From fa7aa6446b53d4fba520ae8d3965117752d2d3b4 Mon Sep 17 00:00:00 2001
From: Mathew Sutcliffe <oktal3700@gmail.com>
Date: Wed, 25 May 2016 19:25:52 +0100
Subject: [PATCH] refs #662 Work around MSVC2015 bug causing failure to detect
 getLogCategories() in some conditions.

---
 src/blackmisc/typetraits.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/src/blackmisc/typetraits.h b/src/blackmisc/typetraits.h
index 5ccce43c6..4c3f1b6e7 100644
--- a/src/blackmisc/typetraits.h
+++ b/src/blackmisc/typetraits.h
@@ -46,6 +46,21 @@ namespace BlackMisc
     struct HasToQString<T, void_t<decltype(std::declval<T>().toQString())>> : public std::true_type {};
     //! \endcond
 
+#ifdef Q_CC_MSVC // work around what seems to be an expression SFINAE bug in MSVC
+    namespace Private
+    {
+        struct HasGetLogCategoriesHelper
+        {
+            struct Base { int getLogCategories; };
+            template <typename T> struct Derived : public T, public Base {};
+            template <typename T, T> struct TypeCheck {};
+            template <typename T> static std::false_type test(TypeCheck<decltype(&Base::getLogCategories), &Derived<T>::getLogCategories> *);
+            template <typename T> static std::true_type test(...);
+        };
+    }
+    template <typename T>
+    using HasGetLogCategories = decltype(Private::HasGetLogCategoriesHelper::test<T>(nullptr));
+#else
     /*!
      * Trait to detect whether a class T has a static member function named getLogCategories.
      */
@@ -55,6 +70,7 @@ namespace BlackMisc
     template <typename T>
     struct HasGetLogCategories<T, void_t<decltype(T::getLogCategories())>> : public std::true_type {};
     //! \endcond
+#endif
 
     /*!
      * Trait to detect whether a class T can be used as a key in a QHash.