{-# LANGUAGE CPP #-}
{-# LANGUAGE NondecreasingIndentation #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}
module Agda.TypeChecking.Rewriting where
import Prelude hiding (null)
import Control.Applicative hiding (empty)
import Control.Monad
import Control.Monad.Reader (local, asks)
import Data.Foldable ( Foldable, foldMap )
import Data.IntSet (IntSet)
import qualified Data.IntSet as IntSet
import qualified Data.List as List
import Data.Monoid
import Agda.Interaction.Options
import Agda.Syntax.Common
import Agda.Syntax.Internal as I
import Agda.TypeChecking.Monad
import Agda.TypeChecking.Monad.Builtin
import Agda.TypeChecking.Monad.Env
import Agda.TypeChecking.EtaContract
import Agda.TypeChecking.Free
import Agda.TypeChecking.Free.Lazy
import Agda.TypeChecking.MetaVars
import Agda.TypeChecking.Conversion
import qualified Agda.TypeChecking.Positivity.Occurrence as Pos
import Agda.TypeChecking.Pretty
import Agda.TypeChecking.Primitive ( getBuiltinName )
import Agda.TypeChecking.Reduce
import Agda.TypeChecking.Substitute
import Agda.TypeChecking.Telescope
import Agda.TypeChecking.Rewriting.NonLinMatch
import qualified Agda.TypeChecking.Reduce.Monad as Red
import Agda.TypeChecking.Warnings
import Agda.Utils.Functor
import qualified Agda.Utils.HashMap as HMap
import Agda.Utils.Lens
import Agda.Utils.List
import Agda.Utils.Maybe
import Agda.Utils.Monad
import Agda.Utils.Null
import Agda.Utils.Singleton
import Agda.Utils.Size
import Agda.Utils.Lens
import qualified Agda.Utils.HashMap as HMap
#include "undefined.h"
import Agda.Utils.Impossible
requireOptionRewriting :: TCM ()
requireOptionRewriting =
unlessM (optRewriting <$> pragmaOptions) $ typeError NeedOptionRewriting
verifyBuiltinRewrite :: Term -> Type -> TCM ()
verifyBuiltinRewrite v t = do
requireOptionRewriting
let failure reason = typeError . GenericDocError =<< sep
[ prettyTCM v <+> text " does not have the right type for a rewriting relation"
, reason
]
caseMaybeM (relView t)
(failure $ text "because it should accept at least two arguments") $
\ (RelView tel delta a b core) -> do
unless (visible a && visible b) $ failure $ text "because its two final arguments are not both visible."
case unEl core of
Sort{} -> return ()
Con{} -> __IMPOSSIBLE__
Level{} -> __IMPOSSIBLE__
Lam{} -> __IMPOSSIBLE__
Pi{} -> __IMPOSSIBLE__
_ -> failure $ text "because its type does not end in a sort, but in "
<+> do inTopContext $ addContext tel $ prettyTCM core
data RelView = RelView
{ relViewTel :: Telescope
, relViewDelta :: ListTel
, relViewType :: Dom Type
, relViewType' :: Dom Type
, relViewCore :: Type
}
relView :: Type -> TCM (Maybe RelView)
relView t = do
TelV tel core <- telView t
let n = size tel
(delta, lastTwo) = splitAt (n - 2) $ telToList tel
if size lastTwo < 2 then return Nothing else do
let [a, b] = fmap snd <$> lastTwo
return $ Just $ RelView tel delta a b core
addRewriteRule :: QName -> TCM ()
addRewriteRule q = do
requireOptionRewriting
let failNoBuiltin = typeError $ GenericError $
"Cannot add rewrite rule without prior BUILTIN REWRITE"
rel <- fromMaybeM failNoBuiltin $ getBuiltinName builtinRewrite
def <- instantiateDef =<< getConstInfo q
when (isEmptyFunction $ theDef def) $
typeError . GenericDocError =<< hsep
[ text "Rewrite rule from function "
, prettyTCM q
, text " cannot be added before the function definition"
]
relV <- relView =<< do defType <$> getConstInfo rel
let RelView _tel delta a _a' _core =
fromMaybe __IMPOSSIBLE__ relV
reportSDoc "rewriting" 30 $ do
text "rewrite relation at type " <+> do
inTopContext $ prettyTCM (telFromList delta) <+> text " |- " <+> do
