buildwrapper-0.7.3: src/Language/Haskell/BuildWrapper/GHCStorage.hs
{-# LANGUAGE CPP,OverloadedStrings,PatternGuards #-}
-- |
-- Module : Language.Haskell.BuildWrapper.GHCStorage
-- Copyright : (c) JP Moresmau 2012
-- License : BSD3
--
-- Maintainer : jpmoresmau@gmail.com
-- Stability : beta
-- Portability : portable
--
-- Store to disk in JSON format the results of the GHC AST build, and the build flags
-- this helps us with performance (we only call GHC when the file has changed, not everytime we want to find what's at a given source point
module Language.Haskell.BuildWrapper.GHCStorage where
import Language.Haskell.BuildWrapper.Base
import Data.Generics
import System.Directory
import System.FilePath
import PprTyThing
import GHC
import Outputable
import Bag(Bag,bagToList)
import Var(Var,varType,varName)
import FastString(FastString)
import NameSet(NameSet)
import Name hiding (varName)
import DataCon (dataConName)
#if __GLASGOW_HASKELL__ < 700
import GHC.SYB.Instances
#endif
#if __GLASGOW_HASKELL__ < 702
import TypeRep (Type(..), PredType(..))
import VarSet
#elif __GLASGOW_HASKELL__ < 704
import TypeRep (Type(..), Pred(..), tyVarsOfType)
import VarSet (isEmptyVarSet)
#else
import TypeRep (Type(..), tyVarsOfType)
import VarSet (isEmptyVarSet)
#endif
#if __GLASGOW_HASKELL__ >= 704
import TcEvidence
#endif
import qualified Data.ByteString.Lazy as BS
-- import qualified Data.ByteString.Lazy.Char8 as BSC (putStrLn)
import qualified Data.ByteString as BSS
import Data.Aeson
import Data.Maybe
import qualified Data.Text as T
import qualified Data.HashMap.Lazy as HM
import qualified Data.Map as DM
import qualified Data.Vector as V
import Data.Attoparsec.Number (Number(I))
#if __GLASGOW_HASKELL__ < 706
import System.Time (ClockTime)
#else
import Data.Time.Clock (UTCTime)
#endif
import Type (splitFunTys)
import Unique (getUnique)
import Data.List (sortBy)
-- import GHC.SYB.Utils (Stage(..), showData)
-- | get the file storing the information for the given source file
getInfoFile :: FilePath -- ^ the source file
-> FilePath
getInfoFile fp= let
(dir,file)=splitFileName fp
in combine dir ('.' : addExtension file ".bwinfo")
-- | get the file storing the information for the given source file
getUsageFile :: FilePath -- ^ the source file
-> FilePath
getUsageFile fp= let
(dir,file)=splitFileName fp
in combine dir ('.' : addExtension file ".bwusage")
-- | remove the storage file
clearInfo :: FilePath -- ^ the source file
-> IO()
clearInfo fp =do
let ghcInfoFile=getInfoFile fp
removeFile ghcInfoFile
-- | store the build flags
storeBuildFlagsInfo :: FilePath -- ^ the source file
-> (BuildFlags,[BWNote]) -- ^ build flags and notes
-> IO()
storeBuildFlagsInfo fp bf=setStoredInfo fp "BuildFlags" (toJSON bf)
-- | generate the JSON from the typechecked module
-- this incorporates info from the renamed source with types annotations from the typechecked source
generateGHCInfo :: DynFlags -> TypecheckedModule -> Value
generateGHCInfo df tcm=let
-- extract usages from typechecked source
tcvals=extractUsages $ dataToJSON df $ typecheckedSource tcm
-- store objects with type annotations in a map keyed by module, name, line and column
tcByNameLoc=foldr buildMap DM.empty tcvals
