As an illustration
When the Type is placed in keyof, it results in never.
type T = {
items?: string[] | undefined;
'items.0.kind'?: string[] | undefined;
'items.0.institution'?: string[] | undefined;
'items.0.started_at'?: string[] | undefined;
'items.0.finished_at'?: string[] | undefined;
'items.0.specialization'?: string[] | undefined;
'items.0.qualification'?: string[] | undefined;
} | {
user_is_blocked?: string[] | undefined;
jwt_token_is_invalid?: string[] | undefined;
jwt_token_is_expired?: string[] | undefined;
}
type Keys = keyof T // === never