From 0eb29082b14c02587847a1d888127f5b04075954 Mon Sep 17 00:00:00 2001
From: William Rusnack <williamrusnack@gmail.com>
Date: Thu, 11 Apr 2024 14:19:38 -0400
Subject: [PATCH] instance IsList Builder

---
 Data/ByteString/Builder.hs          |  9 ---------
 Data/ByteString/Builder/Internal.hs | 27 +++++++++++++++++++--------
 2 files changed, 19 insertions(+), 17 deletions(-)

diff --git a/Data/ByteString/Builder.hs b/Data/ByteString/Builder.hs
index 1032526da..8fdd58d67 100644
--- a/Data/ByteString/Builder.hs
+++ b/Data/ByteString/Builder.hs
@@ -255,7 +255,6 @@ import           Prelude hiding (writeFile)
 
 import           Data.ByteString.Builder.Internal
 import qualified Data.ByteString.Builder.Prim  as P
-import qualified Data.ByteString.Lazy.Internal as L
 import           Data.ByteString.Builder.ASCII
 import           Data.ByteString.Builder.RealFloat
 
@@ -265,14 +264,6 @@ import           Foreign
 import           GHC.Base (unpackCString#, unpackCStringUtf8#,
                            unpackFoldrCString#, build)
 
--- | Execute a 'Builder' and return the generated chunks as a 'L.LazyByteString'.
--- The work is performed lazy, i.e., only when a chunk of the 'L.LazyByteString'
--- is forced.
-{-# NOINLINE toLazyByteString #-} -- ensure code is shared
-toLazyByteString :: Builder -> L.LazyByteString
-toLazyByteString = toLazyByteStringWith
-    (safeStrategy L.smallChunkSize L.defaultChunkSize) L.Empty
-
 {- Not yet stable enough.
    See note on 'hPut' in Data.ByteString.Builder.Internal
 -}
diff --git a/Data/ByteString/Builder/Internal.hs b/Data/ByteString/Builder/Internal.hs
index 109c762e2..1d7be35be 100644
--- a/Data/ByteString/Builder/Internal.hs
+++ b/Data/ByteString/Builder/Internal.hs
@@ -1,4 +1,6 @@
 {-# LANGUAGE Unsafe #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE NoMonoLocalBinds #-}
 
 {-# OPTIONS_HADDOCK not-home #-}
 
@@ -99,6 +101,7 @@ module Data.ByteString.Builder.Internal (
   , lazyByteString
 
   -- ** Execution
+  , toLazyByteString
   , toLazyByteStringWith
   , AllocationStrategy
   , safeStrategy
@@ -128,6 +131,7 @@ module Data.ByteString.Builder.Internal (
 ) where
 
 import           Control.Arrow (second)
+import           GHC.Exts (IsList(..))
 
 import           Data.Semigroup (Semigroup(..))
 import           Data.List.NonEmpty (NonEmpty(..))
@@ -414,6 +418,12 @@ instance Monoid Builder where
   {-# INLINE mconcat #-}
   mconcat = foldr mappend mempty
 
+instance IsList Builder where
+  type Item Builder = Word8
+  fromList = lazyByteStringInsert . fromList
+  fromListN n = byteString . S.unsafePackLenBytes n
+  toList = toList . toLazyByteString
+
 -- | Flush the current buffer. This introduces a chunk boundary.
 {-# INLINE flush #-}
 flush :: Builder
@@ -1040,18 +1050,19 @@ safeStrategy firstSize bufSize =
     nextBuffer Nothing             = newBuffer $ sanitize firstSize
     nextBuffer (Just (_, minSize)) = newBuffer minSize
 
+-- | Execute a 'Builder' and return the generated chunks as a 'L.LazyByteString'.
+-- The work is performed lazy, i.e., only when a chunk of the 'L.LazyByteString'
+-- is forced.
+{-# NOINLINE toLazyByteString #-} -- ensure code is shared
+toLazyByteString :: Builder -> L.LazyByteString
+toLazyByteString = toLazyByteStringWith
+    (safeStrategy L.smallChunkSize L.defaultChunkSize) L.Empty
+
 -- | /Heavy inlining./ Execute a 'Builder' with custom execution parameters.
 --
 -- This function is inlined despite its heavy code-size to allow fusing with
 -- the allocation strategy. For example, the default 'Builder' execution
--- function 'Data.ByteString.Builder.toLazyByteString' is defined as follows.
---
--- @
--- {-\# NOINLINE toLazyByteString \#-}
--- toLazyByteString =
---   toLazyByteStringWith ('safeStrategy' 'L.smallChunkSize' 'L.defaultChunkSize') L.empty
--- @
---
+-- function 'Data.ByteString.Builder.toLazyByteString'
 -- where @L.empty@ is the zero-length 'L.LazyByteString'.
 --
 -- In most cases, the parameters used by 'Data.ByteString.Builder.toLazyByteString' give good