Function has

packages/effect/src/internal/core.ts:671–673

(target, p)

  if (Option.isSome(span)) {
    return new Proxy(obj, {
      has(target, p) {
        return p === internalCause.spanSymbol || p === originalSymbol || p in target
      },
      get(target, p) {
        if (p === internalCause.spanSymbol) {
          return span.value