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@facebook-github-bot facebook-github-bot released this Aug 22, 2019 · 146 commits to master since this release

Likely to cause new Flow errors:

  • We're starting to make changes to how Flow models object spreads. For more see this announcement
  • Updated parsing of the experimental nullish coalescing ?? operator. It now has a lower precedence than || and &&, and parentheses are required to nest it with them.
  • Flow wasn't typechecking the properties of certain obscure JSX usage (namespaced identifiers, member expression with @jsx / @csx), so would miss type errors in their expressions (e.g. <a:b prop={"hello" * 10} /> now errors)

Notable bug fixes:

  • Fixed a bug where merge or check jobs would crash when a parse error was added to a file in a cycle. The crash was silent but unintended.
  • Types-first no longer ignores the munge_underscores flowconfig option


  • Various libdef updates. Thanks for all the PRs!


  • Improved error messages for missing semicolon
  • Comments are now correctly attached to break statements and array patterns
  • libflowparser now supports esproposal_nullish_coalescing as an option
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