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@facebook-github-bot facebook-github-bot released this Nov 12, 2019 · 100 commits to master since this release

Likely to cause new Flow errors:

  • JSX expressions now use the new spread semantics added in v0.111.0
  • Attempting to write to or update a read-only property using operator assignment is now a type error

New Features:

  • New ambiguous-object-type lint warning against use of {} object types (prefer {||} or {...} instead, even when exact-by-default is enabled).
  • Improved support for optional chaining

Notable bug fixes:

  • Malformed type annotations no longer trigger the unclear-type lint error
  • Builtin classes can no longer be extended


  • Improved performance for utility types and refinements in unions
  • Various improvements to autocomplete and get-def IDE services
  • Add useDeferredValue and useTransition to React library definitions
  • Add bytesWritten funciton to library definition (thanks @farzonl)
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