-- extract usages from renamed source
rnvals=extractUsages $ dataToJSON df $ tm_renamed_source tcm
-- add type information on objects
typedVals=map (addType tcByNameLoc) rnvals
in (Array $ V.fromList typedVals)
where
buildMap v@(Object m) dm |
Just pos<-HM.lookup "Pos" m,
Success ifs <- fromJSON pos,
Just (String s)<-HM.lookup "Name" m,
Just (String mo)<-HM.lookup "Module" m,
Just _<-HM.lookup "QType" m,
Just _<-HM.lookup "Type" m,
Just "v"<-HM.lookup "HType" m,
Just _<-HM.lookup "GType" m=
DM.insert (mo,s,iflLine $ ifsStart ifs,0) v $ -- add column 0 for some cases where the spans are funny
DM.insert (mo,s,iflLine $ ifsStart ifs,iflColumn $ ifsStart ifs) v dm
buildMap _ dm=dm
addType dm v@(Object m1) |
Just pos<-HM.lookup "Pos" m1,
Success ifs <- fromJSON pos,
Just (String s)<-HM.lookup "Name" m1,
Just (String mo)<-HM.lookup "Module" m1,
Just "v"<-HM.lookup "HType" m1=let
mv=DM.lookup (mo,s,iflLine $ ifsStart ifs,iflColumn $ ifsStart ifs) dm
mv2=case mv of
Nothing -> DM.lookup (mo,s,iflLine $ ifsStart ifs,0) dm
a->a
in case mv2 of
Just (Object m2) |
Just qt<-HM.lookup "QType" m2,
Just t<-HM.lookup "Type" m2,
Just gt<-HM.lookup "GType" m2 -> Object (HM.insert "QType" qt $
HM.insert "Type" t $
HM.insert "GType" gt
m1)
_ -> v
addType _ v=v
-- | store the GHC generated AST
storeGHCInfo ::
DynFlags
-> FilePath -- ^ the source file
-> TypecheckedModule -- ^ the GHC AST
-> IO()
storeGHCInfo df fp tcm= -- do
-- putStrLn $ showData TypeChecker 4 $ typecheckedSource tcm
-- putStrLn "Typechecked"
-- BSC.putStrLn $ encode $ dataToJSON $ typecheckedSource tcm
-- putStrLn "Renamed"
-- BSC.putStrLn $ encode $ dataToJSON $ tm_renamed_source tcm
-- let tcvals=extractUsages $ dataToJSON $ typecheckedSource tcm
-- BSC.putStrLn $ encode $ Array $ V.fromList tcvals
-- let rnvals=extractUsages $ dataToJSON $ tm_renamed_source tcm
-- BSC.putStrLn $ encode $ Array $ V.fromList rnvals
setStoredInfo fp "AST" $ generateGHCInfo df tcm
-- | read the GHC AST as a JSON value
readGHCInfo :: FilePath -- ^ the source file
-> IO(Maybe Value)
readGHCInfo fp=do
(Object hm)<-readStoredInfo fp
return $ HM.lookup "AST" hm
-- | read the build flags and notes as a JSON value
readBuildFlagsInfo :: FilePath -- ^ the source file
#if __GLASGOW_HASKELL__ < 706
-> ClockTime -- ^ time the cabal file was changed. If the file was changed after the storage file, we return Nothing
#else
-> UTCTime
#endif
-> IO (Maybe (BuildFlags,[BWNote]))
readBuildFlagsInfo fp ct=do
let ghcInfoFile=getInfoFile fp
ex<-doesFileExist ghcInfoFile
if ex then do
ctF<-getModificationTime ghcInfoFile
if ctF>ct
then do
(Object hm)<-readStoredInfo fp
return $ maybe Nothing (\x-> case fromJSON x of
Success a->Just a
Error _->Nothing) $ HM.lookup "BuildFlags" hm
else return Nothing
else return Nothing
-- | utility function to store the given value under the given key
setStoredInfo :: FilePath -- ^ the source file
-> T.Text -- ^ the key under which the value will be put
-> Value -- ^ the value
-> IO()
setStoredInfo fp k v=do
let ghcInfoFile=getInfoFile fp
(Object hm)<-readStoredInfo fp
let hm2=HM.insert k v hm
BSS.writeFile ghcInfoFile $ BSS.concat $ BS.toChunks $ encode $ Object hm2
-- | read the top JSON value containing all the information
