https://issues.dlang.org/show_bug.cgi?id=14477

Justin Whear <justin@economicmodeling.com> changed:

           What    |Removed                     |Added
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           Keywords|                            |pull
             Status|NEW                         |ASSIGNED
                URL|                            |https://github.com/D-Progra
                   |                            |mming-Language/phobos/pull/
                   |                            |3213

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https://issues.dlang.org/show_bug.cgi?id=14477

MichaelZ <dlang.org@bregalad.de> changed:

           What    |Removed                     |Added
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                 CC|                            |dlang.org@bregalad.de

--- Comment #1 from MichaelZ <dlang.org@bregalad.de> ---
I see the pull-request from when this issue was filed was retracted, as this is evidently - in terms of implementation - a lot more subtle than it initially sounds.

Is it really still being worked on?

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https://issues.dlang.org/show_bug.cgi?id=14477

Justin Whear <justin@economicmodeling.com> changed:

           What    |Removed                     |Added
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             Status|ASSIGNED                    |NEW

--- Comment #2 from Justin Whear <justin@economicmodeling.com> ---
Afraid not.

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https://issues.dlang.org/show_bug.cgi?id=14477

--- Comment #3 from MichaelZ <dlang.org@bregalad.de> ---
This is currently an issue for us, and it has been proposed we use Algebraic!Foo instead, which appears to work sufficiently, see below.

What aspects are against doing it this way?
The implementation of Algebraic "looks" a lot more heavyweight, but is it
really, particularly in this very specific usage?
If we don't like the toString behaviour, or want to have .nullify, and prefer
.isNull to .hasValue, we can always make Nullable a pretty minimal wrapper...

Thoughts?

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import std.variant;
import std.stdio;
import std.string;

struct Foo
{
    int x;
    @disable this();
    this(int value) { x=value; }
}

void main()
{
     Algebraic!Foo foo;

     writeln("hasValue for default-initialized foo: %s".format(foo.hasValue));
     writeln("Format default-initialized foo: %s".format(foo));

     foo = Foo(5);

     writeln("hasValue for set foo: %s".format(foo.hasValue));
     writeln("Format set foo: %s".format(foo));

     foo = Algebraic!Foo();  // Nullable's foo.nullify is cooler :/

     writeln("hasValue for reset foo: %s".format(foo.hasValue));
     writeln("Format reset foo: %s".format(foo));
}

--- output ---

hasValue for unset foo: false
Format unset foo: <Uninitialized VariantN>
hasValue for set foo: true
Format set foo: Foo(5)
hasValue for unset foo: false
Format unset foo: <Uninitialized VariantN>

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https://issues.dlang.org/show_bug.cgi?id=14477

--- Comment #4 from MichaelZ <dlang.org@bregalad.de> ---
(In reply to MichaelZ from comment #3)
> This is currently an issue for us, and it has been proposed we use Algebraic!Foo instead, which appears to work sufficiently, see below.
> 
> What aspects are against doing it this way?

More than a year of working around the issue in various ways, I looked at the Algebraic thing again:  One disadvantage of Algebraic is that it doesn't have the same magical implicit .get behaviour as Nullable does :-|

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https://issues.dlang.org/show_bug.cgi?id=14477

--- Comment #5 from github-bugzilla@puremagic.com ---
Commit pushed to master at https://github.com/dlang/phobos

https://github.com/dlang/phobos/commit/61d53a1ad4a64cb5d3686c3e755bcb3508ef22f6
fix Issue 14477 - Nullable does not work with structs with default constructor
disabled
Add unittest, improve error message a bit.

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https://issues.dlang.org/show_bug.cgi?id=14477

github-bugzilla@puremagic.com changed:

           What    |Removed                     |Added
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             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

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https://issues.dlang.org/show_bug.cgi?id=14477

--- Comment #6 from github-bugzilla@puremagic.com ---
Commit pushed to stable at https://github.com/dlang/phobos

https://github.com/dlang/phobos/commit/61d53a1ad4a64cb5d3686c3e755bcb3508ef22f6 fix Issue 14477 - Nullable does not work with structs with default constructor disabled

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