position of using clause prevents overloaded extension method being picked

Compiler version

3.0.0-RC1

Minimized code and output

extension [T1](x: T1)(using Numeric[T1])
  def combine[T2](y: T2)(using Numeric[T2]) = ???
  def combine(y: String) = ???

val res = 100.combine(200)
//        ^^^^^^^^^^^
//    value combine is not a member of Int.
//    An extension method was tried, but could not be fully constructed:
//
//        combine()    failed with
//
//            value combine: <overloaded combine> does not take parameters

Expectation : should work, as when we move using to the end of the parameter list:

extension [T1](x: T1)
  def combine[T2](y: T2)(using Numeric[T2], Numeric[T1]) = ???
  def combine(y: String) = ???

val res = 100.combine(200)

[rjolly]

What’s disturbing is that with non-extensions it succeeds:

def combine[T1,T2](x: T1)(using Numeric[T1])(y: T2)(using Numeric[T2]) = ???
def combine[T1](x: T1)(using Numeric[T1])(y: String) = ???

val res = combine(100)(200)

So it seems we’re not far from the goal.

[som-snytt]

Also extension with overload, using: https://github.com/lampepfl/dotty/issues/13668