readStoredInfo :: FilePath -- ^ the source file
-> IO Value
readStoredInfo fp=do
let ghcInfoFile=getInfoFile fp
ex<-doesFileExist ghcInfoFile
mv<-if ex
then do
bs<-BSS.readFile ghcInfoFile
return $ decode' $ BS.fromChunks [bs]
else return Nothing
return $ fromMaybe (object []) mv
-- | write the usage info file
setUsageInfo :: FilePath -- ^ the source file
-> Value -- ^ the value
-> IO()
setUsageInfo fp v=do
let usageFile=getUsageFile fp
BSS.writeFile usageFile $ BSS.concat $ BS.toChunks $ encode v
-- | read the usage info file
getUsageInfo :: FilePath -- ^ the source file
-> IO Value
getUsageInfo fp=do
let usageFile=getUsageFile fp
ex<-doesFileExist usageFile
mv<-if ex
then do
bs<-BSS.readFile usageFile
return $ decode' $ BS.fromChunks [bs]
else return Nothing
return $ fromMaybe (object []) mv
-- | convert a Data into a JSON value, with specific treatment for interesting GHC AST objects, and avoiding the holes
dataToJSON :: Data a => DynFlags -> a -> Value
dataToJSON df =
generic `ext1Q` list `extQ` string `extQ` fastString `extQ` srcSpanToJSON
`extQ` name `extQ` ocName `extQ` modName `extQ` var `extQ` exprVar `extQ` dataCon
`extQ` bagName `extQ` bagRdrName `extQ` bagVar `extQ` nameSet
`extQ` postTcType `extQ` fixity `extQ` hsBind
where generic :: Data a => a -> Value
generic t =arr $ gmapQ (dataToJSON df) t
-- object [(T.pack $ showConstr (toConstr t)) .= sub ]
string = Data.Aeson.String . T.pack :: String -> Value
fastString:: FastString -> Value
fastString fs= object ["FastString" .= T.pack (show fs)]
list l = arr $ map (dataToJSON df) l
arr a = let
sub=filter (/= Null) a
in case sub of
[] -> Null
[x] -> x
_ -> toJSON sub
name :: Name -> Value
name n = object (nameAndModule n ++["GType" .= string "Name","HType".= string (if isValOcc (nameOccName n) then "v" else "t")])
ocName :: OccName -> Value
ocName o = name (mkSystemName (getUnique o) o)
--object ["Name" .= string (OccName.occNameString o),"HType" .= string (if isValOcc o then "v" else "t")]
modName :: ModuleName -> Value
modName m= object [ "Name" .= string (showSD True df $ ppr m),"GType" .= string "ModuleName","HType" .= string "m"]
var :: Var -> Value
var v = typedVar v (varType v)
dataCon :: DataCon -> Value
dataCon d = let
t=dataConUserType d
in object (nameAndModule (dataConName d) ++ typeToJSON t ++ [
"GType" .= string "DataCon",
"HType" .= string "v"])
-- simple:: T.Text -> String -> Value
-- simple nm v=object [nm .= T.pack v]
simpleV:: T.Text -> Value -> Value
simpleV nm v=object [nm .= v]
bagRdrName:: Bag (Located (HsBind RdrName)) -> Value
bagRdrName = simpleV "Bag(Located (HsBind RdrName))" . list . bagToList
bagName :: Bag (Located (HsBind Name)) -> Value
bagName = simpleV "Bag(Located (HsBind Name))" . list . bagToList
bagVar :: Bag (Located (HsBind Var)) -> Value
bagVar = simpleV "Bag(Located (HsBind Var))". list . bagToList
exprVar :: HsExpr Var -> Value
exprVar ev = let
mt=typeOfExpr ev
in case mt of
Just (t,v)-> typedVar v t
Nothing->generic ev
typedVar :: Var -> Type -> Value
typedVar v t=object (nameAndModule (varName v) ++ typeToJSON t ++
["GType" .= string "Var",
"HType" .= string (if isValOcc (nameOccName (Var.varName v)) then "v" else "t")])
nameSet = const $ Data.Aeson.String "{!NameSet placeholder here!}" :: NameSet -> Value
