Move TH experiments to test-th

4 files changed, 429 insertions, 0 deletions

diff --git a/test-th/Arith.hs b/test-th/Arith.hs
new file mode 100644
index 0000000..c34baa8
--- /dev/null
+++ b/test-th/Arith.hs
@@ -0,0 +1,103 @@
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE QuantifiedConstraints #-}
+module Arith where
+
+import Data.Type.Equality
+
+import Data.Expr.SharingRecovery
+
+
+data Typ t where
+  TInt :: Typ Int
+  TBool :: Typ Bool
+  TPair :: Typ a -> Typ b -> Typ (a, b)
+  TFun :: Typ a -> Typ b -> Typ (a -> b)
+deriving instance Show (Typ t)
+
+instance TestEquality Typ where
+  testEquality TInt TInt = Just Refl
+  testEquality TBool TBool = Just Refl
+  testEquality (TPair a b) (TPair a' b')
+    | Just Refl <- testEquality a a'
+    , Just Refl <- testEquality b b'
+    = Just Refl
+  testEquality (TFun a b) (TFun a' b')
+    | Just Refl <- testEquality a a'
+    , Just Refl <- testEquality b b'
+    = Just Refl
+  testEquality _ _ = Nothing
+
+class KnownType t where τ :: Typ t
+instance KnownType Int where τ = TInt
+instance KnownType Bool where τ = TBool
+instance (KnownType a, KnownType b) => KnownType (a, b) where τ = TPair τ τ
+instance (KnownType a, KnownType b) => KnownType (a -> b) where τ = TFun τ τ
+
+data PrimOp a b where
+  POAddI :: PrimOp (Int, Int) Int
+  POMulI :: PrimOp (Int, Int) Int
+  POEqI :: PrimOp (Int, Int) Bool
+deriving instance Show (PrimOp a b)
+
+opType2 :: PrimOp a b -> Typ b
+opType2 = \case
+  POAddI -> TInt
+  POMulI -> TInt
+  POEqI -> TBool
+
+data Fixity = Infix | Prefix
+  deriving (Show)
+
+primOpPrec :: PrimOp a b -> (Int, (Int, Int))
+primOpPrec POAddI = (6, (6, 7))
+primOpPrec POMulI = (7, (7, 8))
+primOpPrec POEqI = (4, (5, 5))
+
+prettyPrimOp :: Fixity -> PrimOp a b -> ShowS
+prettyPrimOp fix op =
+  let s = case op of
+            POAddI -> "+"
+            POMulI -> "*"
+            POEqI -> "=="
+  in showString $ case fix of
+       Infix -> s
+       Prefix -> "(" ++ s ++ ")"
+
+data ArithF r t where
+  A_Prim :: PrimOp a b -> r a -> ArithF r b
+  A_Pair :: r a -> r b -> ArithF r (a, b)
+  A_If :: r Bool -> r a -> r a -> ArithF r a
+deriving instance (forall a. Show (r a)) => Show (ArithF r t)
+
+instance Functor1 ArithF
+instance Traversable1 ArithF where
+  traverse1 f (A_Prim op x) = A_Prim op <$> f x
+  traverse1 f (A_Pair x y) = A_Pair <$> f x <*> f y
+  traverse1 f (A_If x y z) = A_If <$> f x <*> f y <*> f z
+
+prettyArithF :: Monad m
+             => (forall a. Int -> BExpr Typ env ArithF a -> m ShowS)
+             -> Int -> ArithF (BExpr Typ env ArithF) t -> m ShowS
+prettyArithF pr d = \case
+  A_Prim op (BOp _ (A_Pair a b)) -> do
+    let (dop, (dopL, dopR)) = primOpPrec op
+    a' <- pr dopL a
+    b' <- pr dopR b
+    return $ showParen (d > dop) $ a' . showString " " . prettyPrimOp Infix op . showString " " . b'
+  A_Prim op (BLet ty rhs e) ->
+    pr d (BLet ty rhs (BOp (opType2 op) (A_Prim op e)))
+  A_Prim op arg -> do
+    arg' <- pr 11 arg
+    return $ showParen (d > 10) $ prettyPrimOp Prefix op . showString " " . arg'
+  A_Pair a b -> do
+    a' <- pr 0 a
+    b' <- pr 0 b
