scalaのリフレクションで、コンストラクタの有無を確認するコード

hasCtor.scala

import scala.reflect.runtime.universe._

class TypeCheck[T: WeakTypeTag]{
  
  val mClassType = implicitly[WeakTypeTag[T]].tpe
  val mConstructors = mClassType.members.filter(_.isMethod).map(_.asMethod).filter(_.isConstructor)
  val mConstructorsParams = mConstructors.map(_.paramss.flatten.map(_.typeSignature))

  def of[A: WeakTypeTag](a: A): Boolean = {

    val tA = implicitly[WeakTypeTag[A]].tpe

    mConstructorsParams.exists{tParams =>
      tParams.size == 1 && tA <:< tParams(0)
    }
  }

  def of[A: WeakTypeTag, B: WeakTypeTag](a: A, b: B): Boolean = {

    val tA = implicitly[WeakTypeTag[A]].tpe
    val tB = implicitly[WeakTypeTag[B]].tpe

    mConstructorsParams.exists{tParams =>
      tParams.size == 2 && tA <:< tParams(0) && tA <:< tParams(0) && tB <:< tParams(1)
    }
  }
}

def hasCtor[T: WeakTypeTag]() = new TypeCheck[T]

class Hoge(i: Int, j: String){ def this(j: String) = this(10, j) }
class Fuga(i: String, j: AnyRef){ def this(j: AnyRef) = this("fuga", j) }

relp.scala

scala> hasCtor[Hoge] of (10, "")
res22: Boolean = true

scala> hasCtor[Hoge] of (10, 10)
res23: Boolean = false

scala> hasCtor[Hoge] of (10)
res24: Boolean = false

scala> hasCtor[Hoge] of ("hoge")
res25: Boolean = true

scala> hasCtor[Fuga] of ("fuga", 10)
res26: Boolean = false

scala> hasCtor[Fuga] of ("fuga", "fuga")
res27: Boolean = true

scala> hasCtor[Fuga] of (10)
res28: Boolean = false

scala> hasCtor[Fuga] of (new AnyRef)
res29: Boolean = true