HHVM 4.33 is released! This release marks the end of support for 4.27; 4.28–4.32 remain supported, as does the 4.8 LTS release.


  • For developers working on the implementation of Hack itself (in rust/ocaml):
    • the test suite now passes in open source builds
    • the code generation tools for updating the parser and rust/ocaml FFI are now usable in opensource builds

Breaking Changes

  • Fixed issue where some FIXMEs had no effect on the code they were attached to instead having action-at-a-distance. This could lead to errors being reported in the wrong file. This bugfix may require fixmes to be added or moved.
  • An error is now raised if a reified function call is made without all required generics; for example, foo<vec>() now raises an error, as vec requires a generic type
  • Type structures for type aliases are now keyed by opaqueness and the alias name. In previous versions, if multiple types/type aliases resolved to the same concrete type, the wrong type structure would sometimes be returned - for example, with newtype FOO = int;, it was previously unpredicable if the type stucture for new MyClass<FOO>() would return the type alias information or not, and new MyClass<int>() could return FOO’s type alias information. The correct type structure will now consistently be returned. This only affects classes with reified generics - functions using reified generics are unaffected