ts-r
  • Error
  • Reported by the type checker

TS2386

Overload signatures must all be optional or required.

Overloads of a method or property disagree on whether it is optional. Mark all of them with ? or none of them.

What it means

An overloaded method declares one member. Writing ? on some of its signatures and not on others asks for a member that is both optional and required, which is reported on the signature that differs.

Example

index.ts
export class Store {
  get(key: string): string;
  get?(key: number): string;
  get(key: string | number): string {
    return String(key);
  }
}
ts-r-check -p tsconfig.json --pretty false ts-r output
index.ts(3,3): error TS2386: Overload signatures must all be optional or required.

Recorded by node scripts/verify-examples.mjs with ts-r built from commit 6deaf01. The example uses the default tsconfig: strict, target: es2022, module: esnext, moduleResolution: bundler.

How to fix

  • Put ? on every signature of the member, or on none.
  • If one form really is optional, give it a separate name.