Fix bug in PRMMinimize feature for InfixN operators

data/12-features/minimize-parentheses.blt

@@ -25,3 +25,7 @@ func = func ((((((((nested + expression))))))))
 #expected
 -- brittany { lconfig_operatorParenthesisRefactorMode: PRMMinimize }
 func = func (nested + expression)
+
+#test does not remove parens on InfixN
+-- brittany { lconfig_operatorParenthesisRefactorMode: PRMMinimize }
+func = (a == Foo) == (b == Bar)

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

@@ -216,7 +216,13 @@ remSuperfluousParens outerFixity = \case
       locO
       locC
       fixity
-      (remSuperfluousParens (fixLevel fixity) c)
+      (remSuperfluousParens
+        (case fixity of
+          Fixity _ level InfixN -> level + 1
+          Fixity _ level _      -> level
+        )
+        c
+      )
       [ (op, remSuperfluousParens (fixLevel fixity) tree) | (op, tree) <- cs ]
   x -> x
  where