module Type.Constrain.Expression where
import qualified Data.List as List
import qualified Data.Map as Map
import qualified Data.Set as Set
import Control.Applicative ((<$>))
import qualified Control.Monad as Monad
import Control.Monad.Error
import qualified Text.PrettyPrint as PP
import SourceSyntax.Location as Loc
import SourceSyntax.Pattern (Pattern(PVar), boundVars)
import SourceSyntax.Expression
import qualified SourceSyntax.Type as SrcT
import Type.Type hiding (Descriptor(..))
import Type.Fragment
import qualified Type.Environment as Env
import qualified Type.Constrain.Literal as Literal
import qualified Type.Constrain.Pattern as Pattern
constrain :: Env.Environment -> LExpr -> Type -> ErrorT [PP.Doc] IO TypeConstraint
constrain env (L span expr) tipe =
let list t = Env.get env Env.types "_List" <| t
and = L span . CAnd
true = L span CTrue
t1 === t2 = L span (CEqual t1 t2)
x <? t = L span (CInstance x t)
clet schemes c = L span (CLet schemes c)
in
case expr of
Literal lit -> liftIO $ Literal.constrain env span lit tipe
Var name | name == saveEnvName -> return (L span CSaveEnv)
| otherwise -> return (name <? tipe)
Range lo hi ->
exists $ \x -> do
clo <- constrain env lo x
chi <- constrain env hi x
return $ and [clo, chi, list x === tipe]
ExplicitList exprs ->
exists $ \x -> do
cs <- mapM (\e -> constrain env e x) exprs
return . and $ list x === tipe : cs
Binop op e1 e2 ->
exists $ \t1 ->
exists $ \t2 -> do
c1 <- constrain env e1 t1
c2 <- constrain env e2 t2
return $ and [ c1, c2, op <? (t1 ==> t2 ==> tipe) ]
Lambda p e ->
exists $ \t1 ->
exists $ \t2 -> do
fragment <- try span $ Pattern.constrain env p t1
c2 <- constrain env e t2
let c = ex (vars fragment) (clet [monoscheme (typeEnv fragment)]
(typeConstraint fragment /\ c2 ))
return $ c /\ tipe === (t1 ==> t2)
App e1 e2 ->
exists $ \t -> do
c1 <- constrain env e1 (t ==> tipe)
c2 <- constrain env e2 t
return $ c1 /\ c2
MultiIf branches -> and <$> mapM constrain' branches
where
bool = Env.get env Env.types "Bool"
constrain' (b,e) = do
cb <- constrain env b bool
ce <- constrain env e tipe
return (cb /\ ce)
Case exp branches ->
exists $ \t -> do
ce <- constrain env exp t
let branch (p,e) = do
fragment <- try span $ Pattern.constrain env p t
clet [toScheme fragment] <$> constrain env e tipe
and . (:) ce <$> mapM branch branches
Data name exprs ->
do vars <- forM exprs $ \_ -> liftIO (var Flexible)
let pairs = zip exprs (map VarN vars)
(ctipe, cs) <- Monad.foldM step (tipe,true) (reverse pairs)
return $ ex vars (cs /\ name <? ctipe)
where
step (t,c) (e,x) = do
c' <- constrain env e x
return (x ==> t, c /\ c')
Access e label ->
exists $ \t ->
constrain env e (record (Map.singleton label [tipe]) t)
Remove e label ->
exists $ \t ->
constrain env e (record (Map.singleton label [t]) tipe)
Insert e label value ->
exists $ \tVal ->
exists $ \tRec -> do
cVal <- constrain env value tVal
cRec <- constrain env e tRec
let c = tipe === record (Map.singleton label [tVal]) tRec
return (and [cVal, cRec, c])
Modify e fields ->
exists $ \t -> do
oldVars <- forM fields $ \_ -> liftIO (var Flexible)
let oldFields = SrcT.fieldMap (zip (map fst fields) (map VarN oldVars))
cOld <- ex oldVars <$> constrain env e (record oldFields t)
newVars <- forM fields $ \_ -> liftIO (var Flexible)
let newFields = SrcT.fieldMap (zip (map fst fields) (map VarN newVars))
let cNew = tipe === record newFields t
cs <- zipWithM (constrain env) (map snd fields) (map VarN newVars)
return $ cOld /\ ex newVars (and (cNew : cs))
Record fields ->
do vars <- forM fields $ \_ -> liftIO (var Flexible)
cs <- zipWithM (constrain env) (map snd fields) (map VarN vars)
let fields' = SrcT.fieldMap (zip (map fst fields) (map VarN vars))
recordType = record fields' (TermN EmptyRecord1)
return . ex vars . and $ tipe === recordType : cs
Markdown _ _ es ->
do vars <- forM es $ \_ -> liftIO (var Flexible)
let tvars = map VarN vars
cs <- zipWithM (constrain env) es tvars
return . ex vars $ and ("Text.markdown" <? tipe : cs)
Let defs body ->
do c <- constrain env body tipe
(schemes, rqs, fqs, header, c2, c1) <-
Monad.foldM (constrainDef env)
([], [], [], Map.empty, true, true)
(concatMap expandPattern defs)
return $ clet schemes
(clet [Scheme rqs fqs (clet [monoscheme header] c2) header ]
(c1 /\ c))
PortIn _ _ -> return true
PortOut _ _ signal ->
constrain env signal tipe
constrainDef env info (Definition pattern expr maybeTipe) =
let qs = []
(schemes, rigidQuantifiers, flexibleQuantifiers, headers, c2, c1) = info
in
do rigidVars <- forM qs (\_ -> liftIO $ var Rigid)
case (pattern, maybeTipe) of
(PVar name, Just tipe) -> do
flexiVars <- forM qs (\_ -> liftIO $ var Flexible)
let inserts = zipWith (\arg typ -> Map.insert arg (VarN typ)) qs flexiVars
env' = env { Env.value = List.foldl' (\x f -> f x) (Env.value env) inserts }
(vars, typ) <- Env.instantiateType env tipe Map.empty
let scheme = Scheme { rigidQuantifiers = [],
flexibleQuantifiers = flexiVars ++ vars,
constraint = Loc.noneNoDocs CTrue,
header = Map.singleton name typ }
c <- constrain env' expr typ
return ( scheme : schemes
, rigidQuantifiers
, flexibleQuantifiers
, headers
, c2
, fl rigidVars c /\ c1 )
(PVar name, Nothing) -> do
v <- liftIO $ var Flexible
let tipe = VarN v
inserts = zipWith (\arg typ -> Map.insert arg (VarN typ)) qs rigidVars
env' = env { Env.value = List.foldl' (\x f -> f x) (Env.value env) inserts }
c <- constrain env' expr tipe
return ( schemes
, rigidVars ++ rigidQuantifiers
, v : flexibleQuantifiers
, Map.insert name tipe headers
, c /\ c2
, c1 )
_ -> error (show pattern)
expandPattern :: Def -> [Def]
expandPattern def@(Definition pattern lexpr@(L s _) maybeType) =
case pattern of
PVar _ -> [def]
_ -> Definition (PVar x) lexpr maybeType : map toDef vars
where
vars = Set.toList $ boundVars pattern
x = "$" ++ concat vars
mkVar = L s . Var
toDef y = Definition (PVar y) (L s $ Case (mkVar x) [(pattern, mkVar y)]) Nothing
try :: SrcSpan -> ErrorT (SrcSpan -> PP.Doc) IO a -> ErrorT [PP.Doc] IO a
try span computation = do
result <- liftIO $ runErrorT computation
case result of
Left err -> throwError [err span]
Right value -> return value