instanceof-option

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scala> object Blah {
     |   def thing[A](a: Option[A]): Int = a match {
     |     case Some(x) => 23
     |     case None => 42
     |   }
     | }
defined object Blah

scala> :javap Blah
  Size 952 bytes
  MD5 checksum 010c9f62601e50b75cff4036fe3d146d
  Compiled from "<console>"
public class Blah$
  SourceFile: "<console>"
  InnerClasses:
       public static #43= #40 of #42; //=class  of class $line3/$read
       public static #43= #45 of #40; //=class  of class
       public static #46= #2 of #45; //Blah$=class Blah$ of class
    Scala: length = 0x0

  minor version: 0
  major version: 50
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   #1 = Utf8               Blah$
   #2 = Class              #1             //  Blah$
   #3 = Utf8               java/lang/Object
   #4 = Class              #3             //  java/lang/Object
   #5 = Utf8               <console>
   #6 = Utf8               MODULE$
   #7 = Utf8               LBlah$;
   #8 = Utf8               <clinit>
   #9 = Utf8               ()V
  #10 = Utf8               <init>
  #11 = NameAndType        #10:#9         //  "<init>":()V
  #12 = Methodref          #2.#11         //  Blah$."<init>":()V
  #13 = Utf8               thing
  #14 = Utf8               (Lscala/Option;)I
  #15 = Utf8               scala/Some
  #16 = Class              #15            //  scala/Some
  #17 = Utf8               scala/None$
  #18 = Class              #17            //  scala/None$
  #19 = Utf8               Lscala/None$;
  #20 = NameAndType        #6:#19         //  MODULE$:Lscala/None$;
  #21 = Fieldref           #18.#20        //  scala/None$.MODULE$:Lscala/None$;
  #22 = Utf8               equals
  #23 = Utf8               (Ljava/lang/Object;)Z
  #24 = NameAndType        #22:#23        //  equals:(Ljava/lang/Object;)Z
  #25 = Methodref          #4.#24         //  java/lang/Object.equals:(Ljava/lang/Object;)Z
  #26 = Utf8               scala/MatchError
  #27 = Class              #26            //  scala/MatchError
  #28 = Utf8               (Ljava/lang/Object;)V
  #29 = NameAndType        #10:#28        //  "<init>":(Ljava/lang/Object;)V
  #30 = Methodref          #27.#29        //  scala/MatchError."<init>":(Ljava/lang/Object;)V
  #31 = Utf8               this
  #32 = Utf8               a
  #33 = Utf8               Lscala/Option;
  #34 = Utf8               scala/Option
  #35 = Class              #34            //  scala/Option
  #36 = Methodref          #4.#11         //  java/lang/Object."<init>":()V
  #37 = NameAndType        #6:#7          //  MODULE$:LBlah$;
  #38 = Fieldref           #2.#37         //  Blah$.MODULE$:LBlah$;
  #39 = Utf8
  #40 = Class              #39            //
  #41 = Utf8               $line3/$read
  #42 = Class              #41            //  $line3/$read
  #43 = Utf8
  #44 = Utf8
  #45 = Class              #44            //
  #46 = Utf8               Blah$
  #47 = Utf8               Code
  #48 = Utf8               LocalVariableTable
  #49 = Utf8               LineNumberTable
  #50 = Utf8               StackMapTable
  #51 = Utf8               Signature
  #52 = Utf8               <A:Ljava/lang/Object;>(Lscala/Option<TA;>;)I
  #53 = Utf8               SourceFile
  #54 = Utf8               InnerClasses
  #55 = Utf8               Scala
{
  public static final Blah$ MODULE$;
    flags: ACC_PUBLIC, ACC_STATIC, ACC_FINAL

  public static {};
    flags: ACC_PUBLIC, ACC_STATIC
    Code:
      stack=1, locals=0, args_size=0
         0: new           #2                  // class Blah$
         3: invokespecial #12                 // Method "<init>":()V
         6: return

  public <A extends java/lang/Object> int thing(scala.Option<A>);
    flags: ACC_PUBLIC
    Code:
      stack=3, locals=4, args_size=2
         0: aload_1
         1: astore_2
         2: aload_2
         3: instanceof    #16                 // class scala/Some
         6: ifeq          15
         9: bipush        23
        11: istore_3
        12: goto          28
        15: getstatic     #21                 // Field scala/None$.MODULE$:Lscala/None$;
        18: aload_2
        19: invokevirtual #25                 // Method java/lang/Object.equals:(Ljava/lang/Object;)Z
        22: ifeq          30
        25: bipush        42
        27: istore_3
        28: iload_3
        29: ireturn
        30: new           #27                 // class scala/MatchError
        33: dup
        34: aload_2
        35: invokespecial #30                 // Method scala/MatchError."<init>":(Ljava/lang/Object;)V
        38: athrow
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
               0      39     0  this   LBlah$;
               0      39     1     a   Lscala/Option;
      LineNumberTable:
        line 8: 0
        line 9: 2
        line 10: 15
        line 8: 28
      StackMapTable: number_of_entries = 3
           frame_type = 252 /* append */
             offset_delta = 15
        locals = [ class scala/Option ]
           frame_type = 252 /* append */
             offset_delta = 12
        locals = [ int ]
           frame_type = 250 /* chop */
          offset_delta = 1

    Signature: #52                          // <A:Ljava/lang/Object;>(Lscala/Option<TA;>;)I

  public Blah$();
    flags: ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: invokespecial #36                 // Method java/lang/Object."<init>":()V
         4: aload_0
         5: putstatic     #38                 // Field MODULE$:LBlah$;
         8: return
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
               0       9     0  this   LBlah$;
      LineNumberTable:
        line 16: 0
}

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