+    return $ showString "(" . a' . showString ", " . b' . showString ")"
+  A_If a b c -> do
+    a' <- pr 0 a
+    b' <- pr 0 b
+    c' <- pr 0 c
+    return $ showParen (d > 0) $ showString "if " . a' . showString " then " . b' . showString " else " . c'
diff --git a/test-th/Arith/NonBase.hs b/test-th/Arith/NonBase.hs
new file mode 100644
index 0000000..f5d458e
--- /dev/null
+++ b/test-th/Arith/NonBase.hs
@@ -0,0 +1,50 @@
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE StandaloneKindSignatures #-}
+{-# LANGUAGE TemplateHaskell #-}
+module Arith.NonBase where
+
+import Data.Kind
+import Data.Type.Equality
+
+import NonBaseTH
+
+
+data Typ t where
+  TInt :: Typ Int
+  TBool :: Typ Bool
+  TPair :: Typ a -> Typ b -> Typ (a, b)
+  TFun :: Typ a -> Typ b -> Typ (a -> b)
+deriving instance Show (Typ t)
+
+instance TestEquality Typ where
+  testEquality TInt TInt = Just Refl
+  testEquality TBool TBool = Just Refl
+  testEquality (TPair a b) (TPair a' b')
+    | Just Refl <- testEquality a a'
+    , Just Refl <- testEquality b b'
+    = Just Refl
+  testEquality (TFun a b) (TFun a' b')
+    | Just Refl <- testEquality a a'
+    , Just Refl <- testEquality b b'
+    = Just Refl
+  testEquality _ _ = Nothing
+
+data PrimOp a b where
+  POAddI :: PrimOp (Int, Int) Int
+  POMulI :: PrimOp (Int, Int) Int
+  POEqI :: PrimOp (Int, Int) Bool
+deriving instance Show (PrimOp a b)
+
+type Arith :: Type -> Type
+data Arith t where
+  A_Var :: Typ t -> String -> Arith t
+  A_Let :: String -> Typ a -> Arith a -> Arith b -> Arith b
+  A_Prim :: PrimOp a b -> Arith a -> Arith b
+  A_Pair :: Arith a -> Arith b -> Arith (a, b)
+  A_If :: Arith Bool -> Arith a -> Arith a -> Arith a
+  A_Mono :: Arith Bool -> Arith Bool
+
+defineBaseAST
+  "ArithF" ''Arith ['A_Var, 'A_Let] (("AF_"++) . drop 2)
+  "arithConv" ''Typ (\_ _ _ -> [| error "Lambda impossible" |])
diff --git a/test-th/Main.hs b/test-th/Main.hs
new file mode 100644
index 0000000..5a4d335
--- /dev/null
+++ b/test-th/Main.hs
@@ -0,0 +1,51 @@
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE QuantifiedConstraints #-}
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE StandaloneDeriving #-}
+module Main where
+
+import Data.Expr.SharingRecovery
+import Data.Expr.SharingRecovery.Internal
+
+import Arith
+
+
+-- TODO: test cyclic expressions
+
+
+a_bin :: (KnownType a, KnownType b, KnownType c)
+      => PrimOp (a, b) c
+      -> PHOASExpr Typ v ArithF a
+      -> PHOASExpr Typ v ArithF b
+      -> PHOASExpr Typ v ArithF c
+a_bin op a b = PHOASOp τ (A_Prim op (PHOASOp τ (A_Pair a b)))
+
+lam :: (KnownType a, KnownType b)
+    => (PHOASExpr Typ v f a -> PHOASExpr Typ v f b) -> PHOASExpr Typ v f (a -> b)
+lam f = PHOASLam τ τ $ \arg -> f (PHOASVar τ arg)
+
+(+!) :: PHOASExpr Typ v ArithF Int -> PHOASExpr Typ v ArithF Int -> PHOASExpr Typ v ArithF Int
+(+!) = a_bin POAddI
+
+(*!) :: PHOASExpr Typ v ArithF Int -> PHOASExpr Typ v ArithF Int -> PHOASExpr Typ v ArithF Int
+(*!) = a_bin POMulI
+
+-- λx. x + x
+ea_1 :: PHOASExpr Typ v ArithF (Int -> Int)
+ea_1 = lam $ \arg -> arg +! arg
+
+-- λx. let y = x + x in y * y
