Context bound type parameter in def with explicit return type does not compile

[agboom]

The following code does not compile:

import scala.reflect.ClassTag
import scala.util._

object Main {
  class A

  def constructAs[T <: A: ClassTag]: Try[T] = Try {
    new A()
  }.flatMap {
    case inst: T => Success(inst)
    case _ =>
      val tag = implicitly[ClassTag[T]]
      Failure(new ClassCastException(s"Failed to construct instance of class ${tag.runtimeClass.getName}"))
  }
}

Dotc gives the following error:

Main.scala:10: error: type mismatch:
 found   : Main.A(inst)
 required: Nothing'
    case inst: T => Success(inst)
                            ^
one error found

If I leave out the context bound, the code compiles fine. In Scala 2.11.8 it compiles too.

Weirdly enough, if I leave out the explicit return type, it also compiles fine.