silphius/app/astride/evaluators/member.js

export default function(node, {evaluate, scope}) {
  const {computed, object, optional, property} = node;
  const member = (O, P) => (optional ? O?.[P] : O[P]);
  const O = evaluate(object, {scope});
  const P = computed
    ? evaluate(property, {scope})
    // Otherwise, identifier
    : {value: property.name};
  if (O.async || P.async) {
    return {
      async: true,
      value: Promise.all([O.value, P.value]).then(([O, P]) => member(O, P)),
    };
  }
  return {async: false, value: member(O.value, P.value)};
}