+ea_2 :: PHOASExpr Typ v ArithF (Int -> Int)
+ea_2 = lam $ \arg -> let y = arg +! arg
+                     in y *! y
+
+ea_3 :: PHOASExpr Typ v ArithF (Int -> Int)
+ea_3 = lam $ \arg ->
+  let y = arg +! arg
+      x = y *! arg
+  -- in (y +! x) +! (x +! y)
+  in (x +! y) +! (y +! x)
+
+main :: IO ()
+main = putStrLn $ prettyBExpr prettyArithF (sharingRecovery ea_3)
diff --git a/test-th/NonBaseTH.hs b/test-th/NonBaseTH.hs
new file mode 100644
index 0000000..4741ea0
--- /dev/null
+++ b/test-th/NonBaseTH.hs
@@ -0,0 +1,225 @@
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE TemplateHaskellQuotes #-}
+{-# LANGUAGE TupleSections #-}
+module NonBaseTH (
+  defineBaseAST,
+) where
+
+import Control.Monad (when)
+import Data.List (sort, foldl', tails)
+import qualified Data.Map.Strict as Map
+import Data.Maybe (catMaybes)
+import Language.Haskell.TH
+
+import Data.Expr.SharingRecovery
+
+
+-- | Non-base AST data type
+data NBAST = NBAST String [TyVarBndr ()] [NBCon]
+
+data NBCon = NBCon
+    [String]                -- ^ Names of the constructors defined with this clause
+    [TyVarBndrSpec]         -- ^ Type variables in scope in the clause
+    Cxt                     -- ^ Constraints on the constructor type
+    [(Bang, NBField Type)]  -- ^ Constructor fields
+    [Name]                  -- ^ All but the last type parameter in the result type
+    Type                    -- ^ The last type parameter in the result type
+
+data NBField t
+  = NBFList (NBField t)
+  | NBFTuple [NBField t]
+  | NBFRecur t  -- ^ The last type parameter of this recursive position. (The
+                -- other type parameters are fixed anyway.)
+  | NBFConst Type
+
+parseNBAST :: [String] -> Info -> Q NBAST
+parseNBAST excludes info = do
+  (astname, params, constrs) <- case info of
+    TyConI (DataD [] astname params Nothing constrs _) -> return (astname, params, constrs)
+    _ -> fail "Unsupported datatype"
+
+  -- In this function we use parameter/index terminology: parameters are
+  -- uniform, indices vary inside an AST.
+  let parseField retpars field = do
+        let (core, args) = splitApps field
+        case core of
+          ConT n
+            | n == astname ->
+                if not (null args) && init args == map VarT retpars
+                  then return (NBFRecur (last args))
+                  else fail $ "Field\n  " ++ pprint field
+                              ++ "\nis recursive, but with different type parameters than "
+                              ++ "the return type of this constructor. All but the last type "
+                              ++ "parameter of the GADT must be uniform over the entire AST."
+
+          ListT
+            | [arg] <- args -> NBFList <$> parseField retpars arg
+
+          TupleT k
+            | length args == k -> NBFTuple <$> traverse (parseField retpars) args
+
+          _ -> do
+            when (pprint astname `infixOf` pprint field) $
+              reportWarning $ "Field\n  " ++ pprint field ++ "\nseems to refer to "
+                              ++ pprint astname ++ " in unsupported ways; ignoring those occurrences."
