From: "Eregon (Benoit Daloze) via ruby-core" <ruby-core@...>
Date: 2023-01-04T17:09:46+00:00
Subject: [ruby-core:111629] [Ruby master Feature#8088] Method#parameters (and friends) should provide useful information about core methods

Issue #8088 has been updated by Eregon (Benoit Daloze).


One way nowadays to do this is to use the `Primitive.foo` system and define the method in Ruby code.

Another would be to add a new `rb_define_method` variant to which the parameters can be passed.
That could then be used for all core methods.
As a note, `rb_define_method` does give `parameters` if the passed arity is >= 0 (e.g., `Process.method(:gid=).parameters # => [[:req]]`), but not if the passed arity is -1, which is this issue.

Having parameter names is valuable notably for `Method#inspect` e.g.:
```
> "".method(:gsub)
CRuby:
=> #<Method: String#gsub(*)>
TruffleRuby:
=> #<Method: String#gsub(pattern, replacement=..., &block) <internal:core> core/string.rb:844>
```

----------------------------------------
Feature #8088: Method#parameters (and friends) should provide useful information about core methods
https://bugs.ruby-lang.org/issues/8088#change-101001

* Author: headius (Charles Nutter)
* Status: Open
* Priority: Normal
----------------------------------------
I was wiring up #parameters to work for native methods today when I realized MRI doesn't give very good information about variable-arity native methods:

```
$ ruby2.0.0 -e "p ''.method(:gsub).to_proc.parameters"
[[:rest]]

$ jruby -e "p ''.method(:gsub).to_proc.parameters"
[[:req], [:opt]]
```

I think MRI should present the same as JRuby here; gsub is obviously not a rest-arg method and you can't call it with less than 1 or more than 2 arguments. JRuby's presenting the right output here.

I'm probably going to have to change JRuby to do the less-helpful version so we're compliant and tests pass, but I think the specification of #parameters should be that it presents the JRuby version about rather than the MRI version.



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