report polymorphism for len builtin

Author: timfel

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/BuiltinFunctions.java

@@ -185,6 +185,7 @@
 import com.oracle.truffle.api.dsl.Fallback;
 import com.oracle.truffle.api.dsl.GenerateNodeFactory;
 import com.oracle.truffle.api.dsl.ImportStatic;
+import com.oracle.truffle.api.dsl.ReportPolymorphism;
 import com.oracle.truffle.api.dsl.Specialization;
 import com.oracle.truffle.api.dsl.TypeSystemReference;
 import com.oracle.truffle.api.frame.Frame;
@@ -1203,6 +1204,7 @@ public Object iter(Object callable, Object sentinel) {
     // len(s)
     @Builtin(name = LEN, minNumOfPositionalArgs = 1)
     @GenerateNodeFactory
+    @ReportPolymorphism
     public abstract static class LenNode extends PythonUnaryBuiltinNode {
         @Specialization(limit = "getCallSiteInlineCacheMaxDepth()")
         public int len(VirtualFrame frame, Object obj,