postTcType = const Null :: Type -> Value -- string . showSDoc . ppr
fixity = const Null :: GHC.Fixity -> Value --simple "Fixity" . showSDoc . ppr
typeToJSON :: Type -> [(T.Text,Value)]
typeToJSON t = -- let
--appT=let (a,b)= splitAppTys t in (a:b)
--allT2=concatMap typesInsideType appT
-- allT=typesInsideType t
-- allT2=allT ++ concatMap (\t2->let (a,b)= splitAppTys t2 in (a:b)) allT
-- in
["Type" .= string (showSD False df $ pprTypeForUser True t),
"QType" .= string (showSD True df $ pprTypeForUser True t)]
-- ,"AllTypes" .= (map string $ filter ("[]" /=) $ nubOrd $ map (showSDoc . withPprStyle (mkUserStyle ((\_ _ -> NameNotInScope2), const True) AllTheWay) . pprTypeForUser True) allT2)]
hsBind :: HsBindLR Name Name -> Value
--(arr [dataToJSON $ getLoc fid,dataToJSON $ unLoc fid]) :
hsBind (FunBind fid _ (MatchGroup matches _) _ _ _) =arr $ map (\m->arr [arr [dataToJSON df $ getLoc m,dataToJSON df $ unLoc fid],dataToJSON df m]) matches
hsBind a=generic a
-- nameAndModule :: Name -> [Pair]
nameAndModule n=let
mm=nameModule_maybe n
mn=maybe "" (showSD True df . ppr . moduleName) mm
pkg=maybe "" (showSD True df . ppr . modulePackageId) mm
na=showSD False df $ ppr n
in ["Module" .= string mn,"Package" .= string pkg, "Name" .= string na]
showSD :: Bool
-> DynFlags
-> SDoc
-> String
#if __GLASGOW_HASKELL__ < 706
showSD True _ =showSDoc
showSD False _ =showSDocUnqual
#else
showSD True df =showSDoc df
showSD False df =showSDocUnqual df
#endif
showSDUser :: PrintUnqualified
-> DynFlags
-> SDoc
-> String
#if __GLASGOW_HASKELL__ < 706
showSDUser unqual _ =showSDocForUser unqual
#else
showSDUser unqual df =showSDocForUser df unqual
#endif
showSDDump :: DynFlags
-> SDoc
-> String
#if __GLASGOW_HASKELL__ < 706
showSDDump _ =showSDocDump
#else
showSDDump df =showSDocDump df
#endif
srcSpanToJSON :: SrcSpan -> Value
srcSpanToJSON src
| isGoodSrcSpan src = object[ "SrcSpan" .= toJSON [srcLocToJSON $ srcSpanStart src, srcLocToJSON $ srcSpanEnd src]]
| otherwise = Null
#if __GLASGOW_HASKELL__ < 702
srcLocToJSON :: SrcLoc -> Value
srcLocToJSON sl
| isGoodSrcLoc sl=object ["line" .= toJSON (srcLocLine sl),"column" .= toJSON (srcLocCol sl)]
| otherwise = Null
#else
srcLocToJSON :: SrcLoc -> Value
srcLocToJSON (RealSrcLoc sl)=object ["line" .= toJSON (srcLocLine sl),"column" .= toJSON (srcLocCol sl)]
srcLocToJSON _ = Null
#endif
typesInsideType :: Type -> [Type]
typesInsideType t=let
(f1,f2)=splitFunTys t
in f2 : concatMap typesInsideType f1
---- | debug function: shows on standard output the JSON representation of the given data
--debugToJSON :: Data a =>a -> IO()
--debugToJSON = BSC.putStrLn . encode . dataToJSON
--
---- | debug searching thing at point in given data
--debugFindInJSON :: Data a => Int -> Int -> a -> IO()
--debugFindInJSON l c a= do
-- let v=dataToJSON a
-- let mv=findInJSON (overlap l c) v
-- case mv of
-- Just rv->do
-- putStrLn "something found!"
-- BSC.putStrLn $ encode rv
-- Nothing->putStrLn "nothing found!"
-- | simple type for search function
type FindFunc= Value -> Bool
-- | find in JSON AST and return the string result
findInJSONFormatted :: Bool -- ^ should the output be qualified?
-> Bool -- ^ should the output be fully typed?
