https://issues.dlang.org/show_bug.cgi?id=11044

Andrei Alexandrescu <andrei@erdani.com> changed:

           What    |Removed                     |Added
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            Version|unspecified                 |D2

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https://issues.dlang.org/show_bug.cgi?id=11044

Nick Treleaven <nick@geany.org> changed:

           What    |Removed                     |Added
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           Keywords|                            |safe
                 CC|                            |nick@geany.org

--- Comment #2 from Nick Treleaven <nick@geany.org> ---
With dmd 2.074, -dip1000 the `dg = { return i; }` from comment 1 won't compile, but the original lazy code still does.

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https://issues.dlang.org/show_bug.cgi?id=11044

Carsten Blüggel <chilli@posteo.net> changed:

           What    |Removed                     |Added
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                 CC|                            |chilli@posteo.net

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https://issues.dlang.org/show_bug.cgi?id=11044

Vladimir Panteleev <dlang-bugzilla@thecybershadow.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
            Summary|Escaping references to lazy |Escaping references to lazy
                   |argument are allowed        |argument are allowed and
                   |                            |compile to wrong code
           Severity|normal                      |critical

--- Comment #3 from Vladimir Panteleev <dlang-bugzilla@thecybershadow.net> ---
Another test case:

///////////// test.d ////////////
@safe:

auto toDg(E)(lazy E value)
{
    return { return value; };
}

C t;

class C
{
    auto getDg()
    {
        // return () => prop;
        return toDg(prop);
    }

    final @property string prop()
    {
        assert(this is t);
        return null;
    }
}

void smashStack() {
    int[1024] dummy = 0xcafebabe;
}


void main()
{
    t = new C();
    auto result = t.getDg();
    smashStack();
    result();
}
/////////////////////////////////

The compiler needs to either reject the code (accepts-invalid), or generate a
closure (wrong-code).

Upgrading severity as this can manifest as a latent bug (depending on whether the stack was overwritten or not) in @safe code.

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https://issues.dlang.org/show_bug.cgi?id=11044

ag0aep6g <ag0aep6g@gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |simen.kjaras@gmail.com

--- Comment #4 from ag0aep6g <ag0aep6g@gmail.com> ---
*** Issue 19880 has been marked as a duplicate of this issue. ***

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https://issues.dlang.org/show_bug.cgi?id=11044

Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
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                 CC|                            |bugzilla@digitalmars.com

--- Comment #5 from Walter Bright <bugzilla@digitalmars.com> ---
I have a dip in the works to deprecate lazy parameters, replacing them with delegates, precisely because of problems like this. So this particular issue will likely not get fixed.

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https://issues.dlang.org/show_bug.cgi?id=11044

--- Comment #6 from Walter Bright <bugzilla@digitalmars.com> ---
I recommend in the meantime replacing the lazy parameter with a delegate.

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https://issues.dlang.org/show_bug.cgi?id=11044

RazvanN <razvan.nitu1305@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |razvan.nitu1305@gmail.com
         Resolution|---                         |WONTFIX

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https://issues.dlang.org/show_bug.cgi?id=11044

Adam D. Ruppe <destructionator@gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |destructionator@gmail.com

--- Comment #7 from Adam D. Ruppe <destructionator@gmail.com> ---
lazy lowers to delegate, so it should be easy to just lower to the right kind of delegate and get correct behavior. There was a dconf online talk about this in 2022.

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https://issues.dlang.org/show_bug.cgi?id=11044

Vladimir Panteleev <dlang-bugzilla@thecybershadow.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
                 CC|                            |dlang-bugzilla@thecybershad
                   |                            |ow.net
         Resolution|WONTFIX                     |---

--- Comment #8 from Vladimir Panteleev <dlang-bugzilla@thecybershadow.net> ---
(In reply to Walter Bright from comment #5)
> I have a dip in the works to deprecate lazy parameters, replacing them with delegates, precisely because of problems like this. So this particular issue will likely not get fixed.

Looks like this was not an easy decision to make, as the situation is unchanged three years later. I think we should at least do something about bugs like this in the meantime - the compiler should either reject such constructs or not generate bad code for them.

Personally I am skeptical that lazy can be removed from the language at this point, because for one thing doing so will break std.exception.enforce, and make it impossible to wrap or implement assert in user code. As far as I can see, we have no choice but to support it as part of the language going forward.

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