Nested typedef incorrectly placed in a namespace

[mkucmpro]

Describe the bug
When my C++ header contains nested typedef, like so (header.hpp):

#pragma once

#include <functional>

class Foo {
public:
  typedef std::function<void(int)> CallbackType; // <-- this is the problem
  explicit Foo(const CallbackType &cb) {}
};

Any my bindings use it (main.rs):

use autocxx::prelude::*;

include_cpp!(
    #include "header.hpp"
    safety!(unsafe_ffi)
    generate!("Foo")
);

Then cargo build fails, because it places CallbackType inside a namespace Foo like so:

namespace Foo {
  using CallbackType = ::Foo::CallbackType;
}

And then C++ compilation fails with:
target\debug\build\rust-autocxx-b49661854cba97fb\out\autocxx-build-dir\cxx\gen0.cxx(147): error C2757: 'Foo': a symbol with this name already exists and therefore this name cannot be used as a namespace name

To Reproduce
Use src/header.hpp, src/main.rs and build.rs:

fn main() {
    autocxx_build::Builder::new(&"src/main.rs", &[&"src"])
        .build()
        .expect("Unable to build C++ bindings")
        .compile("autocxx-demo"); 
    println!("cargo:rerun-if-changed={}", "src/main.rs");
}

Expected behavior
Rust binding correctly generated, no C++ compilation error

Additional context
None