Compiler Error C3550
only plain 'decltype(auto)' is allowed in this context
If decltype(auto) is used as a placeholder for the return type of a function, it must be used by itself. It cannot be used as part of a pointer declaration (decltype(auto)*), a reference declaration (decltype(auto)&), or any other such qualification.
Example
The following sample generates C3550:
// C3550.cpp
// compile with: /c
decltype(auto)* func1(); // C3550
decltype(auto)& func2(); // C3550
decltype(auto)&& func3(); // C3550
auto* func4(); // OK
To resolve the error remove all illegal qualification on decltype(auto). For instance, decltype(auto)* func1() can be turned into auto* func1().