2.12.x regression: spire no longer compiles after scala/scala#9356

[SethTisue]

@retronym after scala/scala#9356, spire no longer compiles; ++2.12.14-bin-f854b0f ; coreJVM/compile:

[error] scala.reflect.internal.Types$TypeError: type mismatch;
[error]  found   : Double
[error]  required: Object

this came up over at scala/community-build#1349

[retronym]

I'm taking a look now, thanks for bisecting this.

[retronym]

Minimized:

import scala.reflect.ClassTag

object Test {
  def main(args: Array[String]): Unit = {
    apply[String]("")
    apply[Double](1d)
  }

  def apply[@specialized(Double) C: ClassTag](c: C): Unit = {
    println(Array(c).getClass)
  }
}

[SethTisue]

green in community build