Scala currying和类型推断

在以下代码段中：

object Foo {

  def foo(a:Int)(b:Int)(c:Int) : Int = a + b + c

  def main(a:Array[String]) {

    val f = foo(1)(2) _ 
    def g : Int => Int = foo(1)(2) 
    // def h = foo(1)(2) 

    println(f(3))
    println(g(3))
    // println(h(3))
  }
}

f和g工作的定义,h的定义不是：

/home/vlad/Desktop/b.scala:9: error: missing arguments for method foo in object Main;
follow this method with `_' if you want to treat it as a partially applied function
    def h = foo(1)(2)

这是非法的原因是什么？在我看来,Scala应该能够弄清楚在调用foo(1)(2)之后你会留下一个Int =>诠释.