session.scala

scala> trait B { def build: Int }
defined trait B

scala> case class B1() extends B { val build = 1 }
defined class B1

scala> case class B2() extends B { val build = 2 }
defined class B2

scala> val l: List[() => B] = List(B1, B2)
l: List[() => B] = List(B1, B2)

scala> case class B3(implicit i: Int) extends B { val build = i }
defined class B3

scala> val l2: List[() => B] = List(B1, B2, B3)
<console>:14: error: type mismatch;
 found   : B3.type (with underlying type object B3)
 required: () => B
       val l2: List[() => B] = List(B1, B2, B3)