M.kt

console.txt

$ kotlinc M.kt
$ javap -c MKt
Compiled from "M.kt"
public final class MKt {
  public static final void main(java.lang.String[]);
    Code:
       0: aload_0
       1: ldc           #9                  // String args
       3: invokestatic  #15                 // Method kotlin/jvm/internal/Intrinsics.checkParameterIsNotNull:(Ljava/lang/Object;Ljava/lang/String;)V
       6: aconst_null
       7: checkcast     #17                 // class java/lang/String
      10: astore_1
      11: aload_1
      12: dup
      13: ifnull        25
      16: invokevirtual #21                 // Method java/lang/String.length:()I
      19: invokestatic  #27                 // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
      22: goto          27
      25: pop
      26: aconst_null
      27: astore_2
      28: getstatic     #33                 // Field java/lang/System.out:Ljava/io/PrintStream;
      31: aload_2
      32: invokevirtual #39                 // Method java/io/PrintStream.println:(Ljava/lang/Object;)V
      35: return
}

M.kt

fun main(args: Array<String>) {
  val message: String? = null
  println(message?.length)
}