Add test case

Author: liufengyun

tests/init/pos/patternMatcher.scala

@@ -0,0 +1,8 @@
+import scala.collection.mutable
+
+class Translater:
+  val count = new mutable.HashMap[Int, Int] {
+    override def default(key: Int) = 0
+  }
+  count.get(10)
+  val n = 10