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module Internal.Constraint (module TcPluginM, flatToCt, overEvidencePredType) where
import GhcApi.GhcPlugins
import GhcApi.Constraint
(Ct(..), CtEvidence(..), ctLoc, ctEvId, mkNonCanonical)
import TcType (TcType)
import TcPluginM (newGiven)
flatToCt :: [((TcTyVar,TcType),Ct)] -> Maybe Ct
flatToCt [((_,lhs),ct),((_,rhs),_)]
= Just
$ mkNonCanonical
$ CtGiven (mkPrimEqPred lhs rhs)
(ctEvId (cc_ev ct))
(ctLoc ct)
flatToCt _ = Nothing
-- | Modify the predicate type of the evidence term of a constraint
overEvidencePredType :: (TcType -> TcType) -> Ct -> Ct
overEvidencePredType f ct =
let
ev :: CtEvidence
ev = cc_ev ct
in ct { cc_ev = ev { ctev_pred = f (ctev_pred ev) } }
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