[ruby-core:98409] [Ruby master Bug#16852] Refining Enumerable fails with ruby 2.7

Issue #16852 has been updated by osyo (manga osyo).


hi.
Thanks for issues :)

I got the same error when `include M` after `refine M`.

```ruby
module M; end
class X
  include M
end

module RefinementBug
  refine M do
    def refined_method
      puts "Called #refined_method"
    end
  end
end

class Y
  # Error if include M
  include M
end

using RefinementBug

puts "Using Ruby #{RUBY_VERSION}"

# error: undefined method `refined_method' for #<X:0x000055d4e22468c0> (NoMethodError)
X.new.refined_method
```

see: https://wandbox.org/permlink/bE3AvLBRnu07wtJY


By the way, RSpec caused an error due to `require "stringio"`.
This is because `stringio` does `include Enumerable`.

```ruby
module RefinementBug
  refine Enumerable do
    def refined_method
      puts "Called #refined_method"
    end
  end
end

# Error if `require "stringio"`
require "stringio"

using RefinementBug

puts "Using Ruby #{RUBY_VERSION}"

# error: undefined method `refined_method' for []:Array (NoMethodError)
[].refined_method
```


----------------------------------------
Bug #16852: Refining Enumerable fails with ruby 2.7
https://bugs.ruby-lang.org/issues/16852#change-85679

* Author: parker (Parker Finch)
* Status: Open
* Priority: Normal
* ruby -v: ruby 2.7.1p83 (2020-03-31 revision a0c7c23c9c) [x86_64-darwin19]
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
When using [rspec](https://github.com/rspec/rspec-core) and ruby 2.7 I am unable to refine `Enumerable`. I have created an [issue in rspec](https://github.com/rspec/rspec-core/issues/2727) but I'm wondering if there's an underlying ruby issue. (This bug does not occur when using ruby 2.6 or 2.5.)

### Code to reproduce
(Also attached as a `.tar.gz`):
```ruby
# file: refinement_bug.rb
module RefinementBug
  refine Enumerable do
    def refined_method
      puts "Called #refined_method"
    end
  end
end
```
```ruby
# file: spec/spec_helper.rb
require_relative "../refinement_bug"
```
```ruby
# file: spec/test.rb

require_relative "../refinement_bug"

using RefinementBug

puts "Using Ruby #{RUBY_VERSION}"
[].refined_method
```
After installing rspec (`gem install rspec`), call via `rspec spec/test.rb --format progress --require spec_helper`.

### Expected Behavior
When run on Ruby 2.6 and 2.5 I get the expected behavior. The `Enumerable` module is refined, which allows an instance of `Array` to call `#refined_method`.
```
# This is output when running on ruby 2.6.6, and is expected.
~/minimal_refinement_failure> rspec spec/test.rb
Using Ruby 2.6.6
Called #refined_method
No examples found.

Finished in 0.0004 seconds (files took 0.08706 seconds to load)
0 examples, 0 failures
```

### Actual Behavior
When I run the same code on ruby 2.7 I get a `NoMethodError`, suggesting that the `Enumerable` module has not been refined.
```
~/minimal_refinement_failure> rspec spec/test.rb
Using Ruby 2.7.1

An error occurred while loading ./spec/test.rb.
Failure/Error: [].refined_method

NoMethodError:
  undefined method `refined_method' for []:Array
# ./spec/test.rb:8:in `<top (required)>'
No examples found.

Finished in 0.00003 seconds (files took 0.12287 seconds to load)
0 examples, 0 failures, 1 error occurred outside of examples
```

### Investigation
There are a few changes that prevent this bug from manifesting:
* If I refine `Kernel` instead of `Enumerable` then I get the expected behavior using Ruby 2.7.
* If I refine `Array` instead of `Enumerable` then I get the expected behavior using Ruby 2.7.

This bug does *not* manifest if run directly via ruby (i.e. `ruby -r ./spec/spec_helper.rb spec/test.rb` succeeds). It only manifests when run via `rspec`.

I can also get the expected behavior by changing the rspec options:
* If I don't use the `--require` option with `rspec` (e.g. run it as `rspec spec/test.rb --format progress`) then I get the expected behavior.
* If I don't use the `--format` option with `rspec` (e.g. run it as `rspec spec/test.rb --require spec_helper`) then I get the expected behavior.

This suggests the underlying issue might be in `rspec`. But if it is, I'm curious why the change to ruby 2.7 causes this to manifest, and whether Ruby 2.7 accidentally broke some expected behavior.

Thank you for looking into this, I am very confused :)
Let me know how I can help with this!

---Files--------------------------------
minimal_refinement_failure.tar.gz (415 Bytes)


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