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Drop undecidable Ord instance for ParseError.

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That code fails to compile with ghc-8.6.1 because the instance is undecidable.
I suppose we could enable the appropriate compiler extension to support it, but
I've found that simply removing the instance causes no problems whatsoever: the
entire repository still compiles fine and it passes all test suites, too.
This commit is contained in:
Peter Simons 2018-10-24 12:26:14 +02:00 committed by Simon Michael
parent 4e8f2c11d3
commit 027d084878
1 changed files with 0 additions and 3 deletions
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3
hledger-lib/Text/Megaparsec/Custom.hs
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@ -2,7 +2,6 @@
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE PackageImports #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE StandaloneDeriving #-}
module Text.Megaparsec.Custom (
-- * Custom parse error type
@ -67,8 +66,6 @@ data CustomErr
-- derive it, but this requires an (orphan) instance for 'ParseError'.
-- Hopefully this does not cause any trouble.
deriving instance (Eq (Token c), Ord (Token c), Ord c, Ord e) => Ord (ParseError c e)
instance ShowErrorComponent CustomErr where
showErrorComponent (ErrorFailAt _ _ errMsg) = errMsg
errorComponentLen (ErrorFailAt startOffset endOffset _) =