然而，对于所有的方法参数来说，类型注解是必须的。

However, type annotations are required for all method parameters.

youdao

这里有一份关于scala何时需要显式类型注解规则的总结。

Here is a summary of the rules for when explicit type annotations are required in Scala.

youdao

所以，scala比haskell这样的语言需要更多的类型注解。

So, Scala requires more type annotations than languages like Haskell.

youdao