HHVM 4.29 is released! This release marks the end of support for 4.23; 4.24–4.28 remain supported, as do the LTS releases 3.30 and 4.8.


  • Error messages now strip HH\ from names that are automatically imported into every namespace
  • Fixed .hack files not being correctly indexed by some IDE features
  • Shape key autocomplete now detects pre-existing quotes, avoiding completions such as $someshape['somekey''] with two apostrophes; this was most common with IDEs configured to automatically insert matching quotation marks.
  • Added RuntimeOption::CheckIntOverflow option:
    • if 0 (the default), overflows will silently wrap; this setting has the best performance
    • if 1, overflows will wrap and warn
    • if 2, overflows will throw an exception
  • Autocomplete now downranks magic methods and functions/methods with DO_NOT_USE in the name

Breaking Changes

  • $c->toVector(), $c->toSet(), $c->toMap() have been removed from Hack collections; use new Vector($c) etc or Hack Arrays instead; this is because they are not type-safe, as variance checks were added for generics
  • auto-imported reserved names (e.g. ‘self’) are now case-sensitive at runtime
  • Set::zip() now returns Set<nothing>, as pairs can not be stored in Sets; this could lead to new type errors in code that would previously fail at runtime. Similar changes have been made to ImmSet and other related classes
  • unserialize() no longer creates references; if old serialized data containing references is used, the referenced value will be copied instead
  • references are no longer supported by the parser
  • the runtime and typechecker now agree that Awaitable’s fully-qualified name is HH\Awaitable; it remains autoimported. In previous releases, the runtime considered it to be HH\Awaitable, but the typechecker considered it to be \Awaitable
  • it is now an error to pass a superglobal as inout
  • array (without generics) is now considered to be the union of array<_> (a.k.a varray) and array<_, _> (a.k.a. darray); this can lead to stricter handling of key (example 1, example 2)