[ruby-core:108294] [Ruby master Bug#18743] Enumerator#next / peek re-use each others stacktraces

[sos4nt <noreply@ruby-lang.org>]

Issue #18743 has been reported by sos4nt (Stefan Schüßler).

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Bug #18743: Enumerator#next / peek re-use each others stacktraces
https://bugs.ruby-lang.org/issues/18743

* Author: sos4nt (Stefan Schüßler)
* Status: Open
* Priority: Normal
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
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I encountered an odd behavior.

If I rescue the `StopIteration` exception from `peek` and call `next` afterwards: (or vice-versa)

```ruby
# enum.rb             # 1
                      # 2
enum = [].each        # 3
enum.peek rescue nil  # 4
enum.next             # 5
```

it will show the stacktrace from the rescued `peek` call:

```
$ ruby enum.rb
enum.rb:4:in `peek': iteration reached an end (StopIteration)
	from enum.rb:4:in `<main>'
```

Whereas the error should refer to `next` on line number 5.

The same happens when calling `peek` after `next` or when having muliple `peek` / `next` calls:

```ruby
# enum.rb                # 1
                         # 2
enum = [].each           # 3
enum.peek rescue nil     # 4
enum.next rescue nil     # 5
enum.peek rescue nil     # 6
puts "line #{__LINE__}"  # 7
enum.next                # 8
```

The stacktrace from the first (rescued) `peek` or `next` call will be shown which doesn't reflect the actual error location:

```
$ ruby enum.rb
line 7
enum.rb:4:in `peek': iteration reached an end (StopIteration)
	from enum.rb:4:in `<main>'
```

This is very confusing when debugging code.



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