Scala 2.10.0 RC2 和可选参数 [英] Scala 2.10.0 RC2 and optional parameters

问题描述

我正在试验 Scala 宏，它们是 Scala 2.10 的一部分，但是当我尝试编译时(使用 sbt) 我收到以下错误:

I am experimentin with Scala Macros, which are part of Scala 2.10, but as I try to compile (Using sbt) I get the following error:

[error] .../API.scala:9: not enough arguments for constructor OAuth:
(requestMethod: String, consumerSecret: String, consumerKey: String,
signatureMethod: String, version: String)jm.oauth.OAuth
[error]   private val oauth = new OAuth(OAuth.POST, oauthConsumerSecret,
oauthConsumerKey, OAuth.HMAC_SHA1)

你可以找到OAuth类的实现此处.

scala 2.10 和可选参数是否有任何不兼容?

Is there any incompatibility between scala 2.10 and optional parameters?

使用 Scala 2.9.1 编译的完全相同的代码运行良好.

The very same code, compiled with scala 2.9.1, worked perfectly.

推荐答案

如果您创建的文件只包含此类定义:

If you create a file containing only this class definition:

class Optional(x: Int = 0)

然后用 Scala 2.9.2 编译它并在生成的类上运行 javap，你会看到:

Then compile it with Scala 2.9.2 and run javap on the resulting class, you'll see this:

public class Optional implements scala.ScalaObject {
  public static final int init$default$1();
  public Optional(int);
}

用 2.10.0-RC2 和 javap 再次编译它，你会得到这个:

Compile it again with 2.10.0-RC2 and javap it, and you get this instead:

public class Optional {
  public static int $lessinit$greater$default$1();
  public Optional(int);
}

所以不，默认参数在 2.10 中完全没问题，您刚刚遇到了一个具体示例，说明主要 Scala 版本之间缺乏二进制兼容性.

So no, default arguments are perfectly fine in 2.10, you've just run into a concrete example of the lack of binary compatibility between major Scala versions.

这篇关于Scala 2.10.0 RC2 和可选参数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！