JsInvocation call = new JsInvocation(sourceInfo);
JsNameRef toStringRef = new JsNameRef(sourceInfo,
polymorphicNames.get(toStringMeth));
toStringRef.setQualifier(new JsThisRef(sourceInfo));
call.setQualifier(toStringRef);
JsReturn jsReturn = new JsReturn(sourceInfo, call);
JsFunction rhs = new JsFunction(sourceInfo, topScope);
JsBlock body = new JsBlock(sourceInfo);
body.getStatements().add(jsReturn);
rhs.setBody(body);