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digitalmars.D.bugs - [Issue 9218] New: [2.061] Correct signature of struct opCmp no longer accepts enum structs

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=9218

           Summary: [2.061] Correct signature of struct opCmp no longer
                    accepts enum structs
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: rejects-valid
          Severity: regression
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: siegelords_abode yahoo.com



This code worked fine in 2.060, errors with 2.061 beta 1:

struct A
{
    enum zero = A(); // Error: A() is not an lvalue

    int opCmp(const ref A a) const
    //int opCmp(A a)
    {
        return 1;
    }
}

void main()
{
    A a;
    auto b = a > A.zero;
    assert(typeid(a).xopCmp !is null);
}

Obviously I could use a different signature for opCmp (e.g. the one I commented
out) but then the assert below will fail, as only the correct signature of
opCmp is accepted. Fixing either this bug or
http://d.puremagic.com/issues/show_bug.cgi?id=8561 would be good enough for me.

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next sibling parent d-bugmail puremagic.com writes:
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Andrej Mitrovic <andrej.mitrovich gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |andrej.mitrovich gmail.com



14:57:01 PST ---
Since it's a struct you can also use:

int opCmp()(auto const ref A a) const

Otherwise I don't think this is a rejects-valid, it's a documentation issue.
Struct literals (manifests included) are no longer lvalues in 2.061, this is by
design.

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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 Since it's a struct you can also use:
 
 int opCmp()(auto const ref A a) const


This fails the assert.


 Otherwise I don't think this is a rejects-valid, it's a documentation issue.
 Struct literals (manifests included) are no longer lvalues in 2.061, this is by
 design.


Then this bug highlights what a bad set of design decisions it was to both make
struct literals not lvalues AND require the proper opCmp signature to function
only for lvalues.

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SomeDude <lovelydear mailmetrash.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |lovelydear mailmetrash.com



PST ---
Tested on DPaste, this code runs successfully with DMD 2.x Git (UDA beta build)
(supposedly updated daily) both in 32 and 64 bits.

http://dpaste.dzfl.pl/fork/54f9a9e5

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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Walter Bright <bugzilla digitalmars.com> changed:

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



16:43:35 PST ---


 Tested on DPaste, this code runs successfully with DMD 2.x Git (UDA beta build)
 (supposedly updated daily) both in 32 and 64 bits.
 
 http://dpaste.dzfl.pl/fork/54f9a9e5


I haven't been able to open that link. In general, I think it's better to just
paste code examples inline here.

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16:51:22 PST ---
Solving the rvalue reference problem, Issue 9238, is the correct way to resolve
this. Unfortunately, I think it would be too disruptive to add such a large
change with potential side effects in at the last minute, so I'd like to defer
this to the next version.

In the meantime, you can workaround by providing an overload:

    int opCmp(const A a) { return 1; }

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bearophile_hugs eml.cc changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bearophile_hugs eml.cc





 I haven't been able to open that link.



The code:

struct A
{
    enum zero = A(); // Error: A() is not an lvalue

    int opCmp(const ref A a) const
    //int opCmp(A a)
    {
        return 1;
    }
}
void main()
{
    A a;
    auto b = a > A.zero;
    assert(typeid(a).xopCmp !is null);
}


test.d(3): Error: A() is not an lvalue

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I worked around this for now by adding this overload:

int opCmp(const A a) const
{
    return opCmp(a);
}

This seems to work because the compiler prefers the const ref version to the
const version.

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PST ---




 Tested on DPaste, this code runs successfully with DMD 2.x Git (UDA beta build)
 (supposedly updated daily) both in 32 and 64 bits.
 
 http://dpaste.dzfl.pl/fork/54f9a9e5


 
 I haven't been able to open that link. In general, I think it's better to just
 paste code examples inline here.


It's the code of the original problem description.
I copy it in DPaste because it offers a very convenient way to test it with the
three main D compilers in both 32 and 64 bits without having to install these
compilers on one's own computer. DPaste offers the 2.060 compilers as well as
the latest overnight version of the main branch, so it's quite convenient for
quick testing.

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Ok, that workabout is not quite complete (perhaps this is a different bug
now?). While it solves the code in the original comment, this code doesn't
work:

struct A
{
    enum A zero = {}; // Note the difference here

    int opCmp(const ref A a) const
    {
        return 1;
    }

    int opCmp(const A a) const
    {
        return opCmp(a);
    }
}

void main()
{
    A a;
    auto b = a >= A.zero; //The error is now here! test.d(21): Error: A() is
not an lvalue
    auto c = a > a;
    assert(typeid(a).xopCmp !is null);
    typeid(a).xopCmp(&a, &a);
}

Why would enum A zero = A(); work but enum A zero = {}; not work? Is it safe
(in terms of inadvertent GC usage) to use A() instead of {}?

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---


 Ok, that workabout is not quite complete (perhaps this is a different bug
 now?). While it solves the code in the original comment, this code doesn't
 work:
 


[snip]

 
 Why would enum A zero = A(); work but enum A zero = {}; not work? Is it safe
 (in terms of inadvertent GC usage) to use A() instead of {}?


This is a different bug which is unrelated to the ref-non-ref overloading.
I opened a new bug report.

Issue 9293 - enum struct with StructInitializer reports weird error

So this is an invalid bug, because:



 Struct literals (manifests included) are no longer lvalues in 2.061, this is by


design.

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prev sibling parent d-bugmail puremagic.com writes:
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Walter Bright <bugzilla digitalmars.com> changed:

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



15:28:53 PST ---
We still need to address the rvalue ref issue, but at the moment this is
invalid because it's by design.

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