From: mame@...
Date: 2021-04-16T06:21:06+00:00
Subject: [ruby-core:103473] [Ruby master Feature#17749] Const source	location without name

Issue #17749 has been updated by mame (Yusuke Endoh).


@tenderlove I'm not sure about the use case. What purpose do you want this for? Memory profiling?

`const_source_location` and `source_location` are very similar but different for an anonymou class. The former returns the site where the class object is assigned to a constant, while the latter returns the site where it is created. But in almost all cases, they are same and redundant. I don't think it is a good idea to introduce similar and redundant fields in terms of maintenance, unless it is really needed. So, I'd like to ask a question: is the difference really needed for your use case?

(I'm never negative for this proposal, but I wanted to confirm.)

----------------------------------------
Feature #17749: Const source location without name
https://bugs.ruby-lang.org/issues/17749#change-91571

* Author: tenderlovemaking (Aaron Patterson)
* Status: Open
* Priority: Normal
----------------------------------------
Hi,

I would like to be able to ask a class or module what its source location is without knowing the name.  For example, I want to do this:

```ruby
module A
  class B
  end
end

p A::B.const_source_location
```

In other works `A::B.const_source_location` would be equivalent to `A.const_source_location(:B)`.

The reason I want to do this is because sometimes it is very difficult to get the name of a constant, and sometimes I don't have access to the constant that "encloses" the class or module.

One example:

```ruby
ObjectSpace.each_object(Class) do |k|
  p k.const_source_location
end
```

In this case I have class objects, but I can't tell what constant `k` was defined *inside* of.  Also I can't trust the "name" method on `k` because sometimes it's not the default method (of course I could work around that, but it's not fun).

I've attached a patch that implements the feature, and there is a PR [here](https://github.com/ruby/ruby/pull/4324)

Side note: I think I would like "source_location" better than `const_source_location`, but I wanted to just file a feature request so we could talk about the feature in general.

---Files--------------------------------
0001-Add-constant-location-information-to-classes.patch (5.34 KB)
0001-Add-constant-location-information-to-classes.patch (5.97 KB)


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