addContext delta $ prettyTCM a
TelV gamma1 core <- telView $ defType def
reportSDoc "rewriting" 30 $ do
text "attempting to add rewrite rule of type " <+> do
prettyTCM gamma1 <+> text " |- " <+> do
addContext gamma1 $ prettyTCM core
let failureWrongTarget = typeError . GenericDocError =<< hsep
[ prettyTCM q , text " does not target rewrite relation" ]
let failureMetas = typeError . GenericDocError =<< hsep
[ prettyTCM q , text " is not a legal rewrite rule, since it contains unsolved meta variables" ]
let failureNotDefOrCon = typeError . GenericDocError =<< hsep
[ prettyTCM q , text " is not a legal rewrite rule, since the left-hand side is neither a defined symbol nor a constructor" ]
let failureFreeVars xs = typeError . GenericDocError =<< hsep
[ prettyTCM q , text " is not a legal rewrite rule, since the following variables are not bound by the left hand side: " , prettyList_ (map (prettyTCM . var) $ IntSet.toList xs) ]
let failureIllegalRule = typeError . GenericDocError =<< hsep
[ prettyTCM q , text " is not a legal rewrite rule" ]
case unEl core of
Def rel' es@(_:_:_) | rel == rel' -> do
let vs = map unArg $ fromMaybe __IMPOSSIBLE__ $ allApplyElims es
n = size vs
(us, [lhs, rhs]) = splitAt (n - 2) vs
unless (size delta == size us) __IMPOSSIBLE__
b <- instantiateFull $ applySubst (parallelS $ reverse us) a
gamma0 <- getContextTelescope
gamma1 <- instantiateFull gamma1
let gamma = gamma0 `abstract` gamma1
unless (null $ allMetas (telToList gamma1)) $ do
reportSDoc "rewriting" 30 $ text "metas in gamma1: " <+> text (show $ allMetas $ telToList gamma1)
failureMetas
lhs <- modifyAllowedReductions (const [InlineReductions]) $ normalise lhs
(f , hd , es) <- case lhs of
Def f es -> return (f , Def f , es)
Con c ci vs -> do
let hd = Con c ci
return (conName c , hd , vs)
_ -> failureNotDefOrCon
ifNotAlreadyAdded f $ do
rew <- addContext gamma1 $ do
es <- etaContract =<< normalise es
checkNoLhsReduction f (hd es)
rhs <- etaContract =<< normalise rhs
unless (null $ allMetas (es, rhs, b)) $ do
reportSDoc "rewriting" 30 $ text "metas in lhs: " <+> text (show $ allMetas es)
reportSDoc "rewriting" 30 $ text "metas in rhs: " <+> text (show $ allMetas rhs)
reportSDoc "rewriting" 30 $ text "metas in b : " <+> text (show $ allMetas b)
failureMetas
ps <- patternFrom Relevant 0 es
reportSDoc "rewriting" 30 $
text "Pattern generated from lhs: " <+> prettyTCM (PDef f ps)
let freeVars = usedArgs (defArgOccurrences def) `IntSet.union` allFreeVars (ps,rhs)
boundVars = nlPatVars ps
reportSDoc "rewriting" 40 $
text "variables bound by the pattern: " <+> text (show boundVars)
reportSDoc "rewriting" 40 $
text "variables free in the rewrite rule: " <+> text (show freeVars)
unlessNull (freeVars IntSet.\\ boundVars) failureFreeVars
return $ RewriteRule q gamma f ps rhs (unDom b)
reportSDoc "rewriting" 10 $
text "considering rewrite rule " <+> prettyTCM rew
reportSDoc "rewriting" 60 $
text "considering rewrite rule" <+> text (show rew)
addRewriteRules f [rew]
_ -> failureWrongTarget
where
checkNoLhsReduction :: QName -> Term -> TCM ()
checkNoLhsReduction f v = do
v' <- normalise v
unless (v == v') $ do
reportSDoc "rewriting" 20 $ text "v = " <+> text (show v)
reportSDoc "rewriting" 20 $ text "v' = " <+> text (show v')
typeError . GenericDocError =<< fsep
[ prettyTCM q <+> text " is not a legal rewrite rule, since the left-hand side "
, prettyTCM v <+> text " reduces to " <+> prettyTCM v' ]
ifNotAlreadyAdded :: QName -> TCM () -> TCM ()
ifNotAlreadyAdded f cont = do
rews <- getRewriteRulesFor f
if any ((q ==) . rewName) rews then
genericWarning =<< do
