* @param coveredCoord Coordinates of field to reveal.
*/
void revealClearField(Coord coveredCoord) {
GUI_FIELD realValue = mRealMinefield.get(coveredCoord);
if (realValue.equals(GUI_FIELD.MINE)) {
throw new MinesSolverInternalError("Bad evaluation of clear "
+ " at coord " + coveredCoord);
}
signalToGUI(mFieldRevealedSignal, coveredCoord);
}