System Workbench for STM32

I'm trying to import a working mbed project in to the workbench but have an Error1 on build. I think I've tracked the problem to the BusOut class in mbed.
If I rem out the BusOut example there is no problem and the DigitalOut class works ok.

Any ideas please?

1. include "mbed.h"
2. include "TextLCD.h"
3. include "LEDs.h"

LEDs flash(PD_2,PC_12); // (LED1, LED2)

BusOut example(PC_5, PA_12, PA_11, PB_12);

int main() {

flash.invert_led1();
while(1) {
myled = 1; // LED is ON

wait(0.1); // 200 ms
myled = 0; // LED is OFF
wait(0.5); // 0.5 sec

flash.invert_led1();
flash.invert_led2();

//lcd.printf("Hello World!");
}
}