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Urk.
> This made me think that specifying a '+' on the type pattern in the
case of
> 'extends <class>' should be regarded as an error ?
> Is there any case when it would actually make sense?
A use-case for
declare parents: T+ extends C;
is an opt-in tag interface, as in "declare that your class implements
interface T and everything will be handled for you"
More generally, hierarchy-dependent semantics seem
to conflict with per-class
weaving. Does the same problem not exist when declaring a member
of an interface,
and we encounter a subclass before the superclass?
We could weave supertypes before subtypes, but that wouldn't handle
situations
where the subtype is in an earlier weave process (not that we provide
any
guarantees when doing separate weaves of related classes). Does
that solve
this?
Wes
------------Original Message------------
From: Andrew Clement <CLEMAS@xxxxxxxxxx>
To: aspectj-dev@xxxxxxxxxxx
Date: Tue, Aug-24-2004 8:15 AM
Subject: [aspectj-dev] Declare parents extends quirk ?
Comments?
Here is a simple set of types
I have in a source file:
=========================
class
X { }
class SubX extends X {
}
aspect A {
declare parents: X+ extends
java.util.Observable;
}
=========================
(Note the inclusion of the + on the type
pattern).
if I compile it, it
succeeds and X now extends Observable (SubX does not because X does)
Now, if I switch it to this (order of
types switched):
=========================
class
SubX extends X { }
class X {
}
aspect A {
declare parents: X+ extends
java.util.Observable;
}
=========================
And compile it, I get:
============
C:\ajbugs\p\A.java:6 error can only insert a class into
hierarchy, but java.util.Observable is not a subtype of X
declare parents: X+ extends
java.util.Observable;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1 error
============
It is because
this time the compiler encountered 'SubX' first, which matched 'X+' - it then
barfed because we could not insert Observable into the hierarchy, as
Observable does not extend X.
This made me think that specifying a '+' on the type pattern in the
case of 'extends <class>' should be regarded as an error ? Is
there any case when it would actually make sense?
Andy.
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