for a in b; end

Before:
  // access flags 1
  public block_0$RUBY$__for__(Lorg/jruby/runtime/ThreadContext;Lorg/jruby/runtime/builtin/IRubyObject;Lorg/jruby/runtime/builtin/IRubyObject;)Lorg/jruby/runtime/builtin/IRubyObject;
    TRYCATCHBLOCK L0 L1 L1 org/jruby/exceptions/JumpException$RedoJump
    ALOAD 1
    INVOKEVIRTUAL org/jruby/runtime/ThreadContext.getRuntime ()Lorg/jruby/Ruby;
    ASTORE 6
    ALOAD 6
    INVOKEVIRTUAL org/jruby/Ruby.getNil ()Lorg/jruby/runtime/builtin/IRubyObject;
    ASTORE 8
    ALOAD 1
    INVOKEVIRTUAL org/jruby/runtime/ThreadContext.getCurrentScope ()Lorg/jruby/runtime/DynamicScope;
    ASTORE 5
    ALOAD 5
    INVOKEVIRTUAL org/jruby/runtime/DynamicScope.getValues ()[Lorg/jruby/runtime/builtin/IRubyObject;
    ASTORE 7
    ALOAD 3
    ALOAD 5
    SWAP
    INVOKEVIRTUAL org/jruby/runtime/DynamicScope.setValueZeroDepthZero (Lorg/jruby/runtime/builtin/IRubyObject;)Lorg/jruby/runtime/builtin/IRubyObject;
    ALOAD 5
    SWAP
    INVOKEVIRTUAL org/jruby/runtime/DynamicScope.setValueZeroDepthZero (Lorg/jruby/runtime/builtin/IRubyObject;)Lorg/jruby/runtime/builtin/IRubyObject;
    POP
   L0
   FRAME FULL [ruby/__dash_e__ org/jruby/runtime/ThreadContext org/jruby/runtime/builtin/IRubyObject org/jruby/runtime/builtin/IRubyObject T org/jruby/runtime/DynamicScope org/jruby/Ruby [Lorg/jruby/runtime/builtin/IRubyObject; org/jruby/runtime/builtin/IRubyObject] []
    ALOAD 8
    ARETURN
   L1
   FRAME SAME1 org/jruby/exceptions/JumpException$RedoJump
    POP
    GOTO L0
    LOCALVARIABLE locals Lorg/jruby/runtime/DynamicScope; L0 L1 5
    MAXSTACK = 2
    MAXLOCALS = 9


After:
  // access flags 1
  public block_0$RUBY$__for__(Lorg/jruby/runtime/ThreadContext;Lorg/jruby/runtime/builtin/IRubyObject;Lorg/jruby/runtime/builtin/IRubyObject;)Lorg/jruby/runtime/builtin/IRubyObject;
    ALOAD 1
    INVOKEVIRTUAL org/jruby/runtime/ThreadContext.getRuntime ()Lorg/jruby/Ruby;
    ASTORE 6
    ALOAD 6
    INVOKEVIRTUAL org/jruby/Ruby.getNil ()Lorg/jruby/runtime/builtin/IRubyObject;
    ASTORE 8
    ALOAD 1
    INVOKEVIRTUAL org/jruby/runtime/ThreadContext.getCurrentScope ()Lorg/jruby/runtime/DynamicScope;
    ASTORE 5
    ALOAD 3
    DUP
    ASTORE 11
    ASTORE 11
   L0
    ALOAD 8
    ARETURN
   L1
    LOCALVARIABLE a Lorg/jruby/runtime/builtin/IRubyObject; L0 L1 11
    MAXSTACK = 2
    MAXLOCALS = 12