Update HHVM version to a supported version

Summary: Pull Request resolved: hhvm#21

Differential Revision: D16267042

fbshipit-source-id: 82b45ce904304351d2409098f9ef445ee241d0e9

Author: lexidor

.hhconfig

@@ -2,3 +2,6 @@ assume_php=false
 disable_primitive_refinement=true
 disallow_stringish_magic=true
 user_attributes=
+disallow_ambiguous_lambda=true
+disable_unsafe_expr=true
+disable_unsafe_block=true

.travis.yml

@@ -2,7 +2,6 @@ sudo: required
 language: generic
 services: docker
 env:
- - HHVM_VERSION=4.7-latest
  - HHVM_VERSION=4.8-latest
  - HHVM_VERSION=latest
  - HHVM_VERSION=nightly

composer.json

@@ -7,7 +7,7 @@
       }
     },
     "require": {
-        "hhvm": "^4.7",
+        "hhvm": "^4.8",
         "hhvm/hsl": "^4.0"
     },
     "require-dev": {

src/StringDiff.php

@@ -137,7 +137,7 @@ private function getUnifiedDiffHunk(
     invariant($old_start !== null, 'failed to find an old pos');
     invariant($new_start !== null, 'failed to find a new pos');
 
-    $format = ($start, $lines) ==> ($start === 1 && $lines === 1)
+    $format = (int $start, int $lines) ==> ($start === 1 && $lines === 1)
       ? '1'
       : Str\format('%d,%d', $start, $lines);