Add unsafeGet function and re-implement toTuple with it

An attempt to improve JRec.Tuple compile time.

bin/genrecord

@@ -42,12 +42,10 @@ genInstance i =
           i
       toTuple =
         format
-          "toTuple r = let {} = R.getFields r in unsafeCoerce {}"
-          exprList
-          exprTuple
+          "toTuple r = let n = R.FldProxy :: R.FldProxy \"\" in unsafeCoerce {}"
+          exprGetTuple
       constraints =
         tupleF $
-          format "R.RecApply {} {} R.NoConstraint" typeList typeList :
           [format "n{} ~ n{}'" j j :: Builder | j <- [1 .. i]]
             ++ [format "v{} ~ v{}'" j j :: Builder | j <- [1 .. i]]
    in format
@@ -71,3 +69,5 @@ genInstance i =
     exprList = listF ["f" <> show j | j <- [1 .. i]]
     -- R.unsafeRCons f1 $ R.unsafeRCons f2 $
     consApps = mconcat [format "R.unsafeRCons f{} =<< " j :: Builder | j <- [1 .. i]]
+    -- (n R.:= R.unsafeGet 0 r, n R.:= R.unsafeGet 1 r)
+    exprGetTuple = tupleF [format "n R.:= R.unsafeGet {} r" j :: Builder | j <- [0 .. i-1]]

src/JRec/Internal.hs

@@ -187,6 +187,20 @@ unsafeRCons (_ := val) (MkRec vec#) =
     !(I# size#) = fromIntegral $ natVal' (proxy# :: Proxy# size)
 {-# INLINE unsafeRCons #-}
 
+-- | Get the i-th value as Any unsafely.
+-- No boundary check. Also ther caller is responsible for coerceing to correct type.
+-- Intented for internal use only.
+unsafeGet ::
+  forall lts.
+  Int ->
+  Rec lts ->
+  Any
+unsafeGet (I# index#) (MkRec vec#) =
+  let size# = sizeofSmallArray# vec#
+  in case indexSmallArray# vec# (size# -# index# -# 1#) of
+       (# a# #) -> a#
+{-# INLINE unsafeGet #-}
+
 -- Not in superrecord
 recCopy :: forall lts rts. RecCopy lts lts rts => Rec lts -> Rec rts
 recCopy r@(MkRec vec#) =
@@ -298,15 +312,9 @@ get ::
   FldProxy l ->
   Rec lts ->
   v
-get _ (MkRec vec#) =
-  let !(I# index#) =
-        fromIntegral (natVal' (proxy# :: Proxy# (RecTyIdxH 0 l lts)))
-      size# = sizeofSmallArray# vec#
-      anyVal :: Any
-      anyVal =
-        case indexSmallArray# vec# (size# -# index# -# 1#) of
-          (# a# #) -> a#
-   in unsafeCoerce# anyVal
+get _ r =
+  let !index = fromIntegral (natVal' (proxy# :: Proxy# (RecTyIdxH 0 l lts)))
+  in unsafeCoerce $ unsafeGet index r
 {-# INLINE get #-}
 
 -- | Alias for 'get'