[ruby-core:121107] [Ruby master Bug#20968] `Array#fetch_values` unexpected method name in stack trace

Issue #20968 has been updated by mame (Yusuke Endoh).


This issue was discussed briefly at the dev meeting and Matz agreed with koic's expectation.

https://github.com/ruby/dev-meeting-log/blob/47882270bd90fb0027e8fe62e421b398d6b3195b/2025/DevMeeting-2025-01-09.md?plain=1#L454

---

The following is my opinion.

I agree that this is not a bug, but I think koic's expectations are clearly better than the current from a user benefit perspective, not from a consistency perspective.
I think it is significantly unlikely that `<internal:array>:211` is valuable information for user to debug a bug.
It would be more convenient to combine `<internal>` backtraces into one and substitute the name of the calling Ruby source file and line number, as in the current C-implemented method.

----------------------------------------
Bug #20968: `Array#fetch_values` unexpected method name in stack trace
https://bugs.ruby-lang.org/issues/20968#change-112027

* Author: koic (Koichi ITO)
* Status: Open
* ruby -v: ruby 3.4.0dev (2024-12-19T04:44:56Z master 2783868de2) +PRISM [x86_64-darwin23]
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------

It seems that the current Ruby implementation is displaying unexpected method name in stack trace.

## Expected

Similar to `Hash#fetch_values`, the method name `Array#fetch_values` is expected to be displayed in the stack trace.

```console
$ ruby -e '{k: 42}.fetch_values(:unknown)'
-e:1:in 'Hash#fetch_values': key not found: :unknown (KeyError)
        from -e:1:in '<main>'

$ ruby -e '[1].fetch_values(42)'
-e:1:in 'Array#fetch_values': index 42 outside of array bounds: -1...1 (IndexError)
        from -e:1:in '<main>'
```


## Actual

The stack trace displays the `Array#fetch` method, which user is not aware of, along with the `<internal.array>` stack trace.

```console
$ ruby -e '[1].fetch_values(42)'
<internal:array>:211:in 'Array#fetch': index 42 outside of array bounds: -1...1 (IndexError)
        from <internal:array>:211:in 'block in Array#fetch_values'
        from <internal:array>:211:in 'Array#map!'
        from <internal:array>:211:in 'Array#fetch_values'
        from -e:1:in '<main>'
```


It likely requires an approach such as implementing it in C, as suggested in https://github.com/ruby/ruby/pull/11555.



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