Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Thursday, 30 August 2018 at 12:18:10 UTC, Elie Morisse wrote: On Monday, 11 June 2018 at 15:41:57 UTC, Steven Schveighoffer wrote: I filed a bug about a similar thing (calling private functions instead of using private variables), but it seemed to be agreed upon that this is expected behavior: https://issues.dlang.org/show_bug.cgi?id=15897 You may find some more insight from reading that discussion. I don't agree with the conclusion, as it is very surprising behavior to me. -Steve Not the same, bauss' case is a template method that wouldn't get the depreciation warning if it wasn't templated. Template instances not always having the same access privileges as their template declaration's is definitely a bug. Or actually since I didn't test the code it's more likely just due to T being Bar, in which case there's no reason to make the cast to Foo mandatory since Foo's field get accessed from Foo's method.
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Monday, 11 June 2018 at 15:41:57 UTC, Steven Schveighoffer wrote: I filed a bug about a similar thing (calling private functions instead of using private variables), but it seemed to be agreed upon that this is expected behavior: https://issues.dlang.org/show_bug.cgi?id=15897 You may find some more insight from reading that discussion. I don't agree with the conclusion, as it is very surprising behavior to me. -Steve Not the same, bauss' case is a template method that wouldn't get the depreciation warning if it wasn't templated. Template instances not always having the same access privileges as their template declaration's is definitely a bug.
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Monday, 11 June 2018 at 15:41:57 UTC, Steven Schveighoffer wrote: On 4/11/18 3:13 PM, bauss wrote: On Wednesday, 11 April 2018 at 17:58:25 UTC, Jonathan M Davis wrote: On Sunday, April 08, 2018 13:00:02 bauss via Digitalmars-d wrote: [...] I don't know. It could be argued either way. I think that the logic as to why [...] The thing is, it makes no sense why it shouldn't be legal since you can just cast to the base type, by that alone you're escaping the restriction that it's supposed to have. And it really goes against that private is module level. If it was module level then you should be able to access the member regardless of the reference to it. Just going through old messages on the NG. I filed a bug about a similar thing (calling private functions instead of using private variables), but it seemed to be agreed upon that this is expected behavior: https://issues.dlang.org/show_bug.cgi?id=15897 You may find some more insight from reading that discussion. I don't agree with the conclusion, as it is very surprising behavior to me. -Steve It goes against everything OOP and it goes against D's own private.
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On 4/11/18 3:13 PM, bauss wrote: On Wednesday, 11 April 2018 at 17:58:25 UTC, Jonathan M Davis wrote: On Sunday, April 08, 2018 13:00:02 bauss via Digitalmars-d wrote: [...] I don't know. It could be argued either way. I think that the logic as to why [...] The thing is, it makes no sense why it shouldn't be legal since you can just cast to the base type, by that alone you're escaping the restriction that it's supposed to have. And it really goes against that private is module level. If it was module level then you should be able to access the member regardless of the reference to it. Just going through old messages on the NG. I filed a bug about a similar thing (calling private functions instead of using private variables), but it seemed to be agreed upon that this is expected behavior: https://issues.dlang.org/show_bug.cgi?id=15897 You may find some more insight from reading that discussion. I don't agree with the conclusion, as it is very surprising behavior to me. -Steve
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Wednesday, 11 April 2018 at 17:58:25 UTC, Jonathan M Davis wrote: On Sunday, April 08, 2018 13:00:02 bauss via Digitalmars-d wrote: [...] I don't know. It could be argued either way. I think that the logic as to why [...] The thing is, it makes no sense why it shouldn't be legal since you can just cast to the base type, by that alone you're escaping the restriction that it's supposed to have. And it really goes against that private is module level. If it was module level then you should be able to access the member regardless of the reference to it.
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On 11.04.2018 19:58, Jonathan M Davis wrote: I don't know. It could be argued either way. Not really. bauss is right about this. https://en.wikipedia.org/wiki/Liskov_substitution_principle
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Sunday, April 08, 2018 13:00:02 bauss via Digitalmars-d wrote:
> On Sunday, 8 April 2018 at 10:48:19 UTC, user1234 wrote:
> > On Saturday, 7 April 2018 at 20:46:39 UTC, bauss wrote:
> >> On Saturday, 7 April 2018 at 20:34:57 UTC, user1234 wrote:
> >>> On Saturday, 7 April 2018 at 20:14:49 UTC, bauss wrote:
> >>>> jesus that became a long title.
