Allow trailing comma in hash pattern

(cherry picked from commit d25a4f413d)

parse.y

@@ -4053,6 +4053,10 @@ p_kwargs	: p_kwarg ',' p_kwrest
 		    {
 			$$ =  new_hash_pattern_tail(p, new_unique_key_hash(p, $1, &@$), 0, &@$);
 		    }
+		| p_kwarg ','
+		    {
+			$$ =  new_hash_pattern_tail(p, new_unique_key_hash(p, $1, &@$), 0, &@$);
+		    }
 		| p_kwrest
 		    {
 			$$ =  new_hash_pattern_tail(p, new_hash(p, Qnone, &@$), $1, &@$);

test/ruby/test_pattern_matching.rb

@@ -1042,6 +1042,15 @@ END
       end
     end
 
+    assert_block do
+      case {a: 0, b: 1}
+      in {a: 1,}
+        false
+      in {a:,}
+        true
+      end
+    end
+
     assert_syntax_error(%q{
       case _
       in "a-b":