Support RecursiveDo/`rec` keyword

src-literatetests/14-extensions.blt

@@ -48,3 +48,21 @@ func
      )
   -> ()
 
+
+###############################################################################
+## RecursiveDo
+#test recursivedo 1
+{-# LANGUAGE RecursiveDo #-}
+foo = do
+  rec a <- f b
+      b <- g a
+  return (a, b)
+
+#test recursivedo 2
+{-# LANGUAGE RecursiveDo #-}
+foo = do
+  rec -- comment
+      a <- f b
+      b <- g a
+  return (a, b)
+

src/Language/Haskell/Brittany/Internal/Layouters/Stmt.hs

@@ -70,6 +70,12 @@ layoutStmt lstmt@(L _ stmt) = docWrapNode lstmt $ case stmt of
         (docLit $ Text.pack "let")
         (docSetBaseAndIndent $ docLines $ return <$> bindDocs)
       ]
+  RecStmt stmts _ _ _ _ _ _ _ _ _ -> do
+    docSeq
+      [ docLit (Text.pack "rec")
+      , docSeparator
+      , docSetBaseAndIndent $ docLines $ layoutStmt <$> stmts
+      ]
   BodyStmt expr _ _ _      -> do
     expDoc <- docSharedWrapper layoutExpr expr
     docAddBaseY BrIndentRegular $ expDoc