/** The function instance itself. */
private final Function mFunc;
public FnSymbol(String name, Function func, Type retType, List<Type> argTypes,
List<Type> varArgTypes) {
super(name, new FnType(retType, argTypes, varArgTypes));
mFunc = func;
mRetType = retType;
mArgTypes = argTypes;
mVarArgTypes = varArgTypes;
}