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|
module Compiler where
import qualified Ast as A
import Control.Monad.State
import Data.Either (rights)
import Env
import Error
import System.Environment (getEnv, getEnvironment)
import Text.Parsec (ParseError, SourcePos)
import Text.Read (Lexeme (String))
type CompState = (Env, [Error])
type CompResult = Either [Error] (Maybe A.Type)
startState :: CompState
startState = (emptyEnv, [])
-- | @foldlEither fn init xs@ folds left @xs@ applying a function @fn@ that
-- returns either, returning accumulated right and the collected lefts as a
-- list.
foldlEither :: (accr -> b -> Either accl accr) -> (accr, [accl]) -> [b] -> (accr, [accl])
foldlEither fn init xs =
foldl
( \(r, l) x -> case fn r x of
Left e -> (r, e : l)
Right x -> (x, l)
)
init
xs
-- | @addError error@ adds @error@ to the state and returns no type to allow
-- the compilation to continue.
addError :: Error -> State CompState CompResult
addError e = do
(ev, errs) <- get
put (ev, e : errs)
return $ Right Nothing
-- | @typecheckCall args params@ resolves @args@ and compares it with @params@,
-- returning a string describing an error or Nothing in case of type match.
typecheckCall :: [A.Expr] -> [A.Type] -> State CompState (Maybe String)
typecheckCall args params
| length args /= length params = return $ Just "invalid number of arguments in function call"
| length params == 0 = return $ Nothing
| otherwise = do
-- resolve all args types
targs <- fmap rights $ traverse compile args
case sequence targs of
Just t ->
if length t /= length params
then -- there was an error in one argument
return $ Nothing
else
if all (\(a, b) -> a == b) $ zip t params -- compare types
then return $ Nothing -- all good!
else return $ Just ("type mismatch in function call:\n unexpected " ++ A.showList t ++ "\n expecting " ++ A.showList params)
Nothing ->
-- there was an error in on argument
return $ Nothing
-- | @typecheckReturn value fret@ resolves @value@ and compares it with @fret@,
-- returning a string decribing an error or Nothing in case of a type match.
typecheckReturn :: Maybe A.Expr -> Maybe A.Type -> State CompState (Maybe String)
typecheckReturn Nothing Nothing = return $ Nothing
typecheckReturn (Just value) fret = do
r <- compile value
case r of
Right r ->
if r == fret
then return $ Nothing
else return $ Just $ "invalid return value:\n unexpected " ++ showMaybet r ++ "\n expecting " ++ showMaybet fret
Left _ -> return $ Nothing -- error resolving return value
where
showMaybet :: Maybe A.Type -> String
showMaybet Nothing = "()"
showMaybet (Just t) = show t
compile :: A.Expr -> State CompState CompResult
compile x = do
case x of
(A.Module name pos) -> return $ Right Nothing
(A.Num _ _) -> return $ Right $ Just $ A.Type "u8" -- TODO: placeholder
(A.BinOp _ a b) -> do
l <- compile a
r <- compile b
return $ l -- TODO: placeholder
(A.Func ident params ret body priv pos) -> do
-- current env
(ev, errs) <- get
-- updated with the function
(ev, errs) <-
return $ case addSymUniq ev (ident, ftype, pos) of
Left err -> (ev, err : errs)
Right ev -> (ev, errs)
-- with parameters
(nev, errs) <- return $ foldlEither addSymUniq (addEnv ev, errs) params
-- helper for return
nev <- return $ addSym nev ("$fn$", ftype, pos)
put (nev, errs)
r <- compileAll body
(_, errs) <- get
-- store updated errors and the env with the function
put (ev, errs)
return $ Right $ Just ftype
where
ftype = A.toFuncType params ret
(A.Call ident args pos) -> do
r <- compile ident
case r of
p@(Right (Just (A.FuncType params rtyp))) -> do
r <- typecheckCall args params
case r of
Just err -> addError $ Error err pos
Nothing -> return $ Right rtyp
(A.Return value pos) -> do
(ev, errs) <- get
case getSyml ev "$fn$" of
Nothing -> addError $ Error "return without function call" pos
Just (_, A.FuncType _ rtyp, _) -> do
r <- typecheckReturn value rtyp
case r of
Just err -> addError $ Error err pos
Nothing -> return $ Right rtyp
(A.Var ident pos) -> do
(ev, errs) <- get
case getSym ev ident of
Just (_, t, _) -> return $ Right $ Just t
Nothing -> addError $ Error ("undefined variable \"" ++ ident ++ "\"") pos
compileAll :: [A.Expr] -> State CompState CompResult
compileAll (x : xs) = do
compile x
compileAll xs
compileAll [] = do
(_, errs) <- get
case errs of
[] -> return $ Right Nothing
_ -> return $ Left errs
|
