Make c++ defer looks like a swift one

include/swift/Basic/Defer.h

@@ -18,11 +18,12 @@
 #ifndef __SWIFT_DEFER_H
 #define __SWIFT_DEFER_H
 
+#include <type_traits>
+
 namespace swift {
   template <typename F>
   class DoAtScopeExit {
     F &Fn;
-    DoAtScopeExit(DoAtScopeExit&) = delete;
     void operator=(DoAtScopeExit&) = delete;
   public:
     DoAtScopeExit(F &Fn) : Fn(Fn){}
@@ -30,8 +31,17 @@ namespace swift {
       Fn();
     }
   };
+
+  namespace detail {
+    struct DeferTask {};
+    template<typename F>
+    DoAtScopeExit<typename std::decay<F>::type> operator+(DeferTask, F&& fn) {
+      return DoAtScopeExit<typename std::decay<F>::type>(fn);
+    }
+  }
 }
 
+
 #define DEFER_CONCAT_IMPL(x, y) x##y
 #define DEFER_MACRO_CONCAT(x, y) DEFER_CONCAT_IMPL(x, y)
 
@@ -39,16 +49,13 @@ namespace swift {
 /// This macro is used to register a function / lambda to be run on exit from a
 /// scope.  Its typical use looks like:
 ///
-///   defer([&]{
+///   defer {
 ///     stuff
-///   })
+///   };
 ///
-#define defer(x) \
-  auto DEFER_MACRO_CONCAT(defer_func, __LINE__) = (x); \
-  swift::DoAtScopeExit<decltype(DEFER_MACRO_CONCAT(defer_func, __LINE__))> \
-       DEFER_MACRO_CONCAT(defer_local, __LINE__)\
-       (DEFER_MACRO_CONCAT(defer_func, __LINE__));
+#define defer \
+  auto DEFER_MACRO_CONCAT(defer_func, __COUNTER__) = \
+       ::swift::detail::DeferTask() + [&]()
 
 #endif
 
-