diff options
| author | Camil Staps | 2018-02-08 10:08:12 +0100 |
|---|---|---|
| committer | Camil Staps | 2018-02-08 10:08:12 +0100 |
| commit | a15f77f060a34e2987886467752892b58ff445dc (patch) | |
| tree | 8d20d25ab5ce02d7740a275259904abb9bf7bd91 /src | |
| parent | Report Skeleton (diff) | |
More meaningful error messages
Diffstat (limited to 'src')
| -rw-r--r-- | src/SPL/Parse.hs | 27 |
1 files changed, 15 insertions, 12 deletions
diff --git a/src/SPL/Parse.hs b/src/SPL/Parse.hs index 28230f8..eec7fd1 100644 --- a/src/SPL/Parse.hs +++ b/src/SPL/Parse.hs @@ -19,11 +19,14 @@ type Parser t = P.Parsec [Token] () t parse :: [Token] -> Either P.ParseError Program parse = P.parse spl "Not a valid program" . filter (not . isCommentToken) -check :: (Token -> Maybe a) -> Parser a -check f = P.tokenPrim show (const . const) f +check :: String -> (Token -> Maybe a) -> Parser a +check e f = P.tokenPrim show (\p _ _ -> P.incSourceColumn p 1) f <?> e +-- TODO: We increment the source column to get meaningful error messages; +-- the error that is furthest in the parsing process. We need to keep positions +-- in the list of tokens so that we can update this properly. token :: Token -> Parser Token -token t = check (\u -> if t == u then Just t else Nothing) +token t = check (show t) (\u -> if t == u then Just t else Nothing) choice :: [Parser a] -> Parser a choice = P.choice . map P.try @@ -44,7 +47,7 @@ toplevel = choice ] comment :: Parser String -comment = check $ \case +comment = check "comment" $ \case TSingleComment s -> Just s TBlockComment s -> Just s _ -> Nothing @@ -70,16 +73,16 @@ var = do fun :: Parser Function fun = do id <- ident - args <- parenthesised (ident `sepBy` token TComma) <?> "arguments" - ftype <- optional (token TColonColon *> funType) <?> "optional function type" + args <- parenthesised (ident `sepBy` token TComma) + ftype <- optional (token TColonColon *> funType) token TBraceOpen - vars <- many (P.try var) <?> "local variables" - stmt <- statements <?> "function body" + vars <- many (P.try var) + stmt <- statements token TBraceClose return $ Function id ftype args vars stmt ident :: Parser Name -ident = check $ \case +ident = check "identifier" $ \case TIdent id -> Just id _ -> Nothing @@ -147,7 +150,7 @@ expr = ] literal :: Parser Expression - literal = fmap Literal $ nil <|> (check $ \case + literal = fmap Literal $ nil <|> (check "literal" $ \case TInt i -> Just (LInt i) TBool b -> Just (LBool b) TChar c -> Just (LChar c) @@ -161,7 +164,7 @@ expr = var = Var <$> ident statements :: Parser Statement -statements = foldr1 Seq <$> some statement <|> pure Nop +statements = (foldr1 Seq <$> some statement <|> pure Nop) <?> "statement" -- NOTE: we here assume that if/while blocks need not be braced, as in the -- example function `abs`. The alternative is using `braced statements`. @@ -184,7 +187,7 @@ statement = choice ] field :: Parser Field -field = token TDot *> check (\case +field = token TDot *> check "field" (\case TIdent "hd" -> Just Hd TIdent "tl" -> Just Tl TIdent "fst" -> Just Fst |