ghc-7.10.1: The GHC API

Safe HaskellNone




tcLookupDataFamInst :: FamInstEnvs -> TyCon -> [TcType] -> (TyCon, [TcType], TcCoercion) Source

Like tcLookupDataFamInst_maybe, but returns the arguments back if there is no data family to unwrap.

tcLookupDataFamInst_maybe :: FamInstEnvs -> TyCon -> [TcType] -> Maybe (TyCon, [TcType], Coercion) Source

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

tcInstNewTyCon_maybe :: TyCon -> [TcType] -> Maybe (TcType, TcCoercion) Source

If co :: T ts ~ rep_ty then:

instNewTyCon_maybe T ts = Just (rep_ty, co)

Checks for a newtype, and for being saturated Just like Coercion.instNewTyCon_maybe, but returns a TcCoercion

tcTopNormaliseNewTypeTF_maybe :: FamInstEnvs -> GlobalRdrEnv -> Type -> Maybe (TcCoercion, Type) Source

Get rid of top-level newtypes, potentially looking through newtype instances. Only unwraps newtypes that are in scope. This is used for solving for Coercible in the solver. This version is careful not to unwrap data/newtype instances if it can't continue unwrapping. Such care is necessary for proper error messages.

Does not look through type families. Does not normalise arguments to a tycon.

Always produces a representational coercion.