28 lines
808 B
Haskell
28 lines
808 B
Haskell
-- | Error handling and reporting.
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module Errors where
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import qualified AST as A
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import Metadata
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-- | Class of monads that can fail.
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class Monad m => Die m where
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-- | Fail, giving an error message.
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die :: String -> m a
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-- | Fail, giving a position and an error message.
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dieP :: Die m => Meta -> String -> m a
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dieP m s = die $ show m ++ ": " ++ s
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-- | Wrapper around error that gives nicer formatting.
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dieIO :: Monad m => String -> m a
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dieIO s = error $ "\n\nError: " ++ s ++ "\n"
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-- | Fail after an internal error.
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dieInternal :: Monad m => String -> m a
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dieInternal s = dieIO $ "Internal error: " ++ s
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-- | Extract a value from a Maybe type, dying with the given error if it's Nothing.
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checkJust :: Die m => String -> Maybe t -> m t
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checkJust _ (Just v) = return v
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checkJust err _ = die err
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