[ruby-core:94775] [Ruby master Feature#16137] Add === to UnboundMethod

Issue #16137 has been updated by nobu (Nobuyoshi Nakada).


As `UnboundMethod#bind_call` raises a `TypeError` unless the argument class matches, it isn't for `when`.

And the example doesn't look more readable to me.

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Feature #16137: Add === to UnboundMethod
https://bugs.ruby-lang.org/issues/16137#change-81393

* Author: okuramasafumi (Masafumi OKURA)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
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# Abstract

`UnboundMethod` class should have `=== ` so that it can be used in case statement.

# Background

`Method` class has `===` method so that we can do something like:
``` ruby
require 'prime'
case 11
when Prime.method(:prime?) then :prime
end
```

However, we cannot do something like this:
```ruby
positive = Integer.instance_method(:positive?)
case 11
when positive then :positive
end
```

# Proposal

Add `===` method to `UnboundMethod` class.

# Implementation

Minimal implementation in Ruby could be:
```ruby
class UnboundMethod
  def ===(other)
    bind(other).call
  end
end
```

# Summary

`===` for `UnboundMethod` can improve readability in case statement.



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