> >>>>
> >>>> Anyway as the title says, is it a bug that a parent class
> >>>> that access its own private members from derived classes
> >>>> gets deprecation warning?
> >>>
> >>> If the import is selective no. (`import foo : Foo;`)
> >>> If the import is for the whole module i'd say yes. (`import
> >>> foo;`)
> >>
> >> What do you mean?
> >>
> >> The problem is that "Foo" cannot access "_baz" without
> >> deperecation warning, but "_baz" is a part of "Foo".
> >
> > _baz is private and not protected. The deprecation was
> > introduced because bug 314 broke the private protection.
>
> I think it's better demonstrated like this, because to me the
> behavior makes no sense.
>
> Especially since you can just cast "Bar" to "Foo" and then you're
> allowed to do it.
>
> Since we're inside Foo then it shouldn't care whether "_baz" is
> private or not.
>
> I could understand if the function was located within Bar, but
> it's not.
>
> It's perfectly normal in other languages that supports classes to
> access private members of parent's as long as you're within the
> parent's encapsulation.
>
> // a.d
> module a;
>
> class Foo
> {
> private:
> bool _baz;
>
> public:
> void handleBar(T : Foo)(T[] foos)
> {
> foreach (child; foos)
> {
> child._baz = true; // Not ok.
> (cast(Foo)child)._baz = true; // Ok.
> }
> }
> }
>
> // b.d
> module b;
>
> import a;
>
> class Bar : Foo
> {
>
> }
>
> // main.d
>
> module main;
>
> import b;
>
> void main()
> {
> auto bars = [new Bar, new Bar];
> auto bar = new Bar;
> bar.handleBar(bars);
> }
I don't know. It could be argued either way. I think that the logic as to
why
child._baz = true;
is not legal is because you're accessing it through a class reference that
does not have access to _baz, since it's private to the base class. Allowing
access to the base class member via a derived class reference arguably
violates private.
On the other hand, this is inside a member function of the base class, and
the base class has access to the private members - even if they're in an
object other than the current one. And by that logic, it should be legal to
access the base class member even though it's through a derived class
reference.
Usually, base classes don't handle any references for derived classes (they
may handle derived classes through base class references but not usually
through actual derived class references), and this sort of thing doesn't
come up. As such, I think that the obvious result would be the current
behavior regardless of whether that is actually the best behavior.
I suspect that this particular situation was never really thought through in
the implementation, but I don't know. And since I think that there are good
arguments in both directions, I really don't know whether the current
implementation is better or whether what you're trying to do should be
legal. Certainly, it seems like a valid enhancement request, though I have
no idea whether Walter would think that what you're trying to do should work
or not. I wouldn't be surprised either way.
- Jonathan M Davis
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Wednesday, 11 April 2018 at 17:20:23 UTC, martin wrote:
On Monday, 9 April 2018 at 17:16:56 UTC, bauss wrote:
On Monday, 9 April 2018 at 17:05:45 UTC, martin wrote:>>
Actually, this behaves as i would expect.
`_baz` is a private member of Foo (to be precise: it belongs
to module `a`)
in handleBar(), you iterate `Bar[]` - which is in module `b`.
By casting it to Foo, you are accessing the wanted module
(`a`) again.
but handleBar() is in a.
This behavior is allowed in ex. C#
`_baz` is a member of `module a : Foo` - `_baz`, as is
`handleBar()`.
`protected` is the Access specifier you want.
If i understand you correctly, you want it to behave as if
`_baz` would be a member of `handleBar()`
If this is really possible in C#, it lets my eyebrow raise.
Execute the following C# program and it will work just fine:
It's a really common pattern with OOP.
public class Foo
{
private string _baz;
public void HandleBar(Bar bar)
{
bar._baz = "Hello";
}
}
public class Bar : Foo
{
}
...
var bar = new Bar();
bar.HandleBar(bar);
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Wednesday, 11 April 2018 at 17:34:40 UTC, bauss wrote:
On Wednesday, 11 April 2018 at 17:20:23 UTC, martin wrote:
On Monday, 9 April 2018 at 17:16:56 UTC, bauss wrote:
On Monday, 9 April 2018 at 17:05:45 UTC, martin wrote:>>
Actually, this behaves as i would expect.
