Issue #15027 has been updated by mame (Yusuke Endoh).

Assignee set to matz (Yukihiro Matsumoto)
Status changed from Feedback to Assigned

Matz, do you accept the suggested patch?

To be honest, I'm negative against this patch.  It brings false consistency.  The current behavior is very easy to explain; `Struct#select` is just overridden.  A redefinition check is a magic.

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Bug #15027: When Struct#each method is overriden Struct#select and Struct#to_a use wrong collections
https://bugs.ruby-lang.org/issues/15027#change-83028

* Author: bruno (Bruno Sutic)
* Status: Assigned
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
* Target version: 
* ruby -v: 2.6.0dev
* Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN
----------------------------------------
### Bug

Here's the code snippet that should reproduce the problem:

~~~ ruby
class Foo < Struct.new(:bar)
  def each(&block)
    [:baz, :qux].each(&block)
  end
end

foo = Foo.new(:foo)
foo.map(&:itself) # => [:baz, :qux]  # OK

foo.to_a # => [:foo]  # NOT OK, expected [:baz, :qux]
foo.select(&:itself) # => [:foo]  # NOT OK, expected [:baz, :qux]
~~~

As you can see, even tho we defined another collection for use by overriding `#each`, the `to_a` and `select` still use `Struct`'s original collection.

The problem seem to be with `Struct#to_a` and `Struct#select` methods from `struct.c` file that are defined unnecessarily.

### Proposed solution

The attached solution simply deletes `Struct#select` and `Struct#to_a`. A couple tests are added to show everything still works as before.

Please let me know if I can provide any more info and I'll be ready to do so.

---Files--------------------------------
struct_enumerable_fix.patch (2.8 KB)
struct_enumerable_fix2.patch (1.51 KB)


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