Workaround for #68: trim exactprinted text for unknown nodes

src-literatetests/15-regressions.blt

@@ -490,3 +490,6 @@ func
 fmapuv :: U.Unbox a => (a -> b) -> U.Vector a -> V.Vector b
 fmapuv f xs = G.generate (G.length xs) (f . (xs G.!))
 
+
+#test parallellistcomp-workaround
+cs0 = 0 : [ c / Interval n | c <- cs | n <- [1..] ]

src/Language/Haskell/Brittany/Internal/LayouterBasics.hs

@@ -82,6 +82,8 @@ import           ApiAnnotation ( AnnKeywordId(..) )
 import           Data.Data
 import           Data.Generics.Schemes
 
+import qualified Data.Char as Char
+
 import           DataTreePrint
 
 import           Data.HList.HList
@@ -154,19 +156,20 @@ briDocByExactInlineOnly infoStr ast = do
   let exactPrinted = Text.pack $ ExactPrint.exactPrint ast anns
   fallbackMode <-
     mAsk <&> _conf_errorHandling .> _econf_ExactPrintFallback .> confUnpack
-  let exactPrintNode = allocateNode $ BDFExternal
+  let exactPrintNode t = allocateNode $ BDFExternal
         (ExactPrint.Types.mkAnnKey ast)
         (foldedAnnKeys ast)
         False
-        exactPrinted
-  let
-    errorAction = do
+        t
+  let errorAction = do
         mTell $ [ErrorUnknownNode infoStr ast]
-      docLit $ Text.pack "{- BRITTANY ERROR UNHANDLED SYNTACTICAL CONSTRUCT -}"
+        docLit
+          $ Text.pack "{- BRITTANY ERROR UNHANDLED SYNTACTICAL CONSTRUCT -}"
   case (fallbackMode, Text.lines exactPrinted) of
     (ExactPrintFallbackModeNever, _  ) -> errorAction
-    (_                          , [_]) -> exactPrintNode
-    (ExactPrintFallbackModeRisky, _  ) -> exactPrintNode
+    (_                          , [t]) -> exactPrintNode
+      (Text.dropWhile Char.isSpace . Text.dropWhileEnd Char.isSpace $ t)
+    (ExactPrintFallbackModeRisky, _) -> exactPrintNode exactPrinted
     _ -> errorAction
 
 rdrNameToText :: RdrName -> Text