inplace_function: Add a missing std::forward.

The missing `forward` around these `args...` was preventing the noexcept
specifier from compiling for wrapped types that took non-copyable argument
types (such as `unique_ptr`).

Fixes #154.

SG14/inplace_function.h

@@ -101,9 +101,9 @@ template<typename R, typename... Args> struct vtable
 
     template<typename C> explicit constexpr vtable(wrapper<C>) noexcept :
         invoke_ptr{ [](storage_ptr_t storage_ptr, Args&&... args)
-            noexcept(noexcept(std::declval<C>()(args...))) -> R
+            noexcept(noexcept(std::declval<C>()(static_cast<Args&&>(args)...))) -> R
             { return (*static_cast<C*>(storage_ptr))(
-                std::forward<Args>(args)...
+                static_cast<Args&&>(args)...
             ); }
         },
         copy_ptr{ [](storage_ptr_t dst_ptr, storage_ptr_t src_ptr)

SG14_test/inplace_function_test.cpp

@@ -415,6 +415,20 @@ struct test_bug_32072 {
 static_assert(std::is_copy_constructible<test_bug_32072>::value, "");
 static_assert(std::is_nothrow_move_constructible<test_bug_32072>::value, "");
 
+static void RvalueRefParameter()
+{
+    stdext::inplace_function<void(std::unique_ptr<int>&&)> f;
+    f = [](std::unique_ptr<int>) {};
+    f = [](std::unique_ptr<int>&&) {};
+    f = [](const std::unique_ptr<int>&) {};
+    f(std::make_unique<int>(42));
+    stdext::inplace_function<void(std::unique_ptr<int>)> g;
+    g = [](std::unique_ptr<int>) {};
+    g = [](std::unique_ptr<int>&&) {};
+    g = [](const std::unique_ptr<int>&) {};
+    g(std::make_unique<int>(42));
+}
+
 void sg14_test::inplace_function_test()
 {
     // first set of tests (from Optiver)
@@ -427,6 +441,7 @@ void sg14_test::inplace_function_test()
     ContainingStdFunction();
     SimilarTypeCopy();
     FunctorDestruction();
+    RvalueRefParameter();
 
     // second set of tests
     using IPF = stdext::inplace_function<void(int)>;