-> Maybe Value -- ^ result of search
-> String
findInJSONFormatted qual typed (Just (Object m)) | Just (String name)<-HM.lookup "Name" m=let
tn=T.unpack name
qn=if qual
then
let mo=maybe "" addDot $ HM.lookup "Module" m
in mo ++ tn
else tn
in if typed then
let mt=HM.lookup (if qual then "QType" else "Type") m
in case mt of
Just (String t)->qn ++ " :: " ++ T.unpack t
_ -> tn
else
let mt=HM.lookup "HType" m
in case mt of
Just (String t)->qn ++ " " ++ T.unpack t
_ -> tn
where
addDot :: Value -> String
addDot (String s)=T.unpack s ++ "."
addDot _=error "expected String value for Module key"
findInJSONFormatted _ _ _="no info"
findInJSONData :: Maybe Value -> Maybe ThingAtPoint
findInJSONData (Just o@(Object m)) | Just (String _)<-HM.lookup "Name" m=case fromJSON o of
Success tap->tap
Error _ -> Nothing
findInJSONData _=Nothing
---- | find in JSON AST
--findInJSON :: FindFunc -- ^ the evaluation function
-- -> Value -- ^ the root object containing the AST
-- -> Maybe Value
--findInJSON f (Array arr) | not $ V.null arr=let
-- v1=arr V.! 0
-- in if f v1 && V.length arr==2 -- we have an array of two elements, the first one being a matching SrcSpan we go down the second element
-- then
-- let
-- mv=findInJSON f $ arr V.! 1
-- in case mv of
-- Just rv-> Just rv -- found something underneath
-- Nothing -> Just $ arr V.! 1 -- found nothing underneath, return second element of the array
-- else
-- let rvs=catMaybes $ V.toList $ fmap (findInJSON f) arr -- other case of arrays: check on each element
-- in case rvs of
-- (x:_)->Just x -- return first match
-- []->Nothing
--findInJSON f (Object obj)=let rvs=mapMaybe (findInJSON f) $ HM.elems obj -- in a complex object: check on contained elements
-- in case rvs of
-- (x:_)->Just x
-- []->Nothing
--findInJSON _ _= Nothing
--
---- | overlap function: find whatever is at the given line and column
--overlap :: Int -- ^ line
-- -> Int -- ^ column
-- -> FindFunc
--overlap l c (Object m) |
-- Just pos<-HM.lookup "SrcSpan" m,
-- Just (l1,c1,l2,c2)<-extractSourceSpan pos=l1<=l && c1<=c && l2>=l && c2>=c
--overlap _ _ _=False
-- | find in JSON AST
findInJSON :: FindFunc -- ^ the evaluation function
-> Value -- ^ the root object containing the AST
-> Maybe Value
findInJSON f (Array vals)=listToMaybe $ sortBy lastPos $ filter f $ V.toList vals
findInJSON _ _=Nothing
-- | find in JSON AST
findAllInJSON :: FindFunc -- ^ the evaluation function
-> Value -- ^ the root object containing the AST
-> [Value]
findAllInJSON f (Array vals)=filter f $ V.toList vals
findAllInJSON _ _=[]
-- | sort Value by position, descending
lastPos :: Value -> Value -> Ordering
lastPos (Object m1) (Object m2) |
Just pos1<-HM.lookup "Pos" m1,
Success ifs1 <- fromJSON pos1,
Just pos2<-HM.lookup "Pos" m2,
Success ifs2 <- fromJSON pos2 =let
c1=compare (iflLine $ ifsStart ifs2) (iflLine $ ifsStart ifs1)
in case c1 of
EQ -> compare (iflColumn $ ifsStart ifs2) (iflColumn $ ifsStart ifs1)
a -> a
lastPos _ _=EQ
-- | overlap function: find whatever is at the given line and column
overlap :: Int -- ^ line
-> Int -- ^ column
-> FindFunc
overlap l c (Object m) |
Just pos<-HM.lookup "Pos" m,
