Expand type class operations on elements using macros

Question

Assuming the following setup:

trait A[L] { def op(l1:L, l2:L): L }
trait E[L] { def op(l:L): L }

implicit def some2E[L:A](self:L) =  new E[L] { def op(other:L) =      
  implicitly[A[L]].op(self,other) }

Is there a way to directly expand m op n to a.op(m,n), in a context where a is the appropriate implicit A, using macros or at least avoid the additional object creation?

Answer 1

If you move the implicit parameter to the op method, you can use a value class to prevent the additional object creation:

implicit class some2E[L](val self: L) extends AnyVal {
 def op(other: L)(implicit x: A[L]) = x.op(self, other)
}

Hotspot will probably inline the call to theop defined in some2E, so you will end up with a.op(m, n).