]> Git — Sourcephile - haskell/symantic.git/blob - symantic-grammar/Language/Symantic/Grammar/Error.hs
Rename grammar rules.
[haskell/symantic.git] / symantic-grammar / Language / Symantic / Grammar / Error.hs
1 {-# LANGUAGE TypeApplications #-}
2 module Language.Symantic.Grammar.Error where
3
4 import Data.Proxy (Proxy)
5
6 -- * Class 'ErrorInj'
7 class ErrorInj a b where
8 errorInj :: a -> b
9 instance ErrorInj err e => ErrorInj err (Either e a) where
10 errorInj = Left . errorInj
11
12 liftError ::
13 forall e0 err e1 a.
14 ErrorInj e0 e1 =>
15 ErrorInj e1 err =>
16 Proxy e1 -> Either e0 a -> Either err a
17 liftError _e1 (Right a) = Right a
18 liftError _e1 (Left e) = Left $ errorInj @e1 @err $ errorInj @e0 @e1 e