Merge pull request jruby#9192 from enebo/topic/kwarg_fix

Stab at Fixing jruby#8976

Author: headius

core/src/main/java/org/jruby/ir/runtime/IRRuntimeHelpers.java

@@ -717,7 +717,13 @@ private static IRubyObject receiveSpecificArityHashKeywords(ThreadContext contex
         int callInfo = ThreadContext.resetCallInfo(context);
         boolean isKwarg = (callInfo & CALL_KEYWORD) != 0;
 
-        return receiverSpecificArityKwargsCommon(context, last, isKwarg);
+        if ((callInfo & CALL_SPLATS) != 0 && last.isRuby2KeywordHash()) {
+            return last.dupFast(context);
+        }
+
+        return isKwarg ?
+                last.dupFast(context) :
+                last;
     }
 
     private static IRubyObject receiveSpecificArityRuby2HashKeywords(ThreadContext context, RubyHash last) {
@@ -735,13 +741,7 @@ private static IRubyObject receiveSpecificArityRuby2HashKeywords(ThreadContext c
             return hash;
         }
 
-        return receiverSpecificArityKwargsCommon(context, last, false);
-    }
-
-    private static IRubyObject receiverSpecificArityKwargsCommon(ThreadContext context, RubyHash last, boolean isKwarg) {
-        return isKwarg || last.isRuby2KeywordHash() ?
-                last.dupFast(context) :
-                last;
+        return last;
     }
 
     /**

spec/ruby/language/keyword_arguments_spec.rb

@@ -86,6 +86,20 @@ def m(*a)
     m(*[], 42, **{}).should == [42]
   end
 
+  context "marked as ruby2_keywords_hash" do
+    it "is not copied when passed as a positional argument" do
+      h = Hash.ruby2_keywords_hash(a:1)
+
+      def bar(a)
+        a
+      end
+
+      h2 = bar(h)
+      h2.should equal(h)
+      Hash.ruby2_keywords_hash?(h).should == true
+    end
+  end
+
   context "**" do
     it "copies a non-empty Hash for a method taking (*args)" do
       def m(*args)