ART: Use static_assert in down_cast

Use C++11 to write an actual compile-time assert.

Change-Id: I36bd94adbf6c732e103720308e1e6bf11065f474

1 files changed, 4 insertions, 9 deletions

diff --git a/runtime/base/casts.h b/runtime/base/casts.h
index be94c2eb78..138c2fda80 100644
--- a/runtime/base/casts.h
+++ b/runtime/base/casts.h
@@ -19,6 +19,8 @@
 
 #include <assert.h>
 #include <string.h>
+#include <type_traits>
+
 #include "base/macros.h"
 
 namespace art {
@@ -65,16 +67,9 @@ inline To implicit_cast(From const &f) {
 
 template<typename To, typename From>     // use like this: down_cast<T*>(foo);
 inline To down_cast(From* f) {                   // so we only accept pointers
-  // Ensures that To is a sub-type of From *.  This test is here only
-  // for compile-time type checking, and has no overhead in an
-  // optimized build at run-time, as it will be optimized away
-  // completely.
-  if (false) {
-    implicit_cast<From*, To>(0);
-  }
+  static_assert(std::is_base_of<From, typename std::remove_pointer<To>::type>::value,
+                "down_cast unsafe as To is not a subtype of From");
 
-  //
-  // assert(f == NULL || dynamic_cast<To>(f) != NULL);  // RTTI: debug mode only!
   return static_cast<To>(f);
 }