* @param env      the current environment
     */
    void attribTypeVariables(List<JCTypeParameter> typarams, Env<AttrContext> env) {
        for (JCTypeParameter tvar : typarams) {
            TypeVar a = (TypeVar)tvar.type;
            a.tsym.flags_field |= UNATTRIBUTED;
            a.bound = Type.noType;
            if (!tvar.bounds.isEmpty()) {
                List<Type> bounds = List.of(attribType(tvar.bounds.head, env));
                for (JCExpression bound : tvar.bounds.tail)
                    bounds = bounds.prepend(attribType(bound, env));
                types.setBounds(a, bounds.reverse());
            } else {
                // if no bounds are given, assume a single bound of
                // java.lang.Object.
                types.setBounds(a, List.of(syms.objectType));
            }
            a.tsym.flags_field &= ~UNATTRIBUTED;
        }
        for (JCTypeParameter tvar : typarams)
            chk.checkNonCyclic(tvar.pos(), (TypeVar)tvar.type);
        attribStats(typarams, env);
    }