Confusing error regarding `result` from VC++ when making a continuable from a lambda that captures a variable called `result`

@Naios

Using Continuable 4.1.0

Reproduction steps:

Launch Visual Studio 2019 native tools command prompt
Create folder somewhere and switch to it
```
mkdir C:\temp\bug55
cd /d C:\temp\bug55
```

Change to folder and clone Continuable

git clone --recursive https://github.com/naios/continuable

Create test.cpp with the following contents (e.g., via copy con test.cpp)

#include <continuable/continuable.hpp>
static void Test() {
    int result = 0;
    cti::make_continuable<int>([result](auto&& promise) {});
}

Compile

cl /I .\continuable\include test.cpp /I .\continuable\dep\function2\function2\include

Note probably-unexpected error...

Microsoft (R) C/C++ Optimizing Compiler Version 19.29.30146 for x64
Copyright (C) Microsoft Corporation.  All rights reserved.

test.cpp
C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\VC\Tools\MSVC\14.29.30133\include\ppltasks.h(1571): warning C4530: C++ exception handler used, but unwind semantics are not enabled. Specify /EHsc
.\continuable\include\continuable/detail/core/base.hpp(143): error C2327: 'Test::<lambda_ce49853aebba6891891f5a54e1664ea4>::result': is not a type name, static, or enumerator
.\continuable\include\continuable/detail/core/base.hpp(168): note: see reference to class template instantiation 'cti::detail::base::proxy_continuable<hint_t,Test::<lambda_ce49853aebba6891891f5a54e1664ea4>>' being compiled
.\continuable\include\continuable/continuable-base.hpp(898): note: see reference to function template instantiation 'auto cti::detail::base::attorney::create_from<_Ty,cti::detail::identity<int>>(T &&,Hint,cti::detail::util::ownership)' being compiled
        with
        [
            _Ty=Test::<lambda_ce49853aebba6891891f5a54e1664ea4>,
            T=Test::<lambda_ce49853aebba6891891f5a54e1664ea4>,
            Hint=cti::detail::identity<int>
        ]
test.cpp(4): note: see reference to function template instantiation 'auto cti::make_continuable<int,Test::<lambda_ce49853aebba6891891f5a54e1664ea4>>(Continuation &&)' being compiled
        with
        [
            Continuation=Test::<lambda_ce49853aebba6891891f5a54e1664ea4>
        ]

In the end I tracked this down to captured variables in msvc apparently giving their lambda's type member variables of the same name. So result is a member variable on the base class for proxy_continuable in this case.

This feels like a msvc problem - looks like clang and gcc must rename the captured variables, or use some other mechanism? - but perhaps it's fixable. I'm afraid I stopped at C++14 so I have no specific suggestions. Maybe a note in the documentation would suffice.

Compiler Explorer example that I think narrows it down to the issue: https://godbolt.org/z/7qz4sd7sT

Thanks,

--Tom

Naios / continuable

Confusing error regarding `result` from VC++ when making a continuable from a lambda that captures a variable called `result` #55