+            return (NBFConst field)
+
+  let splitConstr (ForallC vars ctx (GadtC names fields retty))
+        | names'@(_:_) <- filter (`notElem` excludes) (map nameBase names) =
+            return (Just (vars, ctx, names', fields, retty))
+        | otherwise = return Nothing
+      splitConstr c@GadtC{} = splitConstr (ForallC [] [] c)
+      splitConstr c =
+        let names = case c of
+                      NormalC n _ -> Just (show n)
+                      _ -> Just (show c)
+        in fail $ "Unsupported constructors found" ++ maybe "" (\s -> ": " ++ show s) names
+
+  let parseConstr (vars, ctx, names, fields, retty) = do
+        (retpars, retindex) <- parseRetty astname (head names) retty
+        fields' <- traverse (\(ba, t) -> (ba,) <$> parseField retpars t) fields
+        return (NBCon names vars ctx fields' retpars retindex)
+
+  constrs' <- traverse parseConstr =<< catMaybes <$> traverse splitConstr constrs
+  return (NBAST (nameBase astname) params constrs')
+
+
+-- | Define a new GADT that is a base-functor-like version of a given existing
+-- GADT AST.
+--
+-- Remember to use 'lookupTypeName' or 'lookupValueName' instead of normal
+-- quotes in case of punning of data types and constructors.
+defineBaseAST
+  :: String  -- ^ Name of the (base-functor-like) data type to define
+  -> Name  -- ^ Name of the GADT to process
+  -> [Name]  -- ^ Constructors to exclude (Var and Let, plus any other scoping construct)
+  -> (String -> String)  -- ^ Constructor renaming function
+  -> String  -- ^ Name of base -> nonbase conversion function to define
+  -> Name  -- ^ Type of singleton types
+  -> (ExpQ -> ExpQ -> ExpQ -> ExpQ)  -- ^ Lambda: typ (a -> b) -> typ a -> AST b -> AST (a -> b)
+  -> (ExpQ -> ExpQ -> ExpQ -> ExpQ)  -- ^ Let: typ a -> String -> AST a -> AST b -> AST b
+  -> (ExpQ -> ExpQ -> ExpQ -> ExpQ)  -- ^ Var: typ t -> String -> AST b -> AST b
+  -> Q [Dec]
+defineBaseAST basename astname excludes renameConstr bnConvName typName mkLam mkLet mkVar = do
+  NBAST _ params constrs <- parseNBAST (map nameBase excludes) =<< reify astname
+
+  -- Build the data type
+
+  let basename' = mkName basename
+      conNameMap = Map.fromList [(nbname, mkName (renameConstr nbname))
+                                | NBCon ns _ _ _ _ _ <- constrs, nbname <- ns]
+
+  let recvar = mkName "r"
+
+  let processField (NBFRecur idx) = VarT recvar `AppT` idx
+      processField (NBFConst t) = t
+      processField (NBFList f) = AppT ListT (processField f)
+      processField (NBFTuple fs) = foldl' AppT (TupleT (length fs)) (map processField fs)
+
+  let processConstr (NBCon names vars ctx fields retparams retindex) = do
+        let names' = map (conNameMap Map.!) names
+        let fields' = map (\(ba, f) -> (ba, processField f)) fields
+        let retty' = foldl' AppT (ConT basename') (map VarT retparams ++ [VarT recvar, retindex])
+        return [ForallC (map cleanupBndr vars ++ [PlainTV recvar SpecifiedSpec])
+                        ctx (GadtC names' fields' retty')]
+
+  let params' = map cleanupBndr (init params ++ [PlainTV recvar (), last params])
+  constrs' <- concat <$> traverse processConstr constrs
+  let datatype = DataD [] (mkName basename) params' Nothing constrs' []
+
+  -- Build the B->N conversion function
+
+  let bnConvName' = mkName bnConvName
+      envparam = VarT (mkName "env")
+      tparam = VarT (mkName "t")
+      ftype = foldl' AppT (ConT basename') (map (VarT . bndrName) (init params))
+      arrow a b = ArrowT `AppT` a `AppT` b
+
+  let bnConvSig =
+        SigD bnConvName' $
