Prepare implementation for `IndentPolicyLeft`

src/Language/Haskell/Brittany/Internal/Config/Types.hs

@@ -191,7 +191,7 @@ data IndentPolicy = IndentPolicyLeft -- never create a new indentation at more
                   | IndentPolicyFree -- can create new indentations whereever
                   | IndentPolicyMultiple -- can create indentations only
                                          -- at any n * amount.
-  deriving (Show, Generic, Data)
+  deriving (Eq, Show, Generic, Data)
 
 data AltChooser = AltChooserSimpleQuick -- always choose last alternative.
                                         -- leads to tons of sparsely filled

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

@@ -13,6 +13,7 @@ where
 
 import           Language.Haskell.Brittany.Internal.Types
 import           Language.Haskell.Brittany.Internal.LayouterBasics
+import           Language.Haskell.Brittany.Internal.Config.Types
 
 import           RdrName ( RdrName(..) )
 import           GHC ( runGhc, GenLocated(L), moduleNameString, AnnKeywordId(..) )
@@ -30,7 +31,8 @@ import           Language.Haskell.Brittany.Internal.Layouters.Type
 
 
 layoutExpr :: ToBriDoc HsExpr
-layoutExpr lexpr@(L _ expr) = docWrapNode lexpr $ case expr of
+layoutExpr lexpr@(L _ expr) = do
+  docWrapNode lexpr $ case expr of
     HsVar vname -> do
       docLit =<< lrdrNameToTextAnn vname
     HsUnboundVar var -> case var of

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

@@ -26,7 +26,8 @@ import {-# SOURCE #-} Language.Haskell.Brittany.Internal.Layouters.Expr
 
 
 layoutStmt :: ToBriDoc' (StmtLR RdrName RdrName (LHsExpr RdrName))
-layoutStmt lstmt@(L _ stmt) = docWrapNode lstmt $ case stmt of
+layoutStmt lstmt@(L _ stmt) = do
+  docWrapNode lstmt $ case stmt of
     LastStmt body False _ -> do
       layoutExpr body
     BindStmt lPat expr _ _ _ -> do
@@ -57,8 +58,8 @@ layoutStmt lstmt@(L _ stmt) = docWrapNode lstmt $ case stmt of
           [ appSep $ docLit $ Text.pack "let"
           , docSetBaseAndIndent $ return bindDoc
           ]
-      , docAddBaseY BrIndentRegular
+        , docAddBaseY BrIndentRegular $ docPar
-        $ docPar (docLit $ Text.pack "let")
+          (docLit $ Text.pack "let")
           (docSetBaseAndIndent $ return bindDoc)
         ]
       Just bindDocs -> docAlt