Success ifs <- fromJSON pos=iflOverlap ifs (InFileLoc l c)
overlap _ _ _=False
-- | contains function: find whatever is contained inside the given span
contains :: Int -- ^ start line
-> Int -- ^ start column
-> Int -- ^ end line
-> Int -- ^ end column
-> FindFunc
contains sl sc el ec (Object m) |
Just pos<-HM.lookup "Pos" m,
Success ifs <- fromJSON pos=iflOverlap (InFileSpan (InFileLoc sl sc) (InFileLoc el ec)) (ifsStart ifs)
contains _ _ _ _ _=False
-- | isGHCType function: find whatever has the proper GHCType
isGHCType :: String -- ^ the type
-> FindFunc
isGHCType tp (Object m) |
Just pos<-HM.lookup "GType" m,
Success ghcType <- fromJSON pos=tp == ghcType
isGHCType _ _ =False
extractUsages :: Value -- ^ the root object containing the AST
-> [Value]
extractUsages (Array arr) | not $ V.null arr=let
v1=arr V.! 0
msrc=extractSource v1
in if isJust msrc && V.length arr==2 -- we have an array of two elements, the first one being a matching SrcSpan we go down the second element
then extractName v1 (arr V.! 1) ++ extractUsages (arr V.! 1)
else concat $ V.toList $ fmap extractUsages arr -- other case of arrays: check on each element
extractUsages (Object obj)=concatMap extractUsages $ HM.elems obj -- in a complex object: check on contained elements
-- (extractName o) :
extractUsages _= []
extractName :: Value -> Value -> [Value]
extractName src (Object m) |
Just ifl<-extractSource src,
Just (String s)<-HM.lookup "Name" m,
Just (String mo)<-HM.lookup "Module" m,
-- not $ T.null mo, -- keep local objects
Just (String p)<-HM.lookup "Package" m,
mqt<-HM.lookup "QType" m,
mst<-HM.lookup "Type" m,
mgt<-HM.lookup "GType" m,
Just (String t)<-HM.lookup "HType" m,
at<-fromMaybe (Array V.empty) $ HM.lookup "AllTypes" m
=let
atts=["Name" .= s,"Module" .= mo,"Package" .= p,"HType" .= t,"AllTypes" .= at, "Pos" .= toJSON ifl, "QType" .= mqt, "Type" .= mst,"GType" .= mgt]
--atts1=if T.null mo
-- then atts
-- else ():atts
in [object atts]
extractName _ _=[]
extractSource :: Value -> Maybe InFileSpan
extractSource (Object m) |
Just pos<-HM.lookup "SrcSpan" m,
Just (sl,sc,el,ec)<-extractSourceSpan pos=Just $ InFileSpan (InFileLoc sl sc) (InFileLoc el ec)
extractSource _=Nothing
-- | extract the source span from JSON
extractSourceSpan :: Value -> Maybe (Int,Int,Int,Int)
extractSourceSpan (Array arr) | V.length arr==2 = do
let v1=arr V.! 0
let v2=arr V.! 1
(l1,c1)<-extractSourceLoc v1
(l2,c2)<-extractSourceLoc v2
return (l1,c1,l2,c2)
extractSourceSpan _ =Nothing
-- | extract the source location from JSON
extractSourceLoc :: Value -> Maybe (Int,Int)
extractSourceLoc (Object m) |
Just (Number(I l))<-HM.lookup "line" m,
Just (Number(I c))<-HM.lookup "column" m=Just (fromIntegral l,fromIntegral c)
extractSourceLoc _ = Nothing
-- | resolve the type of an expression
typeOfExpr :: HsExpr Var -> Maybe (Type,Var)
typeOfExpr (HsWrap wr (HsVar ident)) =
let -- Unwrap a HsWrapper and its associated type
unwrap WpHole t = t
unwrap (WpCompose w1 w2) t = unwrap w1 (unwrap w2 t)
unwrap (WpCast _) t = t -- XXX: really?
unwrap (WpTyApp t') t = AppTy t t'
unwrap (WpTyLam tv) t = ForAllTy tv t
-- do something else with coercion/dict vars?
