This compiles, but produces some strange output on the cmd line (DMD 0.150, Windows XP SP2):

interface ICollection(T) {
  int length();
}

interface IMap(TKey, TValue) {
  ICollection!(TKey) keys();
}

class Map(TKey, TValue) : IMap!(TKey, TValue) {
  KeyCollection keys() {
    return new KeyCollection;
  }
  class KeyCollection : ICollection!(TKey) {
    int length() {
      return 5;
    }
  }
}

void main() {
    IMap!(int, int) map = new Map!(int, int);
    writefln(map.keys.length);
}

Output:
KeyCollection
10227584

Why does it output "KeyCollection"? Is it some kind of runtime error? And why is map.keys.length not 5?

It's a forward reference problem. Try reversing the declarations of keys() and KeyCollection.

"Walter Bright" <newshound@digitalmars.com> wrote in message news:e09vmu$2ubc$1@digitaldaemon.com...
> It's a forward reference problem. Try reversing the declarations of keys() and KeyCollection.

Thanks - that fixed it.

But surely it highlights a separate bug: forward referencing isn't supposed to be an issue in D, is it?

John.

John C wrote:
> "Walter Bright" <newshound@digitalmars.com> wrote in message news:e09vmu$2ubc$1@digitaldaemon.com...
>> It's a forward reference problem. Try reversing the declarations of keys() and KeyCollection.
> 
> Thanks - that fixed it.
> 
> But surely it highlights a separate bug: forward referencing isn't supposed to be an issue in D, is it?

Correct.

You'll notice that many forward reference bugs have been filed both here and in DStress.  But a forward reference bug that leads to bad code generation is a new one on me.

Stewart.

-- 
-----BEGIN GEEK CODE BLOCK-----
Version: 3.1
GCS/M d- s:-@ C++@ a->--- UB@ P+ L E@ W++@ N+++ o K-@ w++@ O? M V? PS- PE- Y? PGP- t- 5? X? R b DI? D G e++>++++ h-- r-- !y
------END GEEK CODE BLOCK------

My e-mail is valid but not my primary mailbox.  Please keep replies on the 'group where everyone may benefit.

John C wrote:
> "Walter Bright" <newshound@digitalmars.com> wrote in message news:e09vmu$2ubc$1@digitaldaemon.com...
>> It's a forward reference problem. Try reversing the declarations of keys() and KeyCollection.
> 
> Thanks - that fixed it.
> 
> But surely it highlights a separate bug: forward referencing isn't supposed to be an issue in D, is it?

Looking at your code again, it appears to be a case of

http://d.puremagic.com/bugzilla/show_bug.cgi?id=65

I've just noticed that my testcase contains a forward reference as well.   Guess I'll have to try rewriting it without the forward reference and see what happens.

Stewart.

-- 
-----BEGIN GEEK CODE BLOCK-----
Version: 3.1
GCS/M d- s:-@ C++@ a->--- UB@ P+ L E@ W++@ N+++ o K-@ w++@ O? M V? PS- PE- Y? PGP- t- 5? X? R b DI? D G e++>++++ h-- r-- !y
------END GEEK CODE BLOCK------

My e-mail is valid but not my primary mailbox.  Please keep replies on the 'group where everyone may benefit.

"John C" <johnch_atms@hotmail.com> wrote in message news:e0avij$1bpj$1@digitaldaemon.com...
> But surely it highlights a separate bug: forward referencing isn't supposed to be an issue in D, is it?

Generally, it isn't. But the internal semantic routines need to be reorganized/reimplemented to do this better, and I'm not up for that right now.