public void visitTypeParameter(JCTypeParameter tree) {
        TypeVar a = (tree.type != null)
            ? (TypeVar)tree.type
            : new TypeVar(tree.name, env.info.scope.owner, syms.botType);
        tree.type = a;
        if (chk.checkUnique(tree.pos(), a.tsym, env.info.scope)) {
            env.info.scope.enter(a.tsym);
        }
        result = a;
    }