http://d.puremagic.com/issues/show_bug.cgi?id=8902

           Summary: Unexpected "duplicate union initialization for X"
                    error
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: verylonglogin.reg@gmail.com


--- Comment #0 from Denis Shelomovskij <verylonglogin.reg@gmail.com> 2012-10-28 10:12:15 MSK ---
Should assigning `.init` to a union be allowed or disallowed? At leas current behavior is inconsistent:

---
union U { int a, b; }

enum U u0 = U.init;  // No errors
U u1;                // No errors
U u2 = U.init;  // Error: duplicate union initialization for b

void main()
{
    U u3 = U.init;            // No errors
    immutable U u4 = U.init;  // No errors
    immutable static U u5 = U.init;  // Error: duplicate union...
    static U u6 = u4;      // Error: duplicate union...
    static U u7 = U.init;  // Error: duplicate union...
}
---

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monarchdodra@gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |monarchdodra@gmail.com
           Severity|normal                      |major


--- Comment #1 from monarchdodra@gmail.com 2012-10-28 01:06:44 PDT ---
(In reply to comment #0)
> Should assigning `.init` to a union be allowed or disallowed? At leas current behavior is inconsistent:
> 
> ---
> union U { int a, b; }
> 
> enum U u0 = U.init;  // No errors
> U u1;                // No errors
> U u2 = U.init;  // Error: duplicate union initialization for b
> 
> void main()
> {
>     U u3 = U.init;            // No errors
>     immutable U u4 = U.init;  // No errors
>     immutable static U u5 = U.init;  // Error: duplicate union...
>     static U u6 = u4;      // Error: duplicate union...
>     static U u7 = U.init;  // Error: duplicate union...
> }
> ---

It would further more appear that the compiler has trouble detecting this in conditional implementations, which makes it difficult to bypass this problem.

//----
import std.stdio;

union U { int a, b; }

void main()
{
    static if (is(typeof((inout int _dummy=0){static U i = U.init;}))) //FINE
    {
        static U i = U.init; //L9: DERP
    }
}
//----
main.d(9): Error: duplicate union initialization for b
//----

Raising priority due to the impossibility to easily bypass this problem...

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--- Comment #2 from Denis Shelomovskij <verylonglogin.reg@gmail.com> 2012-10-28 12:12:11 MSK ---
(In reply to comment #1)
> (In reply to comment #0)
> It would further more appear that the compiler has trouble detecting this in
> conditional implementations, which makes it difficult to bypass this problem.

Possible this is related to an error gagging problem. E.g. consider this:
---
union U { int a, b; }

template t(T)
{ static T t = T.init; } // Error: duplicate union initialization for b

static if (__traits(compiles, t!U)) { }
---

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--- Comment #3 from github-bugzilla@puremagic.com 2012-12-12 07:41:20 PST ---
Commit pushed to master at https://github.com/D-Programming-Language/phobos

https://github.com/D-Programming-Language/phobos/commit/44310012fea6751561a852cc5ef4056a0ba9d272 Add note about Issue 8902 workaround

* Issue 8902 URL: http://d.puremagic.com/issues/show_bug.cgi?id=8902

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--- Comment #4 from github-bugzilla@puremagic.com 2012-12-13 04:57:44 PST ---
Commits pushed to master at https://github.com/D-Programming-Language/phobos

https://github.com/D-Programming-Language/phobos/commit/1c54f33603b00163c4736696f2e24587e024327d fixup for Issue 8902

After default initialization, only the first one in overlapped fields is readable in CTFE.

https://github.com/D-Programming-Language/phobos/commit/437f15689dae803510321185f3545479dee7c473 Merge pull request #1007 from 9rnsr/fix8902

fixup for Issue 8902

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--- Comment #5 from github-bugzilla@puremagic.com 2013-03-05 08:23:20 PST ---
Commits pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/840d88a6e539e9817cffdc4abe8ad6357897d54a fix Issue 8902 - Unexpected "duplicate union initialization for X" error

https://github.com/D-Programming-Language/dmd/commit/a975ed6aacd7e2604808a74fb509da99c10624ef Merge pull request #1369 from 9rnsr/fix8902

Issue 8902 - Unexpected "duplicate union initialization for X" error

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla@digitalmars.com
         Resolution|                            |FIXED


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