源码中的两个函数

   function generate(
        ast,
        options
    ) {
        var state = new CodegenState(options);
        var code = ast ? genElement(ast, state) : '_c("div")';
        return {
            render: ("with(this){return " + code + "}"),
            staticRenderFns: state.staticRenderFns
        }
    }

function genStatic(el, state) {
    el.staticProcessed = true;
    state.staticRenderFns.push(("with(this){return " + (genElement(el, state)) + "}"));
    return ("_m(" + (state.staticRenderFns.length - 1) + (el.staticInFor ? ',true' : '') + ")")
}

在vm.$options.render中

function() {
    with(this){return _c("div")}
}

Vue.prototype._c， 仅仅是为了省略this吗，with不是存在性能问题么，而且严格模式也不支持。