#if __GLASGOW_HASKELL__ < 700
unwrap (WpApp v) t = AppTy t (TyVarTy v)
unwrap (WpLam v) t = ForAllTy v t
#else
-- unwrap (WpEvApp v) t = AppTy t (TyVarTy v)
unwrap (WpEvLam v) t = ForAllTy v t
unwrap (WpEvApp _) t = t
#endif
unwrap (WpLet _) t = t
#ifdef WPINLINE
unwrap WpInline t = t
#endif
in Just (reduceType $ unwrap wr (varType ident), ident)
-- All other search results produce no type information
typeOfExpr _ = Nothing
-- | Reduce type-level applications by pushing 'AppTy' arguments on a stack and binding them in an environment at the
-- appropriate 'ForAllTy'. Class constraints that have no free variables after reduction are removed.
reduceType :: Type -> Type
reduceType = reduce [] []
where reduce :: [Type] -> [(Var,Type)] -> Type -> Type
-- The stack is only passed into AppTy and ForallTy cases, since otherwise it will be empty anyway.
-- We probably don't even need to reduce in the other cases, but it won't cause any problems and keeps this
-- function simpler (we do need to substitute).
-- NOTE: when working on this code, make sure to temporarily disable caching in GHC.withJSONAST.
reduce _ env t@(TyVarTy var) | Just arg <- lookup var env = arg -- note: var's are unique
| otherwise = t
reduce _ env (TyConApp tycon kts) = TyConApp tycon $ map (reduce [] env) kts
reduce stck env (AppTy typ1 typ2) = reduce (reduce [] env typ2 : stck) env typ1 -- push argument onto stack
reduce [] env (ForAllTy var typ) = ForAllTy var $ reduce [] env typ
reduce (arg:stck) env (ForAllTy var typ) = reduce stck ((var,arg) : env) typ -- bind argument from stack to var
#if __GLASGOW_HASKELL__ > 704
reduce _ _ t@(LitTy _) = t
#endif
reduce _ env (FunTy typ1 typ2) =
let rtyp1 = reduce [] env typ1
rtyp2 = reduce [] env typ2
in case typ1 of
-- remove class constraints without free variables to prevent things like (Ord Char => Char)
#if __GLASGOW_HASKELL__ < 704
PredTy _ | isEmptyVarSet (tyVarsOfType rtyp1) -> rtyp2
#else
TyConApp tycon _ | isClassTyCon tycon && isEmptyVarSet (tyVarsOfType rtyp1) -> rtyp2
#endif
_ -> FunTy rtyp1 rtyp2
#if __GLASGOW_HASKELL__ < 704
-- before ghc 7.4, constraints were encoded with a PredTy constructor
reduce _ env (PredTy pt) = PredTy $ reducePredType pt
where reducePredType (ClassP c ts) = ClassP c $ map (reduce [] env) ts
reducePredType (IParam i t) = IParam i (reduce [] env t)
reducePredType (EqPred t1 t2) = EqPred (reduce [] env t1) (reduce [] env t2)
#if __GLASGOW_HASKELL__ < 702
-- before ghc 7.2, tyVarsOfType was not defined. The code below comes from the ghc-7.2.2 version of TypeRep.hs.
tyVarsOfType :: Type -> VarSet
-- ^ NB: for type synonyms tyVarsOfType does /not/ expand the synonym
tyVarsOfType (TyVarTy v) = unitVarSet v
tyVarsOfType (TyConApp _ tys) = tyVarsOfTypes tys
tyVarsOfType (PredTy sty) = varsOfPred tyVarsOfType sty
tyVarsOfType (FunTy arg res) = tyVarsOfType arg `unionVarSet` tyVarsOfType res
tyVarsOfType (AppTy fun arg) = tyVarsOfType fun `unionVarSet` tyVarsOfType arg
tyVarsOfType (ForAllTy tyvar ty) = delVarSet (tyVarsOfType ty) tyvar
tyVarsOfTypes :: [Type] -> TyVarSet
tyVarsOfTypes tys = foldr (unionVarSet . tyVarsOfType) emptyVarSet tys
varsOfPred :: (Type -> VarSet) -> PredType -> VarSet
varsOfPred f (IParam _ ty) = f ty
varsOfPred f (ClassP _ tys) = foldr (unionVarSet . f) emptyVarSet tys
varsOfPred f (EqPred ty1 ty2) = f ty1 `unionVarSet` f ty2
#endif
#endif