Added enum checks since enums are now supported in the IDL

Source/bindings/dart/scripts/templates/methods_cpp.template

 {##############################################################################}
 {# FIXME: We should return a rejected Promise if an error occurs in this
 function when ALL methods in this overload return Promise. In order to do so,
 we must ensure either ALL or NO methods in this overload return Promise #}
 {% macro overload_resolution_method(method) %}
 {% set overloads = method.overloads %}
 {% if method.is_static %}
   {% set offset = 0 %}
 {% else %}
   {% set offset = 1 %}
@@ skipping 229 matching lines @@
 {% elif argument.is_array_or_sequence_type %}
 {{argument.local_cpp_type}} {{argument.name}};
 {{argument.dart_value_to_local_cpp_value}};
 {% else %}
   {% if argument.is_dictionary and argument.dart_value_dictionary_cpp_value %}
 Dictionary dictionary = {{argument.dart_value_dictionary_cpp_value}};
 if (exception)
     goto fail;
   {% endif %}
 {{argument.local_cpp_type}} {{argument.name}} = {{argument.dart_value_to_local_cpp_value}};
+{% if argument.enum_validation_expression %}
+if (!({{argument.enum_validation_expression}})) {
+  exception = Dart_NewStringFromCString("param {{argument.arg_index}} not valid");
+}
+{% endif %}
 {% endif %}
 {% endif %}{# argument.is_callback_interface #}
 if (exception)
     goto fail;
 {% if argument.is_dictionary and argument.is_optional and argument.dart_value_dictionary_cpp_value %}
 if (es.hadException()) {
     exception = es.toDart(args, true);
     goto fail;
 }
 {% endif %}
@@ skipping 259 matching lines @@
 
 {##############################################################################}
 {% macro generate_symbolizer_constructor(dart_class, class_name, constructor) %}
 {% for native_entry in constructor.native_entries %}
 {% set resolver_string = native_entry.resolver_string %}
 if (nf == {{dart_class}}Internal::{{static_method_name(constructor.name, constructor.overload_index)}}) {
   return reinterpret_cast<const uint8_t*>("{{resolver_string}}");
 }
 {% endfor %}
 {% endmacro %}