Both of these below appear to be declarations of parameterless methods named x that return an Int of 5. Why can the first not be invoked with empty parens, while the other can?
scala> def x = 5
x: Int
scala> x
res1: Int = 5
scala> x()
<console>:9: error: Int does not take parameters
x()
^
scala> def x() = 5
x: ()Int
scala> x()
res3: Int = 5
scala> x
res4: Int = 5
