http://d.puremagic.com/issues/show_bug.cgi?id=9953

           Summary: manifest constants of reference types should be
                    illegal
           Product: D
           Version: D1 & D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: clugdbug@yahoo.com.au


--- Comment #0 from Don <clugdbug@yahoo.com.au> 2013-04-18 01:43:43 PDT ---
---
enum X = [1,2,3];

void main()
{
   assert( X.ptr is X.ptr);
   assert( X is X );
}
---
Both asserts fail at runtime, because they are equivalent to

   assert( [1,2,3].ptr is [1,2,3].ptr);
   assert( [1,2,3] is [1,2,3] );

It would be OK for X to be an int[3] array, but not a slice.
Fundamentally, a reference enum type doesn't make sense. They can't have an
address.
This is the root cause of bug 4397.

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bearophile_hugs@eml.cc changed:

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                 CC|                            |bearophile_hugs@eml.cc


--- Comment #1 from bearophile_hugs@eml.cc 2013-04-18 02:43:05 PDT ---
This bug report seems for associative arrays too, then.

This bug report is about an old and significant problem of D. Disallowing all enum reference types seems a little harsh, but I don't know if there are better solutions.

One problem with this proposal is that there is probably some D code around that uses enum dynamic arrays and associative arrays (I have stopped using them in my code since some time), and this proposal will break that code.

One advantage of disallowing enum dynamic arrays is that this avoids a performance trap, because they get rebuild at every usage point, and this in the middle of a loop is a waste of time.

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Andrej Mitrovic <andrej.mitrovich@gmail.com> changed:

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


--- Comment #2 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2013-04-18 07:15:52 PDT ---
If we're going to do this we might as well introduce it in 2.063, since this release will have breaking changes related to this.

For example const/immutable fields with initializers will no longer be implicitly static, and people might end up changing them to manifest constants. If they were l-value initializers it's going to cause further problems when this issue is implemented (hence why it should be done sooner rather than later to avoid fixing code two times).

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