投射到带有泛型的内部类 [英] Casting to an inner class with generics

问题描述

请考虑以下代码：

public class Outer<T>  {

    public class Inner{
    }

    public static <T> Outer<T>.Inner get(){
        Object o = new Object();
        return (Outer<T>.Inner)o;
    }

    public static void main(String[] args) throws Exception {
        Outer.<String>get();
    }
}

此代码在Eclipse中成功编译，但无法编译在 javac ：

This code compiles successfully in Eclipse, but fails to compile in javac:

Outer.java:10: ')' expected
        return (Outer<T>.Inner)o;
                        ^
Outer.java:10: ';' expected
        return (Outer<T>.Inner)o;
                         ^
Outer.java:10: illegal start of expression
        return (Outer<T>.Inner)o;
                              ^
3 errors

这是 javac 或Eclipse？

Is this a bug in javac or Eclipse?

如果我将转换改为（Outer.Inner）o 它编译，虽然有一个警告：

If I change the cast to (Outer.Inner)o it compiles, although there is a warning:

Eclipse：

Outer.Inner is a raw type. References to generic type Outer<T>.Inner should be parameterized

javac：

Outer.java:10: warning: [unchecked] unchecked conversion
found   : Outer.Inner
required: Outer<T>.Inner
        return (Outer.Inner)o;
               ^
1 warning

Javac版本 1.6.0_21

Javac version: 1.6.0_21

推荐答案

我发现这是javac编译器中一个已经修复的错误。

I have found that this is a bug in the javac compiler that has since been fixed. JDK 7b100 compiles this fine.

请参阅 http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6665356

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