function isWithoutDefaultValue(prop) {
      if (prop.value.type !== 'ObjectExpression') {
        if (prop.value.type === 'Identifier') {
          return NATIVE_TYPES.has(prop.value.name)
        }
        if (
          prop.value.type === 'CallExpression' ||
          prop.value.type === 'MemberExpression'
        ) {
          // OK
          return false
        }
        // NG
        return true
      }

      return !propIsRequired(prop.value) && !propHasDefault(prop.value)
    }
Checks whether the given props that don't have a default value
@param {ComponentObjectProp} prop Vue component's "props" node
@return {boolean}