// CHAR(PRINTNAME(symbol)));
// missing = R_GetVarLocMISSING(loc);
// val = R_GetVarLocValue(loc);
if(!next.hasTag()) {
throw new EvalException("closure formal has no tag! op = " + op);
}
Symbol symbol = next.getTag();
SEXP val = rho.findVariable(symbol);
if(val == Symbol.UNBOUND_VALUE) {
throw new EvalException("could not find symbol \"%s\" in the environment of the generic function", symbol.getPrintName());
}
// SET_FRAME(newrho, CONS(val, FRAME(newrho)));
// SET_TAG(FRAME(newrho), symbol);