Following Scala mailing lists, different people often say: "compiler rewrites this [scala] code into this [java/scala??] code". For example, from one of the latest threads, if Scala sees
class C(i: Int = 4) { ... }
then the compiler rewrites this as (effectively):
class C(i: Int) { ... }
object C {
def init$default$1: Int = 4
}
How can I find out, what will be the compiler output for my code? Should I decompile the resulting bytecode for that?
You can use "-print" as compiler option, and scalac will remove all Scala-specific features.
For example, here is the original code:
class Main
{
def test (x: Any) = x match {
case "Hello" => println ("Hello World")
case e: String => println ("String")
case i: Int => println ("Int")
case _ => println ("Something else")
}
}
And if you use "scalac -print" to compile it, you will get the following Scala code.
[[syntax trees at end of cleanup]]// Scala source: Test.scala
package <empty> {
class Main extends java.lang.Object with ScalaObject {
def test(x: java.lang.Object): Unit = {
<synthetic> val temp1: java.lang.Object = x;
if (temp1.==("Hello"))
{
scala.this.Predef.println("Hello World")
}
else
if (temp1.$isInstanceOf[java.lang.String]())
{
scala.this.Predef.println("String")
}
else
if (temp1.$isInstanceOf[Int]())
{
scala.this.Predef.println("Int")
}
else
{
scala.this.Predef.println("Something else")
}
};
def this(): Main = {
Main.super.this();
()
}
}
}
One can look at the generated bytecode with
javap -c -private ClassNameWithoutDotClass
