Flow can now detect unused Promises

:::info[Historical] This post announced unused Promise detection when it was introduced. For current syntax and behavior, see the Linting documentation. :::

As of v0.201.0, Flow can now lint against unused/floating Promises. Unused promises can be dangerous, because errors are potentially unhandled, and the code may not execute in the intended order. They are usually mistakes that Flow is perfectly positioned to warn you about.