Supports for named tuples

[MateuszKubuszok]

Discussed in #761

^{Originally posted by nedsociety July 14, 2025}
Since Scala 3.7 this is now enabled by default, so it'd be nice to have derivations available for named tuples <=> products transformation.

//> using scala 3.7.1
//> using dep io.scalaland::chimney:1.8.3
import io.scalaland.chimney.dsl.*

case class C(a: Int, b: Int)

(b=2, a=1).transformInto[C]

Currently it errors with missing derivation:

-- Error: ----------------------------------------------------------------------
1 |(b=2, a=1).transformInto[C]
  |                           ^
  |Chimney can't derive transformation from scala.NamedTuple.NamedTuple[scala.Tuple2["b", "a"], scala.Tuple2[scala.Int, scala.Int]] to rs$line$2.C
  |
  |rs$line$2.C
  |  a: scala.Int - no accessor named a in source type scala.NamedTuple.NamedTuple[scala.Tuple2["b", "a"], scala.Tuple2[scala.Int, scala.Int]]
  |  b: scala.Int - no accessor named b in source type scala.NamedTuple.NamedTuple[scala.Tuple2["b", "a"], scala.Tuple2[scala.Int, scala.Int]]
  |
  |Consult https://chimney.readthedocs.io for usage examples.
  |
1 error found

The issue seem to be this piece of code

chimney/chimney/src/main/scala/io/scalaland/chimney/internal/compiletime/derivation/transformer/rules/TransformProductToProductRuleModule.scala

Lines 78 to 81 in a55f1df

	val usePositionBasedMatching =
	Type[From].isTuple || Type[To].isTuple || ctx.config.filterCurrentOverridesForFallbacks.exists {
	case TransformerOverride.Fallback(runtimeData) => runtimeData.Underlying.isTuple
	}

It assumes that all tuples should be handled in position-based way, which does not work for named tuples. So named tuples would have to be excluded from this case. Then we can see whether NamedTuples methods are visible to macros.

Testing it might be tricky since 1.x is on 3.3, so they would have to be written on 2.0.0-development branch, and the solution would either have to be implemented on that branch, or ported to it.