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@facebook-github-bot facebook-github-bot released this Jun 11, 2019 · 170 commits to master since this release

Likely to cause new Flow errors:

  • $Keys now produces a more precise type, which may find errors where incompatible strings were passed to something expecting the $Keys of some object.

New Features:

  • We released a new implicit-inexact-object lint to detect when an inexact object is used without explicitly adding ... to the
    end of the props list. See here for context.
  • Function type parameters may now use default arguments. This is not yet supported by babel.

Notable bug fixes:

  • Fixed a bug with ranges returned by autocomplete
  • Fixed a bug where errors with bad locations reported over the LSP could cause the editor to clear all errors.


  • React.memo and React.lazy now both allow you to specify an instance type via React.AbstractComponent.
  • Various performance improvements to union types.
  • Various libdef fixes and improvements.
  • Various improvements to error positioning.
  • The recursion limit is now configurable in the .flowconfig via recursion_limit. Most projects will not need to override this value.


  • Forbid private fields named #constructor
  • Fix duplicate private class field validation for getters/setters
  • Fix parsing of private getters and setters
  • Function type parameters may now use default arguments.
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