`_baz` is a private member of Foo (to be precise: it belongs
to module `a`)
in handleBar(), you iterate `Bar[]` - which is in module `b`.
By casting it to Foo, you are accessing the wanted module
(`a`) again.
but handleBar() is in a.
This behavior is allowed in ex. C#
`_baz` is a member of `module a : Foo` - `_baz`, as is
`handleBar()`.
`protected` is the Access specifier you want.
If i understand you correctly, you want it to behave as if
`_baz` would be a member of `handleBar()`
If this is really possible in C#, it lets my eyebrow raise.
Execute the following C# program and it will work just fine:
It's a really common pattern with OOP.
public class Foo
{
private string _baz;
public void HandleBar(Bar bar)
{
bar._baz = "Hello";
}
}
public class Bar : Foo
{
}
...
var bar = new Bar();
bar.HandleBar(bar);
Also protected is not the access modifier I want.
I only want to set it through the parent class and it should only
be used within the parent class.
But it's on each child passed to the parent class that it's set.
The children should NEVER touch the variable.
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Monday, 9 April 2018 at 17:16:56 UTC, bauss wrote: On Monday, 9 April 2018 at 17:05:45 UTC, martin wrote:>> Actually, this behaves as i would expect. `_baz` is a private member of Foo (to be precise: it belongs to module `a`) in handleBar(), you iterate `Bar[]` - which is in module `b`. By casting it to Foo, you are accessing the wanted module (`a`) again. but handleBar() is in a. This behavior is allowed in ex. C# `_baz` is a member of `module a : Foo` - `_baz`, as is `handleBar()`. `protected` is the Access specifier you want. If i understand you correctly, you want it to behave as if `_baz` would be a member of `handleBar()` If this is really possible in C#, it lets my eyebrow raise.
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Monday, 9 April 2018 at 17:05:45 UTC, martin wrote:
On Sunday, 8 April 2018 at 13:00:02 UTC, bauss wrote:
I think it's better demonstrated like this, because to me the
behavior makes no sense.
Especially since you can just cast "Bar" to "Foo" and then
you're allowed to do it.
Since we're inside Foo then it shouldn't care whether "_baz"
is private or not.
I could understand if the function was located within Bar, but
it's not.
It's perfectly normal in other languages that supports classes
to access private members of parent's as long as you're within
the parent's encapsulation.
// a.d
module a;
class Foo
{
private:
bool _baz;
public:
void handleBar(T : Foo)(T[] foos)
{
foreach (child; foos)
{
child._baz = true; // Not ok.
(cast(Foo)child)._baz = true; // Ok.
}
}
}
// b.d
module b;
import a;
class Bar : Foo
{
}
// main.d
module main;
import b;
void main()
{
auto bars = [new Bar, new Bar];
auto bar = new Bar;
bar.handleBar(bars);
}
Actually, this behaves as i would expect.
`_baz` is a private member of Foo (to be precise: it belongs to
module `a`)
in handleBar(), you iterate `Bar[]` - which is in module `b`.
By casting it to Foo, you are accessing the wanted module (`a`)
again.
but handleBar() is in a.
This behavior is allowed in ex. C#
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Sunday, 8 April 2018 at 13:00:02 UTC, bauss wrote:
I think it's better demonstrated like this, because to me the
behavior makes no sense.
Especially since you can just cast "Bar" to "Foo" and then
you're allowed to do it.
Since we're inside Foo then it shouldn't care whether "_baz" is
private or not.
I could understand if the function was located within Bar, but
it's not.
It's perfectly normal in other languages that supports classes
to access private members of parent's as long as you're within
the parent's encapsulation.
// a.d
module a;
class Foo
{
private:
bool _baz;
public:
void handleBar(T : Foo)(T[] foos)
{
foreach (child; foos)
{
child._baz = true; // Not ok.
(cast(Foo)child)._baz = true; // Ok.
}
}
}
// b.d
module b;
import a;
class Bar : Foo
{
}
// main.d
module main;
import b;
void main()
{
auto bars = [new Bar, new Bar];
auto bar = new Bar;
bar.handleBar(bars);
}
Actually, this behaves as i would expect.
`_baz` is a private member of Foo (to be precise: it belongs to
module `a`)
in handleBar(), you iterate `Bar[]` - which is in module `b`.
