ghc-mod/Language/Haskell/GhcMod/CaseSplit.hs

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{-# LANGUAGE CPP #-}
module Language.Haskell.GhcMod.CaseSplit (
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splits
) where
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import CoreMonad (liftIO)
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import Data.Function (on)
import Data.List (find, intercalate, sortBy)
import Data.Maybe (isJust)
import qualified Data.Text as T
import qualified Data.Text.IO as T (readFile)
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import qualified DataCon as Ty
import Exception (ghandle, SomeException(..))
import GHC (GhcMonad, LPat, Id, ParsedModule(..), TypecheckedModule(..), DynFlags, SrcSpan, Type, GenLocated(L))
import qualified GHC as G
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import Language.Haskell.GhcMod.Convert
import qualified Language.Haskell.GhcMod.Gap as Gap
import Language.Haskell.GhcMod.Monad
import Language.Haskell.GhcMod.SrcUtils
import Outputable (ppr, PprStyle)
import qualified TyCon as Ty
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import qualified Type as Ty
----------------------------------------------------------------
-- CASE SPLITTING
----------------------------------------------------------------
data SplitInfo = SplitInfo G.Name SrcSpan (SrcSpan, Type) [SrcSpan]
| TySplitInfo G.Name SrcSpan (SrcSpan, Ty.Kind)
data SplitToTextInfo = SplitToTextInfo { sVarName :: String
, sBindingSpan :: SrcSpan
, sVarSpan :: SrcSpan
, sTycons :: [String]
}
-- | Splitting a variable in a equation.
splits :: IOish m
=> FilePath -- ^ A target file.
-> Int -- ^ Line number.
-> Int -- ^ Column number.
-> GhcModT m String
splits file lineNo colNo = ghandle handler body
where
body = inModuleContext file $ \dflag style -> do
opt <- options
modSum <- Gap.fileModSummary file
whenFound' opt (getSrcSpanTypeForSplit modSum lineNo colNo) $ \x -> case x of
(SplitInfo varName bndLoc (varLoc,varT) _matches) -> do
let varName' = showName dflag style varName -- Convert name to string
text <- genCaseSplitTextFile file (SplitToTextInfo varName' bndLoc varLoc $
getTyCons dflag style varName varT)
return (fourInts bndLoc, text)
(TySplitInfo varName bndLoc (varLoc,varT)) -> do
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let varName' = showName dflag style varName -- Convert name to string
text <- genCaseSplitTextFile file (SplitToTextInfo varName' bndLoc varLoc $
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getTyCons dflag style varName varT)
return (fourInts bndLoc, text)
handler (SomeException _) = emptyResult =<< options
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----------------------------------------------------------------
-- a. Code for getting the information of the variable
getSrcSpanTypeForSplit :: GhcMonad m => G.ModSummary -> Int -> Int -> m (Maybe SplitInfo)
getSrcSpanTypeForSplit modSum lineNo colNo = do
fn <- getSrcSpanTypeForFnSplit modSum lineNo colNo
if isJust fn
then return fn
else getSrcSpanTypeForTypeSplit modSum lineNo colNo
-- Information for a function case split
getSrcSpanTypeForFnSplit :: GhcMonad m => G.ModSummary -> Int -> Int -> m (Maybe SplitInfo)
getSrcSpanTypeForFnSplit modSum lineNo colNo = do
p@ParsedModule{pm_parsed_source = pms} <- G.parseModule modSum
tcm@TypecheckedModule{tm_typechecked_source = tcs} <- G.typecheckModule p
let varPat = find isPatternVar $ listifySpans tcs (lineNo, colNo) :: Maybe (LPat Id)
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match:_ = listifyParsedSpans pms (lineNo, colNo) :: [Gap.GLMatch]
case varPat of
Nothing -> return Nothing
Just varPat' -> do
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varT <- Gap.getType tcm varPat' -- Finally we get the type of the var
case varT of
Just varT' ->
let (L matchL (G.Match _ _ (G.GRHSs rhsLs _))) = match
in return $ Just (SplitInfo (getPatternVarName varPat') matchL varT' (map G.getLoc rhsLs) )
_ -> return Nothing
isPatternVar :: LPat Id -> Bool
isPatternVar (L _ (G.VarPat _)) = True
isPatternVar _ = False
getPatternVarName :: LPat Id -> G.Name
getPatternVarName (L _ (G.VarPat vName)) = G.getName vName
getPatternVarName _ = error "This should never happened"
-- TODO: Information for a type family case split
getSrcSpanTypeForTypeSplit :: GhcMonad m => G.ModSummary -> Int -> Int -> m (Maybe SplitInfo)
getSrcSpanTypeForTypeSplit _modSum _lineNo _colNo = return Nothing
----------------------------------------------------------------
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-- b. Code for getting the possible constructors
getTyCons :: DynFlags -> PprStyle -> G.Name -> G.Type -> [String]
getTyCons dflag style name ty | Just (tyCon, _) <- Ty.splitTyConApp_maybe ty =
let name' = showName dflag style name -- Convert name to string
in getTyCon dflag style name' tyCon
getTyCons dflag style name _ = [showName dflag style name]
-- Write cases for one type
