From 8b4784cf2fd3e2561f7d6182d7686b0bc3c9340d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vladim=C3=ADr=20Vondru=C5=A1?= <mosra@centrum.cz>
Date: Wed, 25 Jul 2018 23:39:12 +0200
Subject: [PATCH] Trade: MSVC workarounds.

I almost forgot those were still a thing.
---
 src/Magnum/Trade/AbstractImporter.h | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/Magnum/Trade/AbstractImporter.h b/src/Magnum/Trade/AbstractImporter.h
index aa6c3867e..7c178336a 100644
--- a/src/Magnum/Trade/AbstractImporter.h
+++ b/src/Magnum/Trade/AbstractImporter.h
@@ -1114,10 +1114,12 @@ class MAGNUM_TRADE_EXPORT AbstractImporter: public PluginManager::AbstractManagi
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
 template<class Callback, class T> void AbstractImporter::setFileCallback(Callback callback, T& userData) {
-    /* Don't try to wrap a null function pointer */
-    if(!callback) return setFileCallback(nullptr);
+    /* Don't try to wrap a null function pointer. Need to cast first because
+       MSVC (even 2017) can't apply ! to a lambda. Ugh. */
+    const auto callbackPtr = static_cast<Containers::ArrayView<const char>(*)(const std::string&, ImporterFileCallbackPolicy, T&)>(callback);
+    if(!callbackPtr) return setFileCallback(nullptr);
 
-    _fileCallbackTemplate = { reinterpret_cast<void(*)()>(static_cast<Containers::ArrayView<const char>(*)(const std::string&, ImporterFileCallbackPolicy, T&)>(callback)), &userData };
+    _fileCallbackTemplate = { reinterpret_cast<void(*)()>(callbackPtr), &userData };
     setFileCallback([](const std::string& filename, const ImporterFileCallbackPolicy flags, void* const userData) {
         auto& s = *reinterpret_cast<FileCallbackTemplate*>(userData);
         return reinterpret_cast<Containers::ArrayView<const char>(*)(const std::string&, ImporterFileCallbackPolicy, T&)>(s.callback)(filename, flags, *static_cast<T*>(s.userData));