    ( AnnListItem
                                        [ AddVbarAnn
                                            ( EpaSpan { abstract:RealSrcSpan } )
                                        ]
                                    )
                                    ( EpaComments "" )
                                ) { abstract:SrcSpan }
                            )
                            ( ConDeclH98
                                ( EpAnn
                                    ( Anchor { abstract:RealSrcSpan } UnchangedAnchor ) ""
                                    ( EpaComments "" )
                                )
                                ( L
                                    ( SrcSpanAnn EpAnnNotUsed { abstract:SrcSpan } )
                                    ( Unqual { abstract:OccName } )
                                ) False "" Nothing
                                ( PrefixCon "" "" ) Nothing
                            )
                        , L
                            ( SrcSpanAnn EpAnnNotUsed { abstract:SrcSpan } )
                            ( ConDeclH98
                                ( EpAnn
                                    ( Anchor { abstract:RealSrcSpan } UnchangedAnchor ) ""
                                    ( EpaComments "" )
                                )
                                ( L
                                    ( SrcSpanAnn EpAnnNotUsed { abstract:SrcSpan } )
                                    ( Unqual { abstract:OccName } )
                                ) False "" Nothing
                                ( PrefixCon "" "" ) Nothing
                            )
                        ] ""
                    )
                )
            )
        ] Nothing Nothing
    )

Maybe its a GHC parser bug. It seems for me, that the last comment isn't attached to record constructor at all. But I'm very likely to be wrong: I know nothing about GHC internal stucture, that's only what I can guess by theese two examples. Maybe someone more skilled can say something more.