From: "rubyFeedback (robert heiler) via ruby-core" <ruby-core@...>
Date: 2023-12-13T20:36:12+00:00
Subject: [ruby-core:115735] [Ruby master Bug#20063] Inconsistent behavior with required vs optional parameters

Issue #20063 has been updated by rubyFeedback (robert heiler).


That last example is one very complicated def - it is probably
the most complicated one I have seen so far.

In regards to jemmai's example: what would you expect to be the
correct behaviour? I have not seen methods defined with the
same arguments (such as "(_a = 1, _a = 2)"). Do such examples
come up in real code? Is that behaviour documented or specified?

I guess the example can be generalized to using the same name
in the method definition, but then I tried it myself, thinking
this is equivalent to this:

    def foobar_optional(x = 1, x = 2)
      x
    end

Then I realised it is not:

    duplicated argument name (SyntaxError)

So now I wonder about the use case and behaviour of _ variables.

Why isn't this a SyntaxError?


----------------------------------------
Bug #20063: Inconsistent behavior with required vs optional parameters
https://bugs.ruby-lang.org/issues/20063#change-105668

* Author: jemmai (Jemma Issroff)
* Status: Open
* Priority: Normal
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
Using repeated anonymous parameters, gives different behavior with the parameters in the same order based on whether they are required or optional.
 
```
def example_with_optional(_a = 1, _a = 2)
  _a
end

def example_with_required(_a, _a)
  _a
end

p example_with_optional # 2
p example_with_required(1, 2) # 1
```

It is unexpected that these two methods would return differently given the parameters are in the same order, based on whether they are optional or required.




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