@facebook-github-bot facebook-github-bot released this Dec 8, 2018 · 271 commits to master since this release

Assets 7

Likely to cause new Flow errors:

  • Made Function and Object types be aliases for any. They were always unsafe types, just like any, but they had peculiar behavior. This change revealed places where they were handled improperly within Flow, and ended up surfacing type errors that were previously missed.

New Features:

  • Added the experimental Watchman lazy mode (flow start --lazy-mode watchman). This improves the lazy mode experience for repositories which use Mercurial and Watchman. We will document it more when/if it proves itself.
  • Added flow config check which validates the .flowconfig.


  • Made miscellaneous improvements to the AST differ, which improves the output of global rename.
  • Made .flowconfig parsing less strict (in particular, if the --ignore-version flag is passed, do not fatal on unrecognized config options).
  • Performed a code cleanup in type normalization that caused some types in type-at-pos to be displayed differently.
  • Removed redundant information in stored ASTs resulting in a modest reduction in memory usage.
  • Flow assigns long string literals type string, rather than the singleton type of that literal. Now, this fact is surfaced in error messages.
  • Fixed stack overflows:
    • When checking a large number of files.
    • When a large number of errors are present.


  • Added React.Suspense.
  • Removed React.useMutationEffect hook.