[Since version 2.13.0]Use explicit Equiv.universal instead. See Scaladoc entry for more information: ".+("https://www.scala-lang.org/api/current/scala/math/Equiv$.html#universalEquiv[T]:scala.math.Equiv[T]")This implicit universalEquiv instance allows accidentally comparing instances of types for which equality isn't well-defined or implemented. (For example, it does not make sense to compare twoFunction1 instances.) UseEquiv.universal explicitly instead. If you really want an implicit universalEquiv instance despite the potential problems, considerimplicit def universalEquiv[T]: Equiv[T] = universal[T].