Code review request for 4881419 The type of X[].clone() should be X[]

[Jeroen Frijters]

Sorry to be late with my comment, but as a VM implementer I can't really agree with this modification. The return type of X[].clone() is clearly Object, not X{]. That illusion is a javac compiler trick. IMHO it belongs in the JLS not in the Object.clone() documentation.

Regards,
Jeroen

> -----Original Message-----
> From: core-libs-dev-bounces at openjdk.java.net [mailto:core-libs-dev-
> bounces at openjdk.java.net] On Behalf Of Joe Darcy
> Sent: Saturday, September 04, 2010 12:01 AM
> To: Martin Buchholz
> Cc: core-libs-dev
> Subject: Re: Code review request for 4881419 The type of X[].clone()
> should be X[]
> 
> Martin Buchholz wrote:
> >
> >
> > On Thu, Sep 2, 2010 at 17:50, Joe Darcy <joe.darcy at oracle.com
> > <mailto:joe.darcy at oracle.com>> wrote:
> >
> >     Martin Buchholz wrote:
> >
> >         The usage T[] suggests that T is a reference type, as with
> >         generics, which is not the case here.
> >
> >         More precisely, both the runtime types and compiletime types
> >         of the object returned from clone of any array is identical to
> >         its input.
> >         Is there a non-confusing way of saying that?
> >
> >
> >     How about
> >
> >     "...and that the return type of the {@code clone} method of an
> >     array type {@code T[]} is {@code T[]} where T is either a
> >     reference or a primitive type."?
> >
> >
> > So I went and actually read the Object.clone spec, and it does indeed
> > guarantee that the (runtime) class of the returned value is the same
> > as the class of the argument, for arrays.  As for the compile-time
> > type, an experiment demonstrates that the return type is indeed
> > exactly the same, including for non-reifiable array element types,
> > e.g. this compiles:
> >
> >         Class<? extends Number>[] a
> >             = (Class<? extends Number>[]) (new Class<?>[42]);
> >         Class<? extends Number>[] clone = a.clone();
> >
> >
> > So Ulf's restriction to non-reifiable T seems not to be correct.
> >
> > My suggested wording is:
> >
> > "...and that the return type of the {@code clone} method of an array
> > type {@code T[]} is {@code T[]} where T is any reference or primitive
> > type."
> >
> > Martin "Objects have class; Variables have type"
> 
> Sounds good to me; change pushed!
> 
> Thanks,
> 
> -Joe