oven-sh/bun · error · Error

Required argument ${name} cannot follow an optional argument

Error message

Required argument ${name} cannot follow an optional argument

What it means

Error "Required argument ${name} cannot follow an optional argument" thrown in oven-sh/bun.

Source

Thrown at src/codegen/bindgen-lib-internal.ts:843

  return func;
}

function validateVariant(variant: any) {
  let minRequiredArgs = 0;
  let seenOptionalArgument = false;
  let i = 0;

  for (const [name, type] of Object.entries(variant.args) as [string, TypeImpl][]) {
    if (!(type instanceof TypeImpl)) {
      throw new Error(`Expected type for argument ${name}, got ${inspect(type)}`);
    }
    i += 1;
    if (type.isVirtualArgument()) {
      continue;
    }
    if (!type.flags.optional && !("default" in type.flags)) {
      if (seenOptionalArgument) {
        throw new Error(`Required argument ${name} cannot follow an optional argument`);
      }
      minRequiredArgs++;
    } else {
      seenOptionalArgument = true;
    }
  }

  return { minRequiredArgs };
}

function snapshotCallerLocation(): string {
  const stack = new Error().stack!;
  const lines = stack.split("\n");
  let i = 1;
  for (; i < lines.length; i++) {
    if (!lines[i].includes(import.meta.dir)) {
      return lines[i];
    }

View on GitHub (pinned to 8c5296ac45)

When it happens

Trigger: Thrown at src/codegen/bindgen-lib-internal.ts:843 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of oven-sh/bun@8c5296ac45 (2026-08-16). Data as JSON: /api/errors/1e99192d48a7eefb. Report an issue: GitHub.