Hi
On 4/30/25 12:51, Rowan Tommins [IMSoP] wrote:
I think you are insisting on a different definition of "private" for nested classes than
exists anywhere else in the language, and one that I've not seen evidence of in any other similar
language either. It seems you want members to be "hidden", such that you can't even know
they exist.
No, I don't think I'm using a different definition of "private" for
nested classes.
More specifically, you want their *fully-qualified name* to somehow be available for reuse. That's not how
private members of a class work - methods A::foo() and B::foo() have different fully-qualified names, as do
properties A::$foo and B::$foo, regardless of visibility and inheritance. It's not how "namespace
private", "module private", or "file private" classes would naturally work, because
they all would need to be referenceable with fully-qualified names within the scope where they were visible.
The difference is that for private class members there is no chance of
name collisions of the "fully-qualified" name, but there is for nested
classes as proposed in this RFC. There is no way for anyone except for
the author of the class `A` to create a property with the fully
qualified name `A::$foo`. Granted, properties could be inherited from a
parent class and might thus cause collisions with a private property in
a subclass. However the same collision would happen if the child class
would already have a public property of the same name. Importantly, the
child class could just rename its private property without any effect on
any other class and also parent classes can introduce private properties
without any effect on any other class.
This is difference for nested classes as proposed in this RFC, since the
namespace of nested classes is shared with the namespace of regular
classes and the namespace of regular classes is not “closed off” for
addition after the initial declaration.
It's also not a new problem: PHP doesn't enforce a file and directory layout, and
libraries can and do define things "inside" each other's namespaces. When
declaring a class, you have to be aware of whether a class with the same fully-qualified
name has been, or will be, declared in another file.
This is correct, but all these other classes that could conflict are
part of the *public API* of a library. But now with private nested
classes I would also be aware of the private part of a library to avoid
conflicts.
Best regards
Tim Düsterhus
