~/projects/duby ➔ bin/duby -e "def foo(a: 1); puts a; end; foo; foo(2)"
1
2

~/projects/duby ➔ bin/dubyc -e "def foo(a: 1); puts a; end; foo; foo(2)"
javap -c
~/projects/duby ➔ javap -c dash_e
Compiled from dash_e
public class dash_e extends java.lang.Object{
public static void main(java.lang.String[]);
  Code:
   0:	invokestatic	#26; //Method foo:()V
   3:	iconst_2
   4:	invokestatic	#24; //Method foo:(I)V
   7:	return

public static void foo(int);
  Code:
   0:	getstatic	#14; //Field java/lang/System.out:Ljava/io/PrintStream;
   3:	iload_0
   4:	invokevirtual	#19; //Method java/io/PrintStream.println:(I)V
   7:	return

public static void foo();
  Code:
   0:	iconst_1
   1:	invokestatic	#24; //Method foo:(I)V
   4:	return

public dash_e();
  Code:
   0:	aload_0
   1:	invokespecial	#31; //Method java/lang/Object."<init>":()V
   4:	return

}