From: Hans Fugal <fugalh@fb.com>
Date: Thu, 2 Jul 2015 18:43:42 +0000 (-0700)
Subject: nice error message if you try to Future<void>
X-Git-Tag: v0.49.0~6
X-Git-Url: http://plrg.eecs.uci.edu/git/?p=folly.git;a=commitdiff_plain;h=8fe0a63e56fa5e9999d6cb793a0b8ddb31241c73

nice error message if you try to Future<void>

Summary: If you try to make a future or promise of `void`, you will get this nice error message telling you to use `Unit` instead.

Reviewed By: @djwatson

Differential Revision: D2211239
---

diff --git a/folly/futures/detail/Core.h b/folly/futures/detail/Core.h
index f0018862..a01285fa 100644
--- a/folly/futures/detail/Core.h
+++ b/folly/futures/detail/Core.h
@@ -74,6 +74,8 @@ enum class State : uint8_t {
 /// time there won't be any problems.
 template<typename T>
 class Core {
+  static_assert(!std::is_void<T>::value,
+                "void futures are not supported. Use Unit instead.");
  public:
   /// This must be heap-constructed. There's probably a way to enforce that in
   /// code but since this is just internal detail code and I don't know how