function genDefaultModel (
 el: ASTElement,
 value: string,
 modifiers: ?ASTModifiers
): ?boolean {
 const type = el.attrsMap.type
 const { lazy, number, trim } = modifiers || {}
 const needCompositionGuard = !lazy && type !== 'range'
 const event = lazy
  ? 'change'
  : type === 'range'
   ? RANGE_TOKEN
   : 'input'

 let valueExpression = '$event.target.value'
  // 去掉空格
 if (trim) {
  valueExpression = `$event.target.value.trim()`
 }
 if (number) {
  valueExpression = `_n(${valueExpression})`
 }

 let code = genAssignmentCode(value, valueExpression)
 if (needCompositionGuard) {
  code = `if($event.target.composing)return;$[code]`
 }

 addProp(el, 'value', `(${value})`)
 addHandler(el, event, code, null, true)
 if (trim || number || type === 'number') {
  addHandler(el, 'blur', '$forceUpdate()')
 }
}