[ruby-core:113363] [Ruby master Feature#19620] allow non-module rescue filters that implement the === opertor

27 Apr 2023

      Issue #19620 has been reported by bughit (bug hit).

----------------------------------------
Feature #19620: allow non-module rescue filters that implement the === opertor
https://bugs.ruby-lang.org/issues/19620

* Author: bughit (bug hit)
* Status: Open
* Priority: Normal
----------------------------------------
```ruby
module FooErrorFilter
  def self.===(e)
    e.message =~ /foo/
  end
end

def foo_error_filter
  FooErrorFilter
end

begin
  raise 'foo error'
rescue foo_error_filter => e
  p e.message
end
```

Filter matching is done via the `===` operator, which is why the rescue filter modules don't need to be exception classes. But they are required to be modules, why? Since the rescue filter object is only used for the `===` operator it should accept any object supporting it. The module restriction seems arbitrary and pointless.

```ruby
begin
  raise 'foo error'
rescue ->e{e.message =~ /foo/}
  p e.message
end
```

-- 
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