yi does not build with -XMonadFailDesugaring enabled (default in GHC 8.6+) #1102

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1. chessai commented on Nov 23, 2018

   

   chessai

   on Nov 23, 2018

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   Apologies for the fact that I forgot to copy the error I was getting the other day. There's likely more than one place, the easiest way to see all of them is either with GHC 8.6 or setting default-extensions: MonadFailDesugaring in your .cabal files
2. chessai

   changed the title [-]yi does not build with -XMonadFailDesugaring enabled[/-] [+]yi does not build with -XMonadFailDesugaring enabled (default in GHC 8.6+)[/+] on Nov 23, 2018
3. zenhack commented on Nov 28, 2018

   

   zenhack

   on Nov 28, 2018

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   Just ran into this. I don't really have anything to add, except ftr this is the error output I got:

   [33 of 70] Compiling Yi.Buffer.Misc   ( src/Yi/Buffer/Misc.hs, dist/build/Yi/Buffer/Misc.o )
   
   src/Yi/Buffer/Misc.hs:453:25-95: error:
       • No instance for (Control.Monad.Fail.MonadFail BufferM)
           arising from a do statement
           with the failable pattern ‘Just mrks’
       • In a stmt of a 'do' block:
           Just mrks <- uses
                          winMarksA (M.lookup $ wkey (b ^. lastActiveWindowA))
         In the expression:
           do Just mrks <- uses
                             winMarksA (M.lookup $ wkey (b ^. lastActiveWindowA))
              forM mrks getMarkValueB
         In a stmt of a 'do' block:
           newMarkValues <- if wkey (b ^. lastActiveWindowA) == def then
                                return
                                  MarkSet
                                    {insMark = MarkValue 0 Forward, selMark = MarkValue 0 Backward,
                                     fromMark = MarkValue 0 Backward}
                            else
                                do Just mrks <- uses
                                                  winMarksA (M.lookup $ wkey (b ^. lastActiveWindowA))
                                   forM mrks getMarkValueB
       |
   453 |                         Just mrks  <- uses winMarksA (M.lookup $ wkey (b ^. lastActiveWindowA))
       |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   
   src/Yi/Buffer/Misc.hs:873:3-30: error:
       • No instance for (Control.Monad.Fail.MonadFail BufferM)
           arising from a do statement
           with the failable pattern ‘Just !ms’
       • In a stmt of a 'do' block: Just !ms <- getMarks =<< ask
         In the expression:
           do Just !ms <- getMarks =<< ask
              return ms
         In an equation for ‘askMarks’:
             askMarks
               = do Just !ms <- getMarks =<< ask
                    return ms
       |
   873 |   Just !ms <- getMarks =<< ask
       |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   cabal: Failed to build yi-core-0.18.0 (which is required by exe:yi from
   yi-0.18.0). See the build log above for details.
   
   
4. xaverdh commented on Feb 17, 2019

   

   xaverdh

   on Feb 17, 2019

   Last edited by xaverdh

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   I have a quick and dirty (may eat your data) patch here: https://github.com/xaverdh/yi/commits/monad-fail
   Actually it probably won't eat your data.
5. chessai commented on Feb 17, 2019

   

   chessai

   on Feb 17, 2019

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   Do we really want the possibility for 'error' to occur there? Is there not a way to just avoid the failable pattern?
6. xaverdh commented on Feb 17, 2019

   

   xaverdh

   on Feb 17, 2019

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   Its not just failable patterns. printableChar for example calls fail explicitly.
   The implementation of MonadInteract also has an Fails constructor which deals with this.
7. xaverdh commented on Feb 17, 2019

   

   xaverdh

   on Feb 17, 2019

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   Ah ok, you are probably referring to BufferM / EditorM. I don't know about that one.
8. xaverdh commented on Feb 17, 2019

   

   xaverdh

   on Feb 17, 2019

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   Ok, its mostly about Marks. getMarks returns a Maybe value, but askMarks (which is used all over the place in that file) then discards it, so maybe its presence is/should be an invariant?
   runBufferFull looks like it should be, but then I don't understand why getMarks exists / is exported at all.
9. xaverdh commented on Feb 17, 2019

   

   xaverdh

   on Feb 17, 2019

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   I opened a pull request #1108 based on a different branch, where I attempt to do things properly.
   We can discuss details there.