Fix type assertions for array-like interfaces

Without this we could infer that an array was an object,
skip the guards, and then die horribly.

hphp/compiler/analysis/alias_manager.cpp

@@ -64,6 +64,8 @@
 #include "hphp/compiler/analysis/live_dict.h"
 #include "hphp/compiler/analysis/ref_dict.h"
 
+#include "hphp/runtime/base/builtin_functions.h"
+
 #include "hphp/util/parser/hphp.tab.hpp"
 #include "hphp/util/parser/location.h"
 #include "hphp/util/util.h"
@@ -2638,6 +2640,10 @@ private:
     if (sv && se) {
       const string &s = se->getLiteralString();
       if (s.empty()) return ExpressionPtr();
+      if (interface_supports_array(s)) {
+        // This could be an array, so don't assert anything
+        return ExpressionPtr();
+      }
       TypePtr o(Type::CreateObjectType(Util::toLower(s)));
 
       // don't do specific type assertions for unknown classes

hphp/test/slow/type_assertions/array_like.php

@@ -0,0 +1,13 @@
+<?hh
+
+function foo(KeyedTraversable<String> $foo, $f) {
+  var_dump($foo);
+}
+
+function test($a) {
+  if ($a instanceof KeyedTraversable) {
+    foo($a, false);
+  }
+}
+
+test(array(1));

hphp/test/slow/type_assertions/array_like.php.expect

@@ -0,0 +1,4 @@
+array(1) {
+  [0]=>
+  int(1)
+}