From: nobu@...
Date: 2021-07-15T14:35:47+00:00
Subject: [ruby-core:104620] [Ruby master Bug#18011] `Method#parameters` is incorrect for forwarded arguments

Issue #18011 has been updated by nobu (Nobuyoshi Nakada).


Changing `parameters` broke rbs test.

https://github.com/nobu/ruby/runs/3076547487?check_suite_focus=true#step:15:350
```
Failure: test_argument_forwarding(RBS::RuntimePrototypeTest)
/home/runner/work/ruby/ruby/src/gems/src/rbs/test/test_helper.rb:194:in `assert_write'
/home/runner/work/ruby/ruby/src/gems/src/rbs/test/rbs/runtime_prototype_test.rb:231:in `block (2 levels) in test_argument_forwarding'
     228:         manager.build do |env|
     229:           p = Runtime.new(patterns: ["RBS::RuntimePrototypeTest::TestForArgumentForwarding"], env: env, merge: true)
     230: 
  => 231:           assert_write p.decls, <<-EOF
     232: class RBS::RuntimePrototypeTest::TestForArgumentForwarding
     233:   public
     234: 
/home/runner/work/ruby/ruby/src/gems/src/rbs/test/test_helper.rb:158:in `block in build'
/home/runner/work/ruby/ruby/src/lib/tmpdir.rb:96:in `mktmpdir'
/home/runner/work/ruby/ruby/src/gems/src/rbs/test/test_helper.rb:139:in `build'
/home/runner/work/ruby/ruby/src/gems/src/rbs/test/rbs/runtime_prototype_test.rb:228:in `block in test_argument_forwarding'
/home/runner/work/ruby/ruby/src/gems/src/rbs/test/test_helper.rb:73:in `new'
/home/runner/work/ruby/ruby/src/gems/src/rbs/test/rbs/runtime_prototype_test.rb:227:in `test_argument_forwarding'
<"class RBS::RuntimePrototypeTest::TestForArgumentForwarding\n" +
"  public\n" +
"\n" +
"  def foo: (*untyped) { (*untyped) -> untyped } -> untyped\n" +
"end\n"> expected but was
<"class RBS::RuntimePrototypeTest::TestForArgumentForwarding\n" +
"  public\n" +
"\n" +
"  def foo: (*untyped, **untyped) { (*untyped) -> untyped } -> untyped\n" +
"end\n">

diff:
  class RBS::RuntimePrototypeTest::TestForArgumentForwarding
    public
  
?   def foo:                         (*untyped) { (*untyped)  -> untyped } -> untyped
?            (*untyped, **untyped) {            ->          }                        
?           ++++++++++++++++++++++++            ????        ?           -------------
  end
```

`Method#ruby2_keywords?` may be needed, I guess.

----------------------------------------
Bug #18011: `Method#parameters` is incorrect for forwarded arguments
https://bugs.ruby-lang.org/issues/18011#change-92912

* Author: josh.cheek (Josh Cheek)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.0.1p64 (2021-04-05 revision 0fb782ee38) [arm64-darwin20]
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN
----------------------------------------
When asking a method about its parameters, forwarded arguments say they are a rest and a block (`wrapper1` in the example below).
However, when we use that signature, it raises an ArgumentError (`wrapper2` in the example below).
When I add a keyrest to the signature, it works as expected (`wrapper3` in the example below).
So I think forwarded arguments should include a keyrest in the output of `Method#parameters`

```ruby
def wrapped(ord, kw:) = [ord, {kw: kw}]

methods = [
 def wrapper1(...)         = wrapped(...),
 def wrapper2(*r, &b)      = wrapped(*r, &b),
 def wrapper3(*r, **k, &b) = wrapped(*r, **k, &b),
]

methods.each do |name|
  puts File.read(__FILE__)[/#{name}\(.*?\)/]
  puts "  params: #{method(name).parameters.inspect}"
  puts "  result: #{(method(name).call 123, kw: 456 rescue $!).inspect}"
  puts
end
```

Output:

```
wrapper1(...)
  params: [[:rest, :*], [:block, :&]]
  result: [123, {:kw=>456}]

wrapper2(*r, &b)
  params: [[:rest, :r], [:block, :b]]
  result: #<ArgumentError: wrong number of arguments (given 2, expected 1; required keyword: kw)>

wrapper3(*r, **k, &b)
  params: [[:rest, :r], [:keyrest, :k], [:block, :b]]
  result: [123, {:kw=>456}]
```



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