IntelliSense for clang-cl produces incorrect error with boost::function

Type: LanguageService

Describe the bug

• OS and Version: Windows 10 Pro 1909
• VS Code Version: 1.51.0
• C/C++ Extension Version: 1.1.0

When I specify the path to clang-cl.exe to compilerPath property of c_cpp_properties.json, incorrect errors appear in the problems window. Using boost::function is an easy way to reproduce it.

Steps to reproduce

1. Make sure you have installed Clang 9.0.0 for Windows
2. Download Boost 1.73.0 from https://www.boost.org and extract it somewhere
3. Create a directory
4. Put test.cpp in the directory

#include <boost/function.hpp>

void f(const boost::function<void()> &x) {
    x();
}

5. Put .vscode/c_cpp_properties.json

{
    "version": 4,
    "configurations": [
        {
            "name": "Clang",
            "compilerPath": "C:/Program Files/LLVM/bin/clang-cl.exe",
            "includePath": [
                "C:/your/path/to/boost_1_73_0"
            ]
        }
    ]
}

6. Open the directory with VSCode
7. Open test.cpp with the editor

Expected behavior

No error is shown in the problems window. You can get this result by specifying clang.exe instead of clang-cl.exe.

Actual behavior

The following error is shown in the problems window.

call of an object of a class type without appropriate operator() or conversion functions to pointer-to-function type

Reproduce the diagnostic with the provided test.cpp, Boost 1.73.0, and .vscode/c_cpp_properties.json using clang-cl.exe, then compare it with clang.exe. Trace the IntelliSense language-service handling of the compilerPath setting; done means the boost::function example produces no Problems-window error with clang-cl.