Deny one layout for OpApp cases unless precedence<=1

Previously allowed: `foo = abc + def-as-par`
Still allowed:      `foo = abc $ def-as-par`
Still allowed:      `foo = abc <&> \x -> def-as-par`

data/15-regressions.blt

@@ -329,7 +329,9 @@ func =
                                         foooooooooooooooooooooooooooooooo
 
 #test opapp-specialcasing-3
-func = fooooooooooooooooooooooooooooooooo + foooooooooooooooooooooooooooooooo
+func =
+  fooooooooooooooooooooooooooooooooo
+    + foooooooooooooooooooooooooooooooo
         [ foooooooooooooooooooooooooooooooo
         , foooooooooooooooooooooooooooooooo
         , foooooooooooooooooooooooooooooooo
@@ -966,3 +968,8 @@ func =
         )
     <$> mylist
     )
+
+#test operator newline behaviour
+func =
+  fromIntegral aaaaaaaaaaaaaaaaaaa
+    / fromIntegral (aaaaaaaaaaaaaaaaaaa + bbbbbbbbbbbbbbbbbb)

data/30-tests-context-free.blt

@@ -1278,7 +1278,9 @@ func =
         foooooooooooooooooooooooooooooooo
 
 #test opapp-specialcasing-3
-func = fooooooooooooooooooooooooooooooooo + foooooooooooooooooooooooooooooooo
+func =
+  fooooooooooooooooooooooooooooooooo
+    + foooooooooooooooooooooooooooooooo
         [ foooooooooooooooooooooooooooooooo
         , foooooooooooooooooooooooooooooooo
         , foooooooooooooooooooooooooooooooo

source/library/Language/Haskell/Brittany/Internal/ToBriDoc/OpTree.hs

@@ -198,6 +198,9 @@ layoutOpTree allowSinglelinePar = \case
           pure (pure op, subDoc)
     sharedOpsFlat <- flattenList docOps
     sharedOps     <- simpleTransform docOps
+    let lastWrap = if getPrec fixity <= 1
+          then docForceParSpacing
+          else docForceSingleline
     coreAlternative hasParen
                     locO
                     locC
@@ -205,11 +208,12 @@ layoutOpTree allowSinglelinePar = \case
                     docL
                     sharedOps
                     sharedOpsFlat
-                    docForceParSpacing
+                    lastWrap
   OpLeaf l -> pure l
  where
-  isPrec0 = \case
-    Fixity _ prec _ -> prec == 0
+  isPrec0 x = getPrec x == 0
+  getPrec = \case
+    Fixity _ prec _ -> prec
   coreAlternative
     :: Bool
     -> Maybe GHC.RealSrcLoc
@@ -271,7 +275,11 @@ layoutOpTree allowSinglelinePar = \case
               ([docForceSingleline docL] ++ case splitFirstLast sharedOpsFlat of
                 FirstLastEmpty -> []
                 FirstLastSingleton (od, ed) ->
-              [docSeparator, docForceSingleline od, docSeparator, lastWrap ed]
+                  [ docSeparator
+                  , docForceSingleline od
+                  , docSeparator
+                  , lastWrap ed
+                  ]
                 FirstLast (od1, ed1) ems (odN, edN) ->
                   (  [ docSeparator
                      , docForceSingleline od1
@@ -293,8 +301,6 @@ layoutOpTree allowSinglelinePar = \case
                      ]
                   )
               )
-        -- this case rather leads to some unfortunate layouting than to anything
-        -- useful; disabling for now. (it interfers with cols stuff.)
         -- one
         -- + two
         -- + three
@@ -314,8 +320,7 @@ layoutOpTree allowSinglelinePar = \case
           [(od, ed)] | curIsPrec0 ->
             addAlternativeCond (not hasParen && isSingleOp)
               $ docSetParSpacing
-              $ docPar
-                (docHandleComms locO $ docForceSingleline $ docL)
+              $ docPar (docHandleComms locO $ docForceSingleline $ docL)
                        (docSeq [od, docSeparator, singlelineUnlessFree ed])
           _ -> pure ()
         -- > ( one