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tcLookupDataFamInst_maybe :: FamInstEnvs -> TyCon -> [TcType] -> Maybe (TyCon, [TcType], Coercion)ghc-lib GHC.Tc.Instance.Family Converts a data family type (eg F [a]) to its representation type (eg FList a) and returns a coercion between the two: co :: F [a] ~R FList a.
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ghc-lib GHC.Tc.Instance.Family tcTopNormaliseNewTypeTF_maybe gets rid of top-level newtypes, potentially looking through newtype instances and type synonyms. It is only used by the type inference engine (specifically, when solving representational equality), and hence it is careful to unwrap only if the relevant data constructor is in scope. That's why it gets a GlobalRdrEnv argument. It is careful not to unwrap data/newtype instances nor synonyms if it can't continue unwrapping. Such care is necessary for proper error messages. It does not look through type families. It does not normalise arguments to a tycon. If the result is Just ((gres, co), rep_ty), then co : ty ~R rep_ty gres are the GREs for the data constructors that had to be in scope
isFilledMetaTyVar_maybe :: TcTyVar -> TcS (Maybe Type)ghc-lib GHC.Tc.Solver.Monad No documentation available.
lookupGlobal_maybe :: HscEnv -> Name -> IO (MaybeErr (Either Name IfaceMessage) TyThing)ghc-lib GHC.Tc.Utils.Env No documentation available.
tcLookupIdMaybe :: Name -> TcM (Maybe Id)ghc-lib GHC.Tc.Utils.Env No documentation available.
tcLookupLcl_maybe :: Name -> TcM (Maybe TcTyThing)ghc-lib GHC.Tc.Utils.Env No documentation available.
checkingExpType_maybe :: ExpType -> Maybe TcTypeghc-lib GHC.Tc.Utils.TcMType Returns the expected type when in checking mode.
isFilledMetaTyVar_maybe :: TcTyVar -> TcM (Maybe Type)ghc-lib GHC.Tc.Utils.TcMType No documentation available.
readExpType_maybe :: MonadIO m => ExpType -> m (Maybe TcType)ghc-lib GHC.Tc.Utils.TcMType Extract a type out of an ExpType, if one exists. But one should always exist. Unless you're quite sure you know what you're doing.
unpackCoercionHole_maybe :: CoercionHole -> TcM (Maybe Coercion)ghc-lib GHC.Tc.Utils.TcMType Retrieve the contents of a coercion hole, if it is filled