&gt; <i>I couldn&#x27;t help reading the emphasized &quot;types&quot; in &quot;optional types&quot; as a yell for the Typescript developers</i><p>Dart was saying this before it was cool!<p>Historically, Dart was (in part) born out of Gilad Bracha&#x27;s Pluggable Type Systems[1] paper, so the concept of optional types is the very heart of Dart, and was so long before TypeScript.<p>[1]: <a href="http:&#x2F;&#x2F;bracha.org&#x2F;pluggableTypesPosition.pdf" rel="nofollow">http:&#x2F;&#x2F;bracha.org&#x2F;pluggableTypesPosition.pdf</a>