text "Rewrite rule " <+> prettyTCM q <+> text " has already been added"
else cont
usedArgs :: [Pos.Occurrence] -> IntSet
usedArgs occs = IntSet.fromList $ map snd $ usedIxs
where
allIxs = zip occs $ downFrom $ size occs
usedIxs = filter (used . fst) allIxs
used Pos.Unused = False
used _ = True
addRewriteRules :: QName -> RewriteRules -> TCM ()
addRewriteRules f rews = do
reportSDoc "rewriting" 10 $ text "rewrite rule ok, adding it to the definition of " <+> prettyTCM f
let matchables = getMatchables rews
reportSDoc "rewriting" 30 $ text "matchable symbols: " <+> prettyTCM matchables
modifySignature $ addRewriteRulesFor f rews matchables
rewriteWith :: Maybe Type
-> Term
-> RewriteRule
-> Elims
-> ReduceM (Either (Blocked Term) Term)
rewriteWith mt v rew@(RewriteRule q gamma _ ps rhs b) es = do
traceSDoc "rewriting" 75 (sep
[ text "attempting to rewrite term " <+> prettyTCM (v `applyE` es)
, text " with rule " <+> prettyTCM rew
]) $ do
result <- nonLinMatch gamma ps es
case result of
Left block -> return $ Left $ block $> v `applyE` es
Right sub -> do
let v' = applySubst sub rhs
traceSDoc "rewriting" 70 (sep
[ text "rewrote " <+> prettyTCM (v `applyE` es)
, text " to " <+> prettyTCM v'
]) $ do
return $ Right v'
rewrite :: Blocked_ -> Term -> RewriteRules -> Elims -> ReduceM (Reduced (Blocked Term) Term)
rewrite block v rules es = do
rewritingAllowed <- optRewriting <$> pragmaOptions
if (rewritingAllowed && not (null rules)) then
loop block rules =<< instantiateFull' es
else
return $ NoReduction (block $> v `applyE` es)
where
loop :: Blocked_ -> RewriteRules -> Elims -> ReduceM (Reduced (Blocked Term) Term)
loop block [] es = return $ NoReduction $ block $> v `applyE` es
loop block (rew:rews) es
| let n = rewArity rew, length es >= n = do
let (es1, es2) = List.genericSplitAt n es
result <- rewriteWith Nothing v rew es1
case result of
Left (Blocked m u) -> loop (block `mappend` Blocked m ()) rews es
Left (NotBlocked _ _) -> loop block rews es
Right w -> return $ YesReduction YesSimplification $ w `applyE` es2
| otherwise = loop (block `mappend` NotBlocked Underapplied ()) rews es
class NLPatVars a where
nlPatVarsUnder :: Int -> a -> IntSet
nlPatVars :: a -> IntSet
nlPatVars = nlPatVarsUnder 0
instance (Foldable f, NLPatVars a) => NLPatVars (f a) where
nlPatVarsUnder k = foldMap $ nlPatVarsUnder k
instance NLPatVars NLPType where
nlPatVarsUnder k (NLPType l a) = nlPatVarsUnder k l `IntSet.union` nlPatVarsUnder k a
instance NLPatVars NLPat where
nlPatVarsUnder k p =
case p of
PVar i _ -> singleton $ i - k
PDef _ es -> nlPatVarsUnder k es
PWild -> empty
PLam _ p' -> nlPatVarsUnder (k+1) $ unAbs p'
PPi a b -> nlPatVarsUnder k a `IntSet.union` nlPatVarsUnder (k+1) (unAbs b)
PBoundVar _ es -> nlPatVarsUnder k es
PTerm{} -> empty
rewArity :: RewriteRule -> Int
rewArity = length . rewPats
class GetMatchables a where
getMatchables :: a -> [QName]
instance (Foldable f, GetMatchables a) => GetMatchables (f a) where
getMatchables = foldMap getMatchables
instance GetMatchables NLPat where
getMatchables p =
case p of
PVar _ _ -> empty
PWild -> empty
PDef f _ -> singleton f
PLam _ x -> empty
PPi a b -> empty
PBoundVar i es -> empty
PTerm _ -> empty
instance GetMatchables RewriteRule where
getMatchables = getMatchables . rewPats
instance Free NLPat where
freeVars' p = case p of
PVar _ _ -> mempty
PWild -> mempty
PDef _ es -> freeVars' es
PLam _ u -> freeVars' u
PPi a b -> freeVars' (a,b)
PBoundVar _ es -> freeVars' es
PTerm t -> freeVars' t
instance Free NLPType where
freeVars' (NLPType l a) =
ifM ((IgnoreNot ==) <$> asks feIgnoreSorts)
(freeVars' (l, a))
(freeVars' a)