情况下，当清单不可用 [英] Situations when Manifest not available

问题描述

def bar[T: Manifest](a: Array[T]) = Array.ofDim[T](3)

class Foo

bar(Array(new Foo))  //Array[Foo] = Array(null, null, null)

舱单似乎暗示存在任意类型，如上所示。

Manifests seem to exist implicitly for arbitrary types, as shown above.

由于我们有约束的情况下，这意味着会有一些类型其中有没有隐含的清单 - 它们是什么

Since we have a context bound, this implies that there will be some types for which there is no implicit Manifest - what are they?

推荐答案

一个清单具有由点到是携带，其中具体类型最后出现在源$ C ​​$ C，通过类型参数的一路放置在它是必需的。

A Manifest has to be "carried" from the point where the concrete type last appears in the source code, all the way through type parameters to the place where it is required.

但凡事都有一个清单。

这篇关于情况下，当清单不可用的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！