Java 9 ea154 javac compiler error - legit or bug?

[Maurizio Cimadamore]

Hi,
it seems like the behavior you observed started in b83 - as a result of 
this:

https://bugs.openjdk.java.net/browse/JDK-8078093

I believe the error is correct (although the diagnostic has always been 
broken since b83 in the 'verbose' mode - the non-verbose mode - w/o 
-Xdiags:verbose is fine). That is, the call to 'foo' is unchecked, so 
the return type should be erased. There seems to be an inconsistency in 
how javac handles this in method context compared to assignment context, 
and that needs to be looked at.

Thanks
Maurizio



On 08/02/17 19:23, Vitaly Davidovich wrote:
> Hi all,
>
> Given the following code:
>
> import java.util.ArrayList;
> import java.util.Collection;
>
> public class Foo {
>     static <T> T foo(Class<T> c, Collection<? super T> baz) {
> return null;
>     }
>
>     static void bar(String c) {
>
>     }
>
>     @SuppressWarnings("unchecked")
>     public static void main(String[] args) {
> // this works
> bar(foo(String.class, new ArrayList<String>()));
>
> // this works with a warning
> String s = foo(String.class, new ArrayList());
> bar(s);
>
> // this causes an error on JDK9
> bar(foo(String.class, new ArrayList()));
>     }
> }
>
> javac 9-ea (build 9-ea+154) fails with this interesting error (on the 
> last line in main, as the comments there indicate):
>
> Foo.java:23: error: method bar in class Foo cannot be applied to given 
> types;
>                 bar(foo(String.class, new ArrayList()));
>                 ^
>   required: String
>   found: String
>   reason: argument mismatch; Object cannot be converted to String
> 1 error
>
> Java 8 compiles fine, and the other 2 lines compile in the same java 9 
> build as well.
>
> Is this a javac bug or legit? It seems like a compiler error.  At a 
> minimum, the diagnostic output "required String, found String" is 
> confusing.
>
> Thanks
>
>

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