+varTypeTcTyVars :: Var -> TyVarSet
+-- Find the type variables free in the type of the variable
+-- Remember, coercion variables can mention type variables...
+varTypeTcTyVars var
+ | isLocalId var || isCoVar var = tcTyVarsOfType (idType var)
+ | otherwise = emptyVarSet -- Global Ids and non-coercion TyVars
+