From 4973298f309f8d88f431f789b3bb421acc936bc6 Mon Sep 17 00:00:00 2001
From: Lennart Spitzner <hexagoxel@hexagoxel.de>
Date: Tue, 1 May 2018 23:21:31 +0200
Subject: [PATCH] Support same-line let decl when indentAmount>=4

---
 .../Brittany/Internal/Layouters/Stmt.hs       | 89 +++++++++++--------
 1 file changed, 50 insertions(+), 39 deletions(-)

diff --git a/src/Language/Haskell/Brittany/Internal/Layouters/Stmt.hs b/src/Language/Haskell/Brittany/Internal/Layouters/Stmt.hs
index 33b700e..7a9b922 100644
--- a/src/Language/Haskell/Brittany/Internal/Layouters/Stmt.hs
+++ b/src/Language/Haskell/Brittany/Internal/Layouters/Stmt.hs
@@ -13,7 +13,10 @@ import           Language.Haskell.Brittany.Internal.Types
 import           Language.Haskell.Brittany.Internal.LayouterBasics
 import           Language.Haskell.Brittany.Internal.Config.Types
 
-import           GHC ( runGhc, GenLocated(L), moduleNameString )
+import           GHC                            ( runGhc
+                                                , GenLocated(L)
+                                                , moduleNameString
+                                                )
 import           HsSyn
 import           Name
 import qualified FastString
@@ -28,6 +31,8 @@ import {-# SOURCE #-} Language.Haskell.Brittany.Internal.Layouters.Expr
 layoutStmt :: ToBriDoc' (StmtLR GhcPs GhcPs (LHsExpr GhcPs))
 layoutStmt lstmt@(L _ stmt) = do
   indentPolicy <- mAsk <&> _conf_layout .> _lconfig_indentPolicy .> confUnpack
+  indentAmount :: Int <-
+    mAsk <&> _conf_layout .> _lconfig_indentAmount .> confUnpack
   docWrapNode lstmt $ case stmt of
     LastStmt body False _ -> do
       layoutExpr body
@@ -47,45 +52,51 @@ layoutStmt lstmt@(L _ stmt) = do
             $ docPar (docLit $ Text.pack "<-") (expDoc)
           ]
         ]
-    LetStmt binds -> layoutLocalBinds binds >>= \case
-      Nothing        -> docLit $ Text.pack "let" -- i just tested
-                                -- it, and it is
-                                -- indeed allowed.
-                                -- heh.
-      Just []        -> docLit $ Text.pack "let" -- this probably never happens
-      Just [bindDoc] -> docAlt
-        [ -- let bind = expr
-          docCols
-          ColDoLet
-          [ appSep $ docLit $ Text.pack "let"
-          , let f = case indentPolicy of
-                  IndentPolicyFree     -> docSetBaseAndIndent
-                  IndentPolicyLeft     -> docForceSingleline
-                  IndentPolicyMultiple -> docForceSingleline
-            in  f $ return bindDoc
+    LetStmt binds -> do
+      let isFree         = indentPolicy == IndentPolicyFree
+      let indentFourPlus = indentAmount >= 4
+      layoutLocalBinds binds >>= \case
+        Nothing        -> docLit $ Text.pack "let"
+          -- i just tested the above, and it is indeed allowed. heh.
+        Just []        -> docLit $ Text.pack "let" -- this probably never happens
+        Just [bindDoc] -> docAlt
+          [ -- let bind = expr
+            docCols
+            ColDoLet
+            [ appSep $ docLit $ Text.pack "let"
+            , let
+                f = case indentPolicy of
+                  IndentPolicyFree -> docSetBaseAndIndent
+                  IndentPolicyLeft -> docForceSingleline
+                  IndentPolicyMultiple | indentFourPlus -> docSetBaseAndIndent
+                                       | otherwise      -> docForceSingleline
+              in  f $ return bindDoc
+            ]
+          , -- let
+              --   bind = expr
+            docAddBaseY BrIndentRegular $ docPar
+            (docLit $ Text.pack "let")
+            (docSetBaseAndIndent $ return bindDoc)
           ]
-        , -- let
-          --   bind = expr
-          docAddBaseY BrIndentRegular $ docPar
-          (docLit $ Text.pack "let")
-          (docSetBaseAndIndent $ return bindDoc)
-        ]
-      Just bindDocs -> runFilteredAlternative $ do
-        -- let aaa = expra
-        --     bbb = exprb
-        --     ccc = exprc
-        -- TODO: Allow this for IndentPolicyMultiple when indentAmount = 4
-        addAlternativeCond (indentPolicy == IndentPolicyFree) $ docSeq
-          [ appSep $ docLit $ Text.pack "let"
-          , docSetBaseAndIndent $ docLines $ return <$> bindDocs
-          ]
-        -- let
-        --   aaa = expra
-        --   bbb = exprb
-        --   ccc = exprc
-        addAlternative $ docAddBaseY BrIndentRegular $ docPar
-          (docLit $ Text.pack "let")
-          (docSetBaseAndIndent $ docLines $ return <$> bindDocs)
+        Just bindDocs -> runFilteredAlternative $ do
+          -- let aaa = expra
+          --     bbb = exprb
+          --     ccc = exprc
+          addAlternativeCond (isFree || indentFourPlus) $ docSeq
+            [ appSep $ docLit $ Text.pack "let"
+            , let f = if indentFourPlus
+                    then docEnsureIndent BrIndentRegular
+                    else docSetBaseAndIndent
+              in  f $ docLines $ return <$> bindDocs
+            ]
+          -- let
+          --   aaa = expra
+          --   bbb = exprb
+          --   ccc = exprc
+          addAlternativeCond (not indentFourPlus)
+            $ docAddBaseY BrIndentRegular
+            $ docPar (docLit $ Text.pack "let")
+                     (docSetBaseAndIndent $ docLines $ return <$> bindDocs)
     RecStmt stmts _ _ _ _ _ _ _ _ _ -> runFilteredAlternative $ do
       -- rec stmt1
       --     stmt2