Breaks leading operator in arrow do block

[robx]

Describe the bug

ormolu moves a leading operator in arrow do notation to the end of the previous line, breaking some code.

To Reproduce

$ cat test.hs
{-# LANGUAGE Arrows #-}

bar f = proc (a, b) ->
  do
    x <- f a -< b
    >-> (\y -> f b >- a)
$ ormolu test.hs
test.hs:6:5
  Parsing of formatted code failed:  parse error (possibly incorrect indentation or mismatched brackets)
$ ormolu --unsafe test.hs
{-# LANGUAGE Arrows #-}

bar f = proc (a, b) ->
  do
    x <- f a -< b >->
    (\y -> a -< f b)

Expected behavior

The code should be formatted to parseable code (with the same AST).

Environment

current master on macos

Additional context

• It seems like mirroring the code for monadic do notation a bit more closely. E.g., ormolu leaves the leading + as is in

  do
  return ()
  + 4

• The following change appears to fix the issue and doesn't break any code I can find, but I doubt it's correct as is:

  
  --- a/src/Ormolu/Printer/Meat/Declaration/Value.hs
  +++ b/src/Ormolu/Printer/Meat/Declaration/Value.hs
  @@ -329,9 +329,10 @@ p_hsCmd' s = \case
     inci (sequence_ (intersperse breakpoint (located' p_hsCmdTop <$> cmds)))
  HsCmdArrForm NoExtField form Infix _ [left, right] -> do
   located left p_hsCmdTop

• space
• located form p_hsExpr
• placeHanging (cmdTopPlacement (unLoc right)) $
• breakpoint
• inci $ do
• located form p_hsExpr
• space located right phsCmdTop HsCmdArrForm NoExtField Infix -> notImplemented "HsCmdArrForm" HsCmdApp NoExtField cmd expr -> do

[amesgen]

EDIT This is incorrect.

With #728 (but still with --unsafe),

{-# LANGUAGE Arrows #-}

bar f = proc (a, b) ->
  do
    x <- f a -< b
    >-> (\y -> f b >- a)

is formatted into

{-# LANGUAGE Arrows #-}

bar f = proc (a, b) ->
  do
    x <- f a -< b
  >->
    (\y -> a -< f b)

which is better, but still not correct, as the first argument of >-> in the original snippet is proc (a, b) -> do x <- f a -< b and not just do x <- f a -< b.

I will look into this.

[amesgen]

With #728 (but still with --unsafe),

{-# LANGUAGE Arrows #-}

bar f = proc (a, b) ->
  do
    x <- f a -< b
    >-> (\y -> f b >- a)

is formatted into

{-# LANGUAGE Arrows #-}

bar f = proc (a, b) ->
  do
    x <- f a -< b
  >->
    (\y -> a -< f b)

which has differing AST, but only due to f b >- a vs. a -< f b. So this is another instance of #737, closing as a duplicate.