On 06/12/2019 22:28, Brian Goetz wrote:
package java.util;
public class IdentityHashMap<E extends IdentityObject> { ... }
This one has an easy out:
public class IdentityHashMap<E extends Object&IdentityObject> { ... }
I was hoping your example would be type bounds, since they're easily
amenable to this trick (either explicitly, or with compiler help.) Got
more?
Uhm - doing this change is certainly binary compatible (the extra bound
is erased) - but it's not source compatible - every client using
IdentityHashMap<Object, ...> would fail to compile now, right?
E.g. imagine code like this:
public class Foo {
public Map<Object, String> cache = new IdentityHashMap<>();
}
With the proposed bound change, two things will happen:
1) the inferred type of the 'new' expression will change
2) the inferred type as of (1) will be incompatible with the type in the
LHS -> error
To fix the issue, you have to change the LHS type - if this is a public
API, this will then trigger more downstream issues (again, not about BC,
but about source compatibility).
Maurizio
