Function Arguments of named tuples can't infer param types despite explicit type about scala3 HOT 4 CLOSED

(foo =  _.length) : (foo: String => Int)

NamedTuple.withNames(Tuple1(_.length))[Tuple1["foo"]] : (foo: String => Int)
//                          ^^^^^^^^
//                          nested lambda with no expected type

(NamedTuple.withNames(Tuple1(_.length): <watch[target]>)[Tuple1["foo"]] : <target>) : (foo: String => Int)

  extension [V <: Tuple](x: V)
    inline def withNames[N <: Tuple]: NamedTuple[N, V] = x

NamedTuple.withNames[V](tuple)[N]

def build[N <: Tuple]()[V <: Tuple](x: V): NamedTuple[N, V]

object NamedTupleBuilder {
  opaque type Builder[N <: Tuple] = Unit
  def apply[N <: Tuple]: Builder[N] = ()
}
extension [N <: Tuple](inline b: NamedTupleBuilder.Builder[N])
  transparent inline def build[V <: Tuple](inline v: V): NamedTuple[N, V] = v.withNames[N]

val m: (foo: String => Int, bar: String => Int) =
  (foo = _.length, bar = _.length)

val m: (foo: String => Int, bar: String => Int) =
  NamedTupleBuilder.apply[("foo", "bar")].build((_.length, _.length))

scala> val m: (foo: String => Int, bar: String => Int) = NamedTupleBuilder.apply[("foo", "bar")].build((_.length, _.length))
[[syntax trees at end of                     typer]] // rs$line$5
package <empty> {
  final lazy module val rs$line$5: rs$line$5 = new rs$line$5()
  final module class rs$line$5() extends Object() { this: rs$line$5.type =>
    val m: (foo : String => Int, bar : String => Int) =
      NamedTuple.withNames[(String => Int, String => Int)](
        Tuple2.apply[String => Int, String => Int](
          {
            def $anonfun(_$1: String): Int = _$1.length()
            closure($anonfun)
          },
          {
            def $anonfun(_$2: String): Int = _$2.length()
            closure($anonfun)
          }
        )
      )[(("foo" : String), ("bar" : String))]
  }
}

val m: (foo : String => Int, bar : String => Int) = (rs$line$5$$$Lambda$2022/0x000000012d6005d8@5e08ed28,rs$line$5$$$Lambda$2023/0x000000012d6009a8@24b05292)