mojo/public/tools/bindings/generators/cpp_templates/enum_declaration.tmpl

enum {{enum.name}} : int32_t {
{%- for field in enum.fields %}
{%-    if field.value %}
  {{enum.name|to_all_caps}}_{{field.name}} = {{field.value|expression_to_text}},
{%-    else %}
  {{enum.name|to_all_caps}}_{{field.name}},
{%-    endif %}
{%- endfor %}
};