message: refactor: use more accurate variable name
diff: @@ -292,7 +292,7 @@ function initWatch (vm: Component, watch: Object) {
  function createWatcher (
  vm: Component,
  - keyOrFn: string | Function,
  + expOrFn: string | Function,
  handler: any,
  options?: Object
  ) {
  @@ -303,7 +303,7 @@ function createWatcher (
  if (typeof handler === 'string') {
  handler = vm[handler]
  }
  - return vm.$watch(keyOrFn, handler, options)
  + return vm.$watch(expOrFn, handler, options)
  }
  export function stateMixin (Vue: Class<Component>) {
  