Bounded Structured Fields errors, containing no input bytes.

:syntax means malformed wire input; :invalid_value means an invalid value supplied for serialization. :revision_type rejects a type unavailable in the explicitly selected RFC revision; :schema_type rejects a field's disallowed item, inner-list, or parameter type. :limit means a documented bound was exceeded. :invalid_schema and :invalid_limits reject invalid configuration. :invalid_message, :invalid_field, :missing_field, and :unavailable_section identify field capture failures. No partial parse is returned on failure. The internal field-policy hook uses :duplicate_key when a key required to be unique repeats before dictionary deduplication. :duplicate_parameter rejects repeated parameter names when the signature parsing policy requires uniqueness.