Base class members are not displayed correctly using natvis files (LLDB)

Hi,

Under MacOS with LLDB, natvis fails to resolve base class member expressions, generating an error message instead. For example, given the code:

class ClassA
{
public:
  int intVal;
};

class ClassB : public ClassA
{
public:
};

int main()
{
  ClassB b;
  b.intVal = 42;
}

ClassB will not resolve the member expression intVal when used in a natvis file.

Attached is a small example project highlighting the issue. Note that this project also highlights anonymous structure and union issues with and without natvis under LLDB (see comments at the top of main.cpp for details) reported here.

Windows 10 + CDB (Visual Studio 2017). Works as expected with and without natvis.
Ubuntu 16.04 + GDB 7.11.1. Works without natvis, generates expression errors with.
MacOS 10.12.6 + LLDB 370.0.42 (XCode 8.3.2 installed). Fails with or without natvis.

vscode-natvis.zip

Start with the attached vscode-natvis.zip, especially main.cpp and the natvis example, and reproduce the base-class member expression failure under LLDB on macOS. Done means the ClassB natvis expression resolves intVal without an expression error, while preserving the reported behavior on the other debugger configurations.