Support Mirrors for case classes with implicits

[dwijnand]

Minimized code

case class WithImplicit1(pos: Int, text: String)(implicit x: Numeric[Int]) { def x1 = x.one }

Output

scala> import scala.compiletime._, scala.deriving._

scala> val m = summon[Mirror.Of[WithImplicit1]]
1 |val m = summon[Mirror.Of[WithImplicit1]]
  |                                        ^
  |no implicit argument of type deriving.Mirror.Of[WithImplicit1] was found for parameter x of method summon in object Predef

Expectation

I expect a Mirror.Product exists for such a class.

[bishabosha]

linkind to #9985 which was closed in favour of status quo

[bishabosha]

I believe that mirror product only supports a single parameter list due to the need to implement the Mirror.Product.fromProduct method which is implemented based on the shape of that single parameter list.

Here the specification requires a single parameter list:

https://github.com/lampepfl/dotty/blob/609d8d6bdbe9be33080967cdac478a6957237356/compiler/src/dotty/tools/dotc/transform/SymUtils.scala#L81

[Lasering]

Related: #17777