Depend on HHVM 4

composer.json

@@ -3,9 +3,9 @@
     "description": "Hack Codegen is a library for programatically generating Hack code",
     "keywords": ["code generation", "Hack"],
     "require": {
-        "hhvm": ">=3.28.0",
-        "hhvm/hhvm-autoload": "^1.6",
-        "hhvm/hsl": "^3.28.0"
+        "hhvm": "^4.0.0",
+        "hhvm/hhvm-autoload": "^2.0",
+        "hhvm/hsl": "^4.0"
     },
     "bin": [ "bin/hh-codegen-verify-signatures" ],
     "authors": [
@@ -35,7 +35,7 @@
         "hhvm/hacktest": "^1.0",
         "hhvm/type-assert": "^3.1",
         "facebook/fbexpect": "^2.1.0",
-        "hhvm/hhast": "^3.28.0",
+        "hhvm/hhast": "^4.0",
         "facebook/difflib": "^1.0"
     }
 }