HHVM 4.17 is released! This release marks the end of support for 4.11; 4.12-4.16 remain supported, as do the LTS releases 3.30 and 4.8.

Highlights

Reified generics are now supported. See full documentation and migration guide.

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function foo<reify T>(T $arg): void { ... }

foo<int>(42);
foo<string>(42);  // now a runtime error

Reified generic types can be used in the function code:

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abstract class BaseClass {
  abstract public function foo(): void;
}

// Before:
function bar(classname<BaseClass> $classname): void {
  $classname::foo();
}

// After:
function bar<reify T as BaseClass>(): void {
  T::foo();
}

Also see how to test and assert reified generic types and how to create new instances of reified generic classes.