tcExtendLocalFamInstEnv :: [FamInst] -> TcM a -> TcM a

-- If we weren't actually given any instances to add, then we don't want
-- to go to the bother of loading family instance module dependencies.
tcExtendLocalFamInstEnv [] thing_inside = thing_inside
tcExtendLocalFamInstEnv :: [FamInst] -> TcM a -> TcM a
tcExtendLocalFamInstEnv [] thing_inside = thing_inside
tcExtendLocalFamInstEnv [] thing_inside = thing_inside