+             (ConT ''BExpr `AppT` ConT typName `AppT` envparam `AppT` ftype `AppT` tparam)
+             `arrow`
+             foldl' AppT (ConT astname) (map (VarT . bndrName) (init params) ++ [tparam])
+
+  let clause' pats ex = Clause pats (NormalB ex) []
+      -- backConMap = Map.fromList [(renameConstr nbname, nbname)
+      --                           | NBCon ns _ _ _ _ _ <- constrs, nbname <- ns]
+      reconstructField (NBFRecur _) = do
+        r <- newName "r"
+        return (VarP r, VarE bnConvName' `AppE` VarE r)
+      reconstructField (NBFConst _) = do
+        x <- newName "x"
+        return (VarP x, VarE x)
+      reconstructField (NBFList f) = do
+        (pat, ex) <- reconstructField f
+        l <- newName "l"
+        return (VarP l, VarE 'map `AppE` LamE [pat] ex `AppE` VarE l)
+      reconstructField (NBFTuple fs) = do
+        (pats, exps) <- unzip <$> traverse reconstructField fs
+        return (TupP pats, TupE (map Just exps))
+
+  let tyarg1 = mkName "ty1"
+      tyarg2 = mkName "ty2"
+      astarg = mkName "ast"
+      mkseq a b = VarE 'seq `AppE` a `AppE` b
+      infixr `mkseq`
+
+  bnConvFun <-
+    fmap (FunD bnConvName') . sequence $
+       [do (pats, exps) <- unzip <$> traverse (reconstructField . snd) fields
+           return $
+             clause' [ConP 'BOp [] [WildP, ConP (conNameMap Map.! nbname) [] pats]]
+                     (foldl' AppE (ConE (mkName nbname)) exps)
+       | NBCon names _ _ fields _ _ <- constrs
+       , nbname <- names]
+       ++
+       [do body <- mkLam (varE tyarg1) (varE tyarg2) (varE astarg)
+           return $ clause' [ConP 'BLam [] [VarP tyarg1, VarP tyarg2, VarP astarg]]
+                            -- put them in a useless seq so that they're not unused
+                            (TupE [Just (VarE tyarg1), Just (VarE tyarg2), Just (VarE astarg)] `mkseq` body)]
+
+  return [datatype, bnConvSig, bnConvFun]
+
+-- | Remove `:: Type` annotations because they unnecessarily require the user
+-- to enable KindSignatures. Any other annotations we leave, in case the user
+-- wrote them and they are necessary.
+cleanupBndr :: TyVarBndr a -> TyVarBndr a
+cleanupBndr (KindedTV name x k) | isType k = PlainTV name x
+  where isType StarT = True
+        isType (ConT n) | n == ''Type = True
+        isType _ = False
+cleanupBndr b = b
+
+bndrName :: TyVarBndr a -> Name
+bndrName (PlainTV name _) = name
+bndrName (KindedTV name _ _) = name
+
+parseRetty :: Name -> String -> Type -> Q ([Name], Type)
+parseRetty astname consname retty = do
+  case splitApps retty of
+    (ConT name, args)
+      | name /= astname -> fail $ "Could not parse return type of constructor " ++ consname
+      | null args -> fail "Expected GADT to have type parameters"
+
+      | Just varnames <- traverse (\case VarT varname -> Just varname ; _ -> Nothing) (init args)
+      , allDistinct varnames ->
+          return (varnames, last args)
+
+      | otherwise -> fail $ "All type parameters but the last one must be uniform over all constructors. "
+                            ++ "(Return type of constructor " ++ consname ++ ")"
+    _ -> fail $ "Could not parse return type of constructor " ++ consname
+
+splitApps :: Type -> (Type, [Type])
+splitApps = flip go []
+  where go (ParensT t) tl = go t tl
+        go (AppT t arg) tl = go t (arg : tl)
+        go t tl = (t, tl)
+
+allDistinct :: Ord a => [a] -> Bool
+allDistinct l =
+  let sorted = sort l
+  in all (uncurry (/=)) (zip sorted (drop 1 sorted))
+
+infixOf :: Eq a => [a] -> [a] -> Bool
+short `infixOf` long = any (`startsWith` short) (tails long)
+  where a `startsWith` b = take (length b) a == b