When trying to use SPIFFS I'm getting errors when trying to access specific functions. Compiler says they do not exist. Such as write and read on the file objects. These compile find in the Arduino environment.

Also, can not use FILE at all, while I can enter it into the source, later in the code when I try to use it the compiler complains that it has not been defined.

I tried to follow the errors and ended up in the FS.h file at the following line:
typedef std::shared_ptr<FileImpl> FileImplPtr;

One more quick question: Is there a way to upload files to the SPIFFS from VisualMicro? Similar to the plugin available for Arduino.exe? 

Thanks!

Ohh. current VisualMicro version: 1.1603.20 - 427

Turned out to be a missing menu item. Thanks for the nudge. Sorry for the delay.

You should see a "vMicro>Publish Data Files" menu item when ESP8266 or Arduino Yun boards are selected.

The files found in a "[Project]\Data" sub folder are uploaded regardless of which files are "Included" in the "Solution Explorer".

Intellisense was using the wrong cplusplus version so the File and SPIFFS commands should work nicely now.

Latest release is 1606.17 Sp3 please see the Release Notes for more information