[dart-misc] Overriding fields in strong mode

['Samuel Rawlins' via Dart Misc]

Hey Dart strong mode experts,

I am wondering why we cannot override fields in strong mode (without
changing type). Take this example:

class A {
int a;
}

class B extends A {
@deprecated
int a;
}

https://dartpad.dartlang.org/69bf3a7802e742e87a9c82b7a641a30a

yields the error: "Field declaration A.a cannot be overridden in B."

I think there are probably many reasons to want to annotate a field from
your super class (mark it @deprecated, or to observe it, or declare it
non-null, etc), and the only way to annotate it is to re-declare it.

A) Why can we not re-declare a field, if we don't change it's type or
access?
B) How else might you annotate a field in your super class?

[Frank Pepermans]

Never used the annotation myself, but did you try @virtual?
https://github.com/dart-lang/sdk/issues/27384

On Sat, 11 Mar 2017, 01:04 'Samuel Rawlins' via Dart Misc, <

Post by 'Samuel Rawlins' via Dart Misc
Hey Dart strong mode experts,
I am wondering why we cannot override fields in strong mode (without
class A {
int a;
}
class B extends A {
@deprecated
int a;
}
https://dartpad.dartlang.org/69bf3a7802e742e87a9c82b7a641a30a
yields the error: "Field declaration A.a cannot be overridden in B."
I think there are probably many reasons to want to annotate a field from
non-null, etc), and the only way to annotate it is to re-declare it.
A) Why can we not re-declare a field, if we don't change it's type or
access?
B) How else might you annotate a field in your super class?
--
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['Samuel Rawlins' via Dart Misc]

That is almost what I'm looking for, Frank. Thanks for the tip.

However, I'm looking at the issue where you don't control/own the super
class. In particular if you are extending dart:html's Element, or something
really distant from your code, in a separate package.

Here's the announcement:
https://github.com/dart-lang/sdk/blob/master/CHANGELOG.md#strong-mode-1

Post by Frank Pepermans
https://github.com/dart-lang/sdk/issues/27384
On Sat, 11 Mar 2017, 01:04 'Samuel Rawlins' via Dart Misc, <

Post by 'Samuel Rawlins' via Dart Misc
Hey Dart strong mode experts,
I am wondering why we cannot override fields in strong mode (without
class A {
int a;
}
class B extends A {
@deprecated
int a;
}
https://dartpad.dartlang.org/69bf3a7802e742e87a9c82b7a641a30a
yields the error: "Field declaration A.a cannot be overridden in B."
I think there are probably many reasons to want to annotate a field from
non-null, etc), and the only way to annotate it is to re-declare it.
A) Why can we not re-declare a field, if we don't change it's type or
access?
B) How else might you annotate a field in your super class?
--
For other discussions, see https://groups.google.com/a/dartlang.org/
For HOWTO questions, visit http://stackoverflow.com/tags/dart
To file a bug report or feature request, go to http://www.dartbug.com/new
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--
For other discussions, see https://groups.google.com/a/dartlang.org/
For HOWTO questions, visit http://stackoverflow.com/tags/dart
To file a bug report or feature request, go to http://www.dartbug.com/new
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['Vijay Menon' via Dart Misc]

FYI - this is slated to be supported again in 1.23 (overriding without
virtual):

https://github.com/dart-lang/sdk/issues/28117

That said, in your example below, instances of type B will end up with two
field slots for 'a', which might not be what you want.

On Fri, Mar 10, 2017 at 4:44 PM, 'Samuel Rawlins' via Dart Misc <

Post by 'Samuel Rawlins' via Dart Misc
That is almost what I'm looking for, Frank. Thanks for the tip.
However, I'm looking at the issue where you don't control/own the super
class. In particular if you are extending dart:html's Element, or something
really distant from your code, in a separate package.
Here's the announcement: https://github.com/dart-lang/sdk/blob/master/
CHANGELOG.md#strong-mode-1

Post by Frank Pepermans
https://github.com/dart-lang/sdk/issues/27384
On Sat, 11 Mar 2017, 01:04 'Samuel Rawlins' via Dart Misc, <

Post by 'Samuel Rawlins' via Dart Misc
Hey Dart strong mode experts,
I am wondering why we cannot override fields in strong mode (without
class A {
int a;
}
class B extends A {
@deprecated
int a;
}
https://dartpad.dartlang.org/69bf3a7802e742e87a9c82b7a641a30a
yields the error: "Field declaration A.a cannot be overridden in B."
I think there are probably many reasons to want to annotate a field from
non-null, etc), and the only way to annotate it is to re-declare it.
A) Why can we not re-declare a field, if we don't change it's type or
access?
B) How else might you annotate a field in your super class?
--
For other discussions, see https://groups.google.com/a/dartlang.org/
For HOWTO questions, visit http://stackoverflow.com/tags/dart
To file a bug report or feature request, go to
http://www.dartbug.com/new
---
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Groups "Dart Misc" group.
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--
For other discussions, see https://groups.google.com/a/dartlang.org/
For HOWTO questions, visit http://stackoverflow.com/tags/dart
To file a bug report or feature request, go to http://www.dartbug.com/new
---
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--
For other discussions, see https://groups.google.com/a/dartlang.org/
For HOWTO questions, visit http://stackoverflow.com/tags/dart
To file a bug report or feature request, go to http://www.dartbug.com/new
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