[ruby-core:119101] [Ruby master Bug#20716] Different instance_method behavior in Ruby 2.7 and Ruby 3.x

9 Sep 2024

      Issue #20716 has been updated by natton (Tien Truong).

Hi Evans,

Thank you for your confirmation.
I am new here so is there anything I can do to escalate this or how can I help to resolve this issue?

----------------------------------------
Bug #20716: Different instance_method behavior in Ruby 2.7 and Ruby 3.x
https://bugs.ruby-lang.org/issues/20716#change-109689

* Author: natton (Tien Truong)
* Status: Open
* ruby -v: 3.3.1
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
Hi, I am working on upgrading our project from 2.7 to 3.x and found a breaking change in `instance_method` behavior.
Here is the code snippet
```
module A
  def test(*args)
    super
  end
end

module B
  def test(a)
    puts a
  end
end

B.prepend(A)

a = lambda do
  puts 'lambda'
end

class C
  include B
end

B.instance_method(:test).bind(C.new).call(1)
# Ruby 2.7: 1
# Ruby 3.0: 1
# Ruby 3.1: 1

B.module_exec do
  define_method(:test, a)
end

B.instance_method(:test).bind(C.new).call
# Ruby 2.7: lambda
# Ruby 3.0: wrong number of arguments (given 0, expected 1) (ArgumentError)
# Ruby 3.1: wrong number of arguments (given 0, expected 1) (ArgumentError)
```
I don't know if this is a bug or a correct intention.

My specs:
- Ruby manager: rbenv
- Tested on 
    - ruby 2.7.4p191 (2021-07-07 revision a21a3b7d23) [x86_64-linux]
    - ruby 3.0.7p220 (2024-04-23 revision 724a071175) [x86_64-linux]
    - ruby 3.1.4p223 (2023-03-30 revision 957bb7cb81) [x86_64-linux]
    - ruby 3.2.3 (2024-01-18 revision 52bb2ac0a6) [x86_64-linux]
    - ruby 3.3.1 (2024-04-23 revision c56cd86388) [x86_64-linux]

-- 
https://bugs.ruby-lang.org/