3.11.1 breaks argument matching in Ruby 2.7

[drcapulet]

Subject of the issue

When delegating using **kwargs, the spec fails when passed no keyword arguments in 2.7 (no issues with 3.0).

Your environment

• Ruby version: 2.7
• rspec-mocks version: 3.11.1

Steps to reproduce

# frozen_string_literal: true

begin
  require "bundler/inline"
rescue LoadError => e
  $stderr.puts "Bundler version 1.10 or later is required. Please update your Bundler"
  raise e
end

gemfile(true) do
  source "https://rubygems.org"

  gem "rspec", "3.11.0"
  gem "rspec-mocks", "3.11.1"
end

puts "Ruby version is: #{RUBY_VERSION}"
require 'rspec/autorun'

def call(client, name, *args, **kwargs)
  client.public_send(name, *args, **kwargs)
end

RSpec.describe 'args broken' do
  let(:client) { double('@client') }

  it 'works' do
    expect(client).to receive(:foo).with('a', 1)

    call(client, :foo, 'a', 1)
  end

  it 'works with keyword args' do
    expect(client).to receive(:foo).with('a', 1, baz: 5)

    call(client, :foo, 'a', 1, baz: 5)
  end
end

Expected behavior

Fetching gem metadata from https://rubygems.org/..
Resolving dependencies...
Using bundler 2.3.4
Using rspec-support 3.11.0
Using diff-lcs 1.5.0
Using rspec-core 3.11.0
Using rspec-expectations 3.11.0
Using rspec-mocks 3.11.0
Using rspec 3.11.0
Ruby version is: 2.7.5
..

Finished in 0.00934 seconds (files took 0.06848 seconds to load)
2 examples, 0 failures

Actual behavior

Fetching gem metadata from https://rubygems.org/..
Resolving dependencies...
Using bundler 2.3.4
Using diff-lcs 1.5.0
Using rspec-support 3.11.0
Using rspec-expectations 3.11.0
Using rspec-core 3.11.0
Using rspec-mocks 3.11.1
Using rspec 3.11.0
Ruby version is: 2.7.5
F.

Failures:

  1) args broken works
     Failure/Error: client.public_send(name, *args, **kwargs)
       #<Double "@client"> received unexpected message :foo with ("a", 1)
     # new.rb:21:in `public_send'
     # new.rb:21:in `call'
     # new.rb:30:in `block (2 levels) in <main>'

Finished in 0.00692 seconds (files took 0.07046 seconds to load)
2 examples, 1 failure

Failed examples:

rspec new.rb:27 # args broken works