Do not autosplat array in block call just because keywords accepted

If the block only accepts a single positional argument plus keywords,
then do not autosplat.  Still autosplat if the block accepts more
than one positional argument in addition to keywords.

Autosplatting a single positional argument plus keywords made sense
in Ruby 2, since a final positional hash could be used as keywords,
but it does not make sense in Ruby 3.

Fixes [Bug #18633]

1 files changed, 11 insertions, 2 deletions

diff --git a/spec/ruby/language/block_spec.rb b/spec/ruby/language/block_spec.rb
index b2a3cc84c4..f213d68ba1 100644
--- a/spec/ruby/language/block_spec.rb
+++ b/spec/ruby/language/block_spec.rb
@@ -40,8 +40,17 @@ describe "A block yielded a single" do
       m([1, 2]) { |a=5, b, c, d| [a, b, c, d] }.should == [5, 1, 2, nil]
     end
 
-    it "assigns elements to required arguments when a keyword rest argument is present" do
-      m([1, 2]) { |a, **k| [a, k] }.should == [1, {}]
+    ruby_version_is "3.2" do
+      it "does not autosplat single argument to required arguments when a keyword rest argument is present" do
+        m([1, 2]) { |a, **k| [a, k] }.should == [[1, 2], {}]
+      end
+    end
+
+    ruby_version_is ''..."3.2" do
+      # https://bugs.ruby-lang.org/issues/18633
+      it "autosplats single argument to required arguments when a keyword rest argument is present" do
+        m([1, 2]) { |a, **k| [a, k] }.should == [1, {}]
+      end
     end
 
     ruby_version_is ''..."3.0" do