On Sat, Mar 28, 2009 at 11:55 PM, Scott Blum <[email protected]> wrote:
> Two things:
> 1) Do you have to use a temp, or can you do something
> like artifacts. <EmittedArtifact> find(EmittedArtifact.class)? Or whatever
> the syntax is.
>
It could also be:
for (EmittedArtifact artifact : artifacts.<EmittedArtifact,
EmittedArtifact>find(EmittedArtifact.class)) {
etc if you prefer -- do you think that is cleaner? The problem here is that
OpenJDK can't seem to properly infer A=EmittedArtifact from the return type
SortedSet<A extends Artifact<?>> where EmittedArtifact extends
Artifact<EmittedArtifact> (defined as Artifact<C extends Artifact<C>>).
This is just one case of a general class of recursive definitions which
OpenJDK fails to infer, and the Sun guy working on it has determined that
the old javac accepted in violation of JLS. Since this seems very similar
to the definition of Enum, I can only guess Enum is special-cased.
Still another option would be to pass an explicit type token for the return
type. We currently do not use the ability to return a different type, so
this would not require changing the call-sites if we did this:
public <T extends Artifact<? super T>> SortedSet<T> find(Class<T>
artifactType) {
return find(artifactType, artifactType);
}
public <A extends Artifact<? super A>, T extends Artifact<? super T>>
SortedSet<A> find(Class<A> returnType, Class<T> artifactType) {
...
}
Would that be preferable? It would make it harder to introduce something
that wouldn't compile on OpenJDK, as you would get a compile error and would
have to add a second type token if you tried to return a different type, and
it avoids having to infer the return type in all current uses.
2) What's the plan for preventing regressuions or new occurrences of this in
> the future?
>
I think when we upgrade our continuous build system, we should build with
OpenJDK. Until then, I can build with OpenJDK so whenever I build trunk it
would be noticed.
--
John A. Tamplin
Software Engineer (GWT), Google
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