> %w[a b c].tap { |s| print(s) }.join &:+ #=> "abc" -> abc
> to_s #=> "main"
> tap { |o| o.to_s } #=> main (toplevel object)
> yield_self { |s| s.to_s } #=> "main" (block yielding result)

[38] pry(main)> st = Struct.new(:foo, :bar)
=> #<Class:0x000055dca2b6c630>
[39] pry(main)> st.ancestors
=> [#<Class:0x000055dca2b6c630>, Struct, Enumerable, Object, PP::ObjectMixin, Kernel, BasicObject]

[42] pry(main)> st.superclass
=> Struct

通过在字节码中移除了全部 trace 指令提升了大约 5-10% 的性能。trace 指令的引入是为了提供 TracePoint 的支持。然而，在大多数情况，TracePoint 不会被用到，trace 指令增加了额外的开销。作为替代，我们实现了一个动态指令技术，详情见 [功能 #14104]。

dse@susepc:~$ pry
[1] pry(main)> Class::Struct
NameError: uninitialized constant Class::Struct
Did you mean?  Struct
from (pry):1:in `__pry__'

dse@susepc:~$ ruby2.3
require 'irb'
IRB.start
irb(main):001:0> Class::Struct
(irb):1: warning: toplevel constant Struct referenced by Class::Struct
=> Struct

dse@susepc:~$ pry
[1] pry(main)> Object::Class
=> Class
[2] pry(main)> Class.ancestors
=> [Class, Module, Object, PP::ObjectMixin, Kernel, BasicObject]