getTyCon :: DynFlags -> PprStyle -> String -> Ty.TyCon -> [String]
-- 1. Non-matcheable type constructors
getTyCon _ _ name tyCon | isNotMatcheableTyCon tyCon = [name]
-- 2. Special cases
-- 2.1. Tuples
getTyCon _ _ name tyCon | Ty.isTupleTyCon tyCon =
let [uniqueDataCon] = Ty.tyConDataCons tyCon
tupleArity = Ty.dataConSourceArity uniqueDataCon
-- Deal with both boxed and unboxed tuples
isUnboxed = Ty.isUnboxedTupleTyCon tyCon
startSign = if isUnboxed then "(#" else "("
endSign = if isUnboxed then "#)" else ")"
in [ startSign ++ intercalate "," (map (\n -> name ++ show n) [1 .. tupleArity]) ++ endSign ]
-- 3. General case
getTyCon dflag style name tyCon = map (getDataCon dflag style name) (Ty.tyConDataCons tyCon)
-- These type constructors should not be matched against
isNotMatcheableTyCon :: Ty.TyCon -> Bool
isNotMatcheableTyCon ty = Ty.isPrimTyCon ty -- Primitive types, such as Int#
|| Ty.isFunTyCon ty -- Function types
-- Write case for one constructor
getDataCon :: DynFlags -> PprStyle -> String -> Ty.DataCon -> String
-- 1. Infix constructors
getDataCon dflag style vName dcon | Ty.dataConIsInfix dcon =
let dName = showName dflag style $ Ty.dataConName dcon
in case Ty.dataConSourceArity dcon of
0 -> dName
1 -> vName ++ dName
n -> if dName == ":" -- Special case for lists
then vName ++ ":" ++ vName ++ "s"
else newVar vName 1 ++ " " ++ dName ++ " " ++ newVars vName 2 (n-1)
-- 2. Non-record, non-infix syntax
getDataCon dflag style vName dcon | [] <- Ty.dataConFieldLabels dcon =
let dName = showName dflag style $ Ty.dataConName dcon
in if last dName == '#' -- Special case for I#, C# and so on
then vName
else case Ty.dataConSourceArity dcon of
0 -> dName
_ -> dName ++ " " ++ newVarsSpecialSingleton vName 1 (Ty.dataConSourceArity dcon)
-- 3. Records
getDataCon dflag style vName dcon =
let dName = showName dflag style $ Ty.dataConName dcon
flds = Ty.dataConFieldLabels dcon
in dName ++ " { " ++ showFieldNames dflag style vName flds ++ " }"
-- Create a new variable by adjoining a number
newVar :: String -> Int -> String
newVar v n = v ++ show n
-- Create a list of variables which start with the same prefix
newVars :: String -> Int -> Int -> String
newVars _ _ 0 = ""
newVars v s 1 = newVar v s
newVars v s m = newVar v s ++ " " ++ newVars v (s+1) (m-1)
-- Create a list of variables which start with the same prefix
-- Special case for a single variable, in which case no number is adjoint
newVarsSpecialSingleton :: String -> Int -> Int -> String
newVarsSpecialSingleton v _ 1 = v
newVarsSpecialSingleton v start n = newVars v start n
showFieldNames :: DynFlags -> PprStyle -> String -> [G.Name] -> String
showFieldNames _ _ _ [] = "" -- This should never happen
showFieldNames dflag style v (x:xs) = let fName = showName dflag style x
fAcc = fName ++ " = " ++ v ++ "_" ++ fName
in case xs of
[] -> fAcc
_ -> fAcc ++ ", " ++ showFieldNames dflag style v xs
----------------------------------------------------------------
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-- c. Code for performing the case splitting
genCaseSplitTextFile :: GhcMonad m => FilePath -> SplitToTextInfo -> m String
genCaseSplitTextFile file info = liftIO $ do
text <- T.readFile file
return $ getCaseSplitText (T.lines text) info
getCaseSplitText :: [T.Text] -> SplitToTextInfo -> String
getCaseSplitText text (SplitToTextInfo { sVarName = sVN, sBindingSpan = sBS
, sVarSpan = sVS, sTycons = sT }) =
let bindingText = getBindingText text sBS
difference = srcSpanDifference sBS sVS
replaced = concatMap (replaceVarWithTyCon bindingText difference sVN) sT
in T.unpack $ T.intercalate (T.pack "\n") replaced
getBindingText :: [T.Text] -> SrcSpan -> [T.Text]
getBindingText text srcSpan =
let Just (sl,sc,el,ec) = Gap.getSrcSpan srcSpan
lines_ = drop (sl - 1) $ take el text
in if sl == el
then -- only one line
[T.drop (sc - 1) $ T.take ec $ head lines_]
else -- several lines
let (first,rest,last_) = (head lines_, tail $ init lines_, last lines_)
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in T.drop (sc - 1) first : rest ++ [T.take ec last_]
srcSpanDifference :: SrcSpan -> SrcSpan -> (Int,Int,Int,Int)
srcSpanDifference b v =
let Just (bsl,bsc,_ ,_) = Gap.getSrcSpan b
Just (vsl,vsc,vel,vec) = Gap.getSrcSpan v
in (vsl - bsl, vsc - bsc, vel - bsl, vec - bsc) -- assume variable in one line
replaceVarWithTyCon :: [T.Text] -> (Int,Int,Int,Int) -> String -> String -> [T.Text]
replaceVarWithTyCon text (vsl,vsc,_,vec) varname tycon =
let tycon' = if ' ' `elem` tycon || ':' `elem` tycon then "(" ++ tycon ++ ")" else tycon
lengthDiff = length tycon' - length varname
tycon'' = T.pack $ if lengthDiff < 0 then tycon' ++ replicate (-lengthDiff) ' ' else tycon'
spacesToAdd = if lengthDiff < 0 then 0 else lengthDiff
in zipWith (\n line -> if n < vsl
then line -- before variable starts
else if n == vsl
then T.take vsc line `T.append` tycon'' `T.append` T.drop vec line
else T.replicate spacesToAdd (T.pack " ") `T.append` line)
[0 ..] text