Re: When are scala macros expanded?

Hi Jeremy

Without having spent much time trying to come up with a creative approach, 
I would be surprised if what you're trying to do were possible.

If I understand your problem statement correctly, you're trying to add a 
condition to a method defined on an interface "after the fact:" an 
additional (implicit) parameter, in this case. Yet this condition is only 
supposed to be checked for by the compiler if the implementation class of 
the interface happens to be *your* specific class. Which would seem to 
require that the compiler know up front what the *runtime* class of the 
implementation will be.

If I write:

val myObj: SomeInterface = ...
myObj.foo(...)

I would imagine that the compiler can *only* verify that my attempt to call 
foo is compatible with the definition of foo in SomeInterface, i.e. the 
static type of myObj. I don't see how, at compile time, we would be able to 
say: "Ah, if myObj in this case happens to be an instance of 
SpecialImplOfSomeInterface, we need to check for an extra 
implicit/parameter/parameter list/whatever."

Curious to see what other participants in this thread will come up with!

Regards

ap

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