error vs. warning for casting Class<? extends Collection<?>>

[nradov at axolotl.com]

This code fails to compile using javac 1.6 or 1.7 beta.

import java.util.Collection;
import java.util.Set;

class Test {
    Class<? extends Collection<?>> x = (Class<? extends Collection<?>>) 
Set.class;
}

Here is the error.

C:\>javac Test.java
Test.java:5: inconvertible types
    Class<? extends Collection<?>> x = (Class<? extends Collection<?>>) 
Set.class;
 ^
  required: Class<? extends Collection<?>>
  found:    Class<Set>

However the same code produces only a warning in the Eclipse Galileo 
compiler.

Type safety: Unchecked cast from Class<Set> to Class<? extends 
Collection<?>>

So there's a bug in one of the compilers but I can't figure out which is 
wrong. Is this the same as Bug ID: 6557279 <
http://bugs.sun.com/view_bug.do?bug_id=6557279> or is it something 
different?

Nick Radov | Director, Research & Development | Axolotl Corp

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