# @typescript-eslint/unified-signatures

> Disallow overloads that can be written as one signature

Two overloads that return the same type and differ in one parameter say the same thing as one signature with a union type or an optional parameter. The overloads are longer, and they're also stricter than they look. A caller that has a `string | number` matches neither `(id: string)` nor `(id: number)`.

Overloads that return different types aren't reported.

{/* Generated by src/codegen/lint-rule-docs.ts. Do not edit this section. */}

## Configure

Off by default. To turn it on:

```toml bunfig.toml
[lint.rules]
"@typescript-eslint/unified-signatures" = "error" # or "warn"
```

Every option, set to its default:

```toml bunfig.toml
[lint.rules]
"@typescript-eslint/unified-signatures" = ["error", {
  ignoreDifferentlyNamedParameters = false,
  ignoreOverloadsWithDifferentJSDoc = false,
}]
```

{/* End of the generated section. */}

## Examples

Reported:

{/* bad {"count": 2} */}
```ts
function find(id: string): void;
function find(id: number): void;
function find(id: string | number) {}

interface Logger {
  log(message: string): void;
  log(message: string, level: number): void;
}
```

Not reported:

{/* good */}
```ts
function find(id: string | number): void {}

interface Logger {
  log(message: string, level?: number): void;
}

interface Parser {
  parse(text: string): object;
  parse(bytes: Uint8Array): Promise<object>;
}
```

## Options

| Option | Default | What it does |
| --- | --- | --- |
| `ignoreDifferentlyNamedParameters` | `false` | Don't report overloads where the parameters at the same position have different names. |
| `ignoreOverloadsWithDifferentJSDoc` | `false` | Don't report overloads that have different `/** */` comments. |

Different names often mean different things, which one signature can't say. Not reported with `ignoreDifferentlyNamedParameters`:

{/* good {"options": [{"ignoreDifferentlyNamedParameters": true}]} */}
```ts
interface Users {
  remove(id: number): void;
  remove(email: string): void;
}
```

The same goes for overloads that are documented separately. Not reported with `ignoreOverloadsWithDifferentJSDoc`:

{/* good {"options": [{"ignoreOverloadsWithDifferentJSDoc": true}]} */}
```ts
interface Users {
  /** Removes the user with this ID. */
  remove(key: number): void;
  /** @deprecated Look up the ID first. */
  remove(key: string): void;
}
```