} else {
JSType found = instance.getPropertyType(prop);
JSType required
= implementedInterface.getImplicitPrototype().getPropertyType(prop);
found = found.restrictByNotNullOrUndefined();
required = required.restrictByNotNullOrUndefined();
if (!found.canAssignTo(required)) {
// Implemented, but not correctly typed
FunctionType constructor
= implementedInterface.toObjectType().getConstructor();
registerMismatch(found, required, report(t.makeError(n,