By casting it to Foo, you are accessing the wanted module (`a`)
again.
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Sunday, 8 April 2018 at 14:45:34 UTC, kdevel wrote:
On Sunday, 8 April 2018 at 13:00:02 UTC, bauss wrote:
[...]
// a.d
module a;
class Foo
{
private:
bool _baz;
public:
void handleBar(T : Foo)(T[] foos)
{
foreach (child; foos)
{
child._baz = true; // Not ok.
replace this line with
import std.stdio;
__PRETTY_FUNCTION__.writeln;
foos.writeln;
This writelns:
void a.Foo.handleBar!(Bar).handleBar(Bar[] foos)
[b.Bar, b.Bar]
So foos is actually an array of Bars. And there is no access
from a Bar to the private elements of it's baseclass Foo.
Yes, but we're in the module a and private is module level, so it
should be accessible from the function regardless of whether it's
Bar or not.
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Saturday, 7 April 2018 at 20:14:49 UTC, bauss wrote:
jesus that became a long title.
Anyway as the title says, is it a bug that a parent class that
access its own private members from derived classes gets
deprecation warning?
Scenario narrowed down:
// module foo;
class Foo
{
private:
bool _baz;
public:
final void foos(T : Foo)(string key, T[] values)
{
if (values && values.length)
{
foreach (child; values)
{
child._isChild = true;
}
}
}
}
// module bar;
class Bar : Foo
{
}
The above in my case will give a deprecation warning that
"_baz" isn't visible from "Bar".
Well, template has nothing to do with it. Also, private members
in D are private to the module, not to the class. Here's a
reduced example:
--- foo.d ---
import bar;
class Foo
{
private bool baz;
}
void test(Bar b)
{
b.baz = true;
}
--- bar.d ---
import foo;
class Bar : Foo {}
void main()
{
test(new Bar);
}
https://wiki.dlang.org/DIP22 mentions something called "look-up
origin"; the meaning of that term is unclear to me...
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On 08.04.2018 16:36, Timon Gehr wrote: On 08.04.2018 15:00, bauss wrote: It's perfectly normal in other languages that supports classes to access private members of parent's as long as you're within the parent's encapsulation. That is not true. Use 'protected'. Actually, I misunderstood your sentence. This is definitely a bug.
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Sunday, 8 April 2018 at 13:00:02 UTC, bauss wrote:
[...]
// a.d
module a;
class Foo
{
private:
bool _baz;
public:
void handleBar(T : Foo)(T[] foos)
{
foreach (child; foos)
{
child._baz = true; // Not ok.
replace this line with
import std.stdio;
__PRETTY_FUNCTION__.writeln;
foos.writeln;
This writelns:
void a.Foo.handleBar!(Bar).handleBar(Bar[] foos)
[b.Bar, b.Bar]
So foos is actually an array of Bars. And there is no access from
a Bar to the private elements of it's baseclass Foo.
What I am wondering about is why does the method template match
in the first place?
(cast(Foo)child)._baz = true; // Ok.
You also may use the ternary conditional operator for that (SCNR).
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On 08.04.2018 15:00, bauss wrote: It's perfectly normal in other languages that supports classes to access private members of parent's as long as you're within the parent's encapsulation. That is not true. Use 'protected'.
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Sunday, 8 April 2018 at 10:48:19 UTC, user1234 wrote:
On Saturday, 7 April 2018 at 20:46:39 UTC, bauss wrote:
On Saturday, 7 April 2018 at 20:34:57 UTC, user1234 wrote:
On Saturday, 7 April 2018 at 20:14:49 UTC, bauss wrote:
jesus that became a long title.
Anyway as the title says, is it a bug that a parent class
that access its own private members from derived classes
gets deprecation warning?
If the import is selective no. (`import foo : Foo;`)
If the import is for the whole module i'd say yes. (`import
foo;`)
What do you mean?
The problem is that "Foo" cannot access "_baz" without
deperecation warning, but "_baz" is a part of "Foo".
_baz is private and not protected. The deprecation was
introduced because bug 314 broke the private protection.
I think it's better demonstrated like this, because to me the
behavior makes no sense.
Especially since you can just cast "Bar" to "Foo" and then you're
allowed to do it.
Since we're inside Foo then it shouldn't care whether "_baz" is
private or not.
