PsiParameter[] parameters = psiMethod.getParameterList().getParameters();
if (parameters.length == 1) {
showUsages(mouseEvent, parameters[0]);
} else {
new PickTypeAction().startPickTypes(new RelativePoint(mouseEvent), parameters,
new PickTypeAction.Callback() {
@Override public void onParameterChosen(PsiParameter selected) {
showUsages(mouseEvent, selected);
}
});