Incorrect handling of `-source:3.5-migration` in implicits behaviour deprecation

[WojciechMazur]

Compiler version

3.5.0-RC1

Minimized code

//> using options -source:3.5-migration

final class StrictEqual[V]
final class Less[V]
type LessEqual[V] = Less[V] | StrictEqual[V]

object TapirCodecIron:
  trait ValidatorForPredicate[Value, Predicate]
  trait PrimitiveValidatorForPredicate[Value, Predicate]
      extends ValidatorForPredicate[Value, Predicate]

  given validatorForLessEqual[N: Numeric, NM <: N](using
      ValueOf[NM]
  ): PrimitiveValidatorForPredicate[N, LessEqual[NM]] = ???
  given validatorForDescribedOr[N, P](using
      IsDescription[P]
  ): ValidatorForPredicate[N, P] = ???

  trait IsDescription[A]
  object IsDescription:
    given derived[A]: IsDescription[A] = ???

@main def Test = {
  import TapirCodecIron.{*, given}
  type IntConstraint = LessEqual[3]
  summon[ValidatorForPredicate[Int, IntConstraint]]
}

Output

[error] ./tapir.repro.scala:24:52
[error] Ambiguous given instances: both given instance validatorForDescribedOr in object TapirCodecIron and given instance validatorForLessEqual in object TapirCodecIron match type TapirCodecIron.ValidatorForPredicate[Int, IntConstraint] of parameter x of method summon in object Predef
[error]   summon[ValidatorForPredicate[Int, IntConstraint]]
[error]                                                    ^
Error compiling project (Scala 3.5.0-RC1, JVM (17))

Expectation

Should yield warning as it does under -source:3.5

Compiling project (Scala 3.5.0-RC1, JVM (17))
[warn] ./tapir.repro.scala:24:52
[warn] Given search preference for TapirCodecIron.ValidatorForPredicate[Int, IntConstraint] between alternatives (TapirCodecIron.validatorForDescribedOr :
[warn]   [N, P]
[warn]     (using x$1: TapirCodecIron.IsDescription[P]):
[warn]       TapirCodecIron.ValidatorForPredicate[N, P]
[warn] ) and (TapirCodecIron.validatorForLessEqual :
[warn]   [N, NM <: N]
[warn]     (implicit evidence$1: Numeric[N], x$1: ValueOf[NM]):
[warn]       TapirCodecIron.PrimitiveValidatorForPredicate[N, LessEqual[NM]]
[warn] ) will change
[warn] Current choice           : the second alternative
[warn] New choice from Scala 3.6: none - it's ambiguous
[warn]   summon[ValidatorForPredicate[Int, IntConstraint]]
[warn]                                                    ^
Compiled project (Scala 3.5.0-RC1, JVM (17))

[WojciechMazur]

What's interesting is the fact that without any -source flag there is no warning/error at all.