text: var isVNode = require("vtree/is-vnode")
  var isVText = require("vtree/is-vtext")
  var isWidget = require("vtree/is-widget")
  var isThunk = require("vtree/is-thunk")
  
  module.exports = handleThunk
  
  function handleThunk(a, b) {
      return { a: isThunk(a) ? renderThunk(a, null) : null
             , b: isThunk(b) ? renderThunk(b, a) : null
             }
  }
  
  function renderThunk(thunk, previous) {
      if(thunk.vnode) return null;
      thunk.render(previous);
      return thunk.vnode ? null : thunk;
  }
  