Comment #0 by pro.mathias.lang — 2020-02-05T04:32:04Z
Code example:
```
class Channel (T) {}
interface Scheduler
{
void spawn (T) (Channel!T chan);
}
class ThreadScheduler : Scheduler
{
override void spawn (T) (Channel!T chan) { }
}
void main ()
{
Scheduler ths = new ThreadScheduler;
ths.spawn(new Channel!int);
}
```
This will lead to a link error with DMD 2.090.0:
```
Undefined symbols for architecture x86_64:
"__D3bug9Scheduler__T5spawnTiZQjMFCQBf__T7ChannelTiZQlZv", referenced from:
__Dmain in bug.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Error: linker exited with status 1
```
There are several problem here:
1) Having a templated method declaration without definition in an interface is odd. There can be a use case, e.g. for `extern` declarations, but those are marked as `extern`. But that's still open to discussion.
2) However, the `override void spawn` is completely wrong: the compiler should give the usual "Cannot override non-virtual method" error.
Another example:
```
class Channel (T) {}
interface Scheduler
{
void spawn (T) (Channel!T chan) { assert(0); }
}
class ThreadScheduler : Scheduler
{
override void spawn (T) (Channel!T chan) { }
}
void main ()
{
Scheduler ths = new ThreadScheduler;
ths.spawn(new Channel!int);
}
```
This triggers the assertion, because `Scheduler.spawn` is called (as it should), however users would expect `ThreadScheduler.spawn` to be called.
Comment #1 by robert.schadek — 2024-12-13T19:07:01Z