Improved the underlining of blocks.
With this patch it does:

Stopped at break020.hs:(6,20)-(7,29)
_result :: t1 () = _
5  
                     vv
6  in_another_decl _ = do line1 0
7                         line2 0
                                 ^^
8  

Instead of

Stopped at break020.hs:(6,20)-(7,29)
_result :: t1 () = _
5  
6  in_another_decl _ = do line1 0
                       ^^
7                         line2 0
                                 ^^
8