Scala ClassTag＆classOf和type参数。 泛型的奇怪案例

Question

Here is my code straight & simple:

package scalaproj
import scala.reflect._

case class MyClass() {}

def bar[T](cls : Class[T]) = println(cls)
def foobar[T: ClassTag] = println(classTag[T])

bar(classOf[MyClass])
foobar[MyClass]

Results: class scalaproj.GetFields$MyClass$2
         scalaproj.GetFields$MyClass$2 

Now I would like to do the following without the famous error: "class type required but T found"

def foo[T] = println(classOf[T])
foo[MyClass]

foo is just a function that takes a Generic Type Parameter and does not need a value parameter. I think this is strange given the two examples that work and all the flexibility build in into the Scala language and its handeling of generics.

Update:

Just to specify further strangeness:

def foo1[T](t : T) = {}  // no compile error

def foo2[T](): List[T] = { List[T]() }  // no compile error

def foo3[T](): T = { T() }  // compile error: "not found: value T"

A good explanation is appreciated.

Answer 1

You can't, as classOf will not work with arbitrary types (and your T is an arbitrary type).

For example:

scala> classOf[Int with String]
<console>:15: error: class type required but Int with String found
       classOf[Int with String]
               ^

You can achieve the same thing with ClassTag#runtimeClass :

def foo[T: ClassTag] = println(classTag[T].runtimeClass)