I could understand if the function was located within Bar, but
it's not.
It's perfectly normal in other languages that supports classes to
access private members of parent's as long as you're within the
parent's encapsulation.
// a.d
module a;
class Foo
{
private:
bool _baz;
public:
void handleBar(T : Foo)(T[] foos)
{
foreach (child; foos)
{
child._baz = true; // Not ok.
(cast(Foo)child)._baz = true; // Ok.
}
}
}
// b.d
module b;
import a;
class Bar : Foo
{
}
// main.d
module main;
import b;
void main()
{
auto bars = [new Bar, new Bar];
auto bar = new Bar;
bar.handleBar(bars);
}
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Saturday, 7 April 2018 at 20:14:49 UTC, bauss wrote: The above in my case will give a deprecation warning that "_baz" isn't visible from "Bar". Seems like a bug to me since I'm accessing "_baz" from "Foo" itself and not from "Bar" or is it by design that you can't do such thing. I would say that you are accessing it from Bar. Or maybe that should be "via Bar". You are in Foo, but with a reference to a Bar instance. And trying to get to the _baz that is in that Bar instance. But your design doesn't allow (or at least I would have thought it was an error, not warning) or want Bar objects to be able to access _baz.
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Saturday, 7 April 2018 at 20:46:39 UTC, bauss wrote: On Saturday, 7 April 2018 at 20:34:57 UTC, user1234 wrote: On Saturday, 7 April 2018 at 20:14:49 UTC, bauss wrote: jesus that became a long title. Anyway as the title says, is it a bug that a parent class that access its own private members from derived classes gets deprecation warning? If the import is selective no. (`import foo : Foo;`) If the import is for the whole module i'd say yes. (`import foo;`) What do you mean? The problem is that "Foo" cannot access "_baz" without deperecation warning, but "_baz" is a part of "Foo". _baz is private and not protected. The deprecation was introduced because bug 314 broke the private protection.
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Saturday, 7 April 2018 at 20:34:57 UTC, user1234 wrote: On Saturday, 7 April 2018 at 20:14:49 UTC, bauss wrote: jesus that became a long title. Anyway as the title says, is it a bug that a parent class that access its own private members from derived classes gets deprecation warning? If the import is selective no. (`import foo : Foo;`) If the import is for the whole module i'd say yes. (`import foo;`) What do you mean? The problem is that "Foo" cannot access "_baz" without deperecation warning, but "_baz" is a part of "Foo".
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Saturday, 7 April 2018 at 20:46:39 UTC, bauss wrote: The problem is that "Foo" cannot access "_baz" without deperecation warning, but "_baz" is a part of "Foo". I'm not trying to access "_baz" directly from "Bar" except for that I call the templated function that access "_baz", but that function is a part of "Foo"
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Saturday, 7 April 2018 at 20:14:49 UTC, bauss wrote: jesus that became a long title. Anyway as the title says, is it a bug that a parent class that access its own private members from derived classes gets deprecation warning? If the import is selective no. (`import foo : Foo;`) If the import is for the whole module i'd say yes. (`import foo;`)
Re: Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
On Saturday, 7 April 2018 at 20:14:49 UTC, bauss wrote:
foreach (child; values)
{
child._isChild = true;
}
I forgot: _isChild should be _baz in the narrowed down version.
Is it a bug that a parent class that access its own private members from derived classes gets deprecation warning?
jesus that became a long title.
Anyway as the title says, is it a bug that a parent class that
access its own private members from derived classes gets
deprecation warning?
Scenario narrowed down:
// module foo;
class Foo
{
private:
bool _baz;
public:
final void foos(T : Foo)(string key, T[] values)
{
if (values && values.length)
{
foreach (child; values)
{
child._isChild = true;
}
}
}
}
// module bar;
class Bar : Foo
{
}
The above in my case will give a deprecation warning that "_baz"
isn't visible from "Bar".
Seems like a bug to me since I'm accessing "_baz" from "Foo"
itself and not from "Bar" or is it by design that you can't do
such thing.
I'm thinking it's because of my templated function perhaps?
I haven't decoupled it out of my project to make a separate
compilation, I just want to clarify it's not a design thing
first, because if it's by design then I don't want to spend more
time on it than necessary.
If it's not by design then I'll narrow it down even more, to see
if it's reproducable as above.
(I did not test the narrowed down version.)
