Compiling with unknown class gives no error

[Duarte]

On Monday, 17 March 2014 at 22:44:00 UTC, bearophile wrote:
> Duarte:
>
>> Compiling this with dmd/ldc will procude no error whatsoever, 
>> not even a warning (with -w/-wi enabled). It will only trigger 
>> a compile error if the operator is called at some point.
>>
>> How come? Obviously if the class does not exist the compiler 
>> shouldn't be able to determine the return value of the 
>> overloaded operator.
>
> Similar questions are better asked in D.learn.
>
> opBinary is not a method, it's a method template. So until you 
> instantiate it, it doesn't actually exist. For some reasons for 
> templates like C++/D ones you can't perform a full analysis of 
> un-instantiated templated code. Time ago some people have asked 
> for a partial analysis of template code, but Andrei was against 
> it.
>
> Extra note: don't end D class definitions (and structs/enums) 
> with a semicolon.
>
> Bye,
> bearophile

Fair enough. Thanks dude!