When building with VisualGDB the compilation fails due to the lack of required include files Dir.h and File.h.
Compiler report:

1>------ Build started: Project: exported-mbed-STM32F429-nucleo, Configuration: Debug VisualGDB ------
1>  FileSystem.cpp
1>  mbed-os/features/filesystem/FileSystem.cpp: In instantiation of 'class Managed<mbed::File>':
1>  mbed-os\features\filesystem\FileSystem.cpp(141,19): note :   required from here
1>mbed-os\features\filesystem\FileSystem.cpp(130,7): error :  invalid use of incomplete type 'class mbed::File'
1>   class Managed : public F {
1>         ^~~~~~~
1>  mbed-os\features\filesystem\FileSystem.cpp(18):
1>  mbed-os\features\filesystem\FileSystem.h(39,7): note :  forward declaration of 'class mbed::File'
1>   class File;
1>         ^~~~
1>  mbed-os/features/filesystem/FileSystem.cpp: In member function 'virtual int mbed::FileSystem::open(mbed::FileHandle**, const char*, int)':
1>mbed-os\features\filesystem\FileSystem.cpp(141,19): error :  cannot convert 'Managed<mbed::File>*' to 'mbed::File*' in initialization
1>       File *f = new Managed<File>;
1>                     ^~~~~~~~~~~~~
1>mbed-os\features\filesystem\FileSystem.cpp(142,16): error :  invalid use of incomplete type 'class mbed::File'
1>       int err = f->open(this, path, flags);
1>                  ^~
1>  mbed-os\features\filesystem\FileSystem.cpp(18):
1>  mbed-os\features\filesystem\FileSystem.h(39,7): note :  forward declaration of 'class mbed::File'
1>   class File;
1>         ^~~~
1>mbed-os\features\filesystem\FileSystem.cpp(144,16): warning :  possible problem detected in invocation of delete operator: [-Wdelete-incomplete]
1>           delete f;
1>                  ^
1>mbed-os\features\filesystem\FileSystem.cpp(141,11): warning :  'f' has incomplete type
1>       File *f = new Managed<File>;
1>             ^
1>  mbed-os\features\filesystem\FileSystem.cpp(18):
1>  mbed-os\features\filesystem\FileSystem.h(39,7): note :  forward declaration of 'class mbed::File'
1>   class File;
1>         ^~~~
1>  mbed-os\features\filesystem\FileSystem.cpp(144,16): note :  neither the destructor nor the class-specific operator delete will be called, even if they are declared when the class is defined
1>           delete f;
1>                  ^
1>mbed-os\features\filesystem\FileSystem.cpp(148,13): error :  cannot convert 'mbed::File*' to 'mbed::FileHandle*' in assignment
1>       *file = f;
1>               ^
1>  mbed-os\features\filesystem\FileSystem.cpp(18):
1>  mbed-os\features\filesystem\FileSystem.h(39,7): note :  class type 'mbed::File' is incomplete
1>   class File;
1>         ^~~~
1>  mbed-os/features/filesystem/FileSystem.cpp: In instantiation of 'class Managed<mbed::Dir>':
1>  mbed-os\features\filesystem\FileSystem.cpp(153,18): note :   required from here
1>mbed-os\features\filesystem\FileSystem.cpp(130,7): error :  invalid use of incomplete type 'class mbed::Dir'
1>   class Managed : public F {
1>         ^~~~~~~
1>  mbed-os\features\filesystem\FileSystem.cpp(18):
1>  mbed-os\features\filesystem\FileSystem.h(38,7): note :  forward declaration of 'class mbed::Dir'
1>   class Dir;
1>         ^~~
1>  mbed-os/features/filesystem/FileSystem.cpp: In member function 'virtual int mbed::FileSystem::open(mbed::DirHandle**, const char*)':
1>mbed-os\features\filesystem\FileSystem.cpp(153,18): error :  cannot convert 'Managed<mbed::Dir>*' to 'mbed::Dir*' in initialization
1>       Dir *d = new Managed<Dir>;
1>                    ^~~~~~~~~~~~
1>mbed-os\features\filesystem\FileSystem.cpp(154,16): error :  invalid use of incomplete type 'class mbed::Dir'
1>       int err = d->open(this, path);
1>                  ^~
1>  mbed-os\features\filesystem\FileSystem.cpp(18):
1>  mbed-os\features\filesystem\FileSystem.h(38,7): note :  forward declaration of 'class mbed::Dir'
1>   class Dir;
1>         ^~~
1>mbed-os\features\filesystem\FileSystem.cpp(156,16): warning :  possible problem detected in invocation of delete operator: [-Wdelete-incomplete]
1>           delete d;
1>                  ^
1>mbed-os\features\filesystem\FileSystem.cpp(153,10): warning :  'd' has incomplete type
1>       Dir *d = new Managed<Dir>;
1>            ^
1>  mbed-os\features\filesystem\FileSystem.cpp(18):
1>  mbed-os\features\filesystem\FileSystem.h(38,7): note :  forward declaration of 'class mbed::Dir'
1>   class Dir;
1>         ^~~
1>  mbed-os\features\filesystem\FileSystem.cpp(156,16): note :  neither the destructor nor the class-specific operator delete will be called, even if they are declared when the class is defined
1>           delete d;
1>                  ^
1>mbed-os\features\filesystem\FileSystem.cpp(160,12): error :  cannot convert 'mbed::Dir*' to 'mbed::DirHandle*' in assignment
1>       *dir = d;
1>              ^
1>  mbed-os\features\filesystem\FileSystem.cpp(18):
1>  mbed-os\features\filesystem\FileSystem.h(38,7): note :  class type 'mbed::Dir' is incomplete
1>   class Dir;
1>         ^~~
1>  mbed-os/features/filesystem/FileSystem.cpp: In instantiation of 'int Managed<F>::close() [with F = mbed::Dir]':
1>  mbed-os\features\filesystem\FileSystem.cpp(162,1): note :   required from here
1>mbed-os\features\filesystem\FileSystem.cpp(133,27): error :  incomplete type 'mbed::Dir' used in nested name specifier
1>           int err = F::close();
1>                     ~~~~~~~~^~
1>  mbed-os/features/filesystem/FileSystem.cpp: In instantiation of 'int Managed<F>::close() [with F = mbed::File]':
1>  mbed-os\features\filesystem\FileSystem.cpp(162,1): note :   required from here
1>mbed-os\features\filesystem\FileSystem.cpp(133,27): error :  incomplete type 'mbed::File' used in nested name specifier
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========