unifiedSignatures

Reports function overloads that could be unified.

✅ This rule is included in the ts stylistic presets.

Function overloads that differ only by a single parameter type or by optional parameters can be simplified using union types or optional parameters.

Examples

Union Types

❌ Incorrect

interface Parser {
  parse(input: string): Document;
  parse(input: Buffer): Document;
}

✅ Correct

interface Parser {
  parse(input: string | Buffer): Document;
}

Optional Parameters

❌ Incorrect

interface Logger {
  log(): void;
  log(message: string): void;
}

✅ Correct

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

Options

This rule is not configurable.

When Not To Use It

If you intentionally use separate overloads for different behaviors or documentation purposes, you may want to disable this rule.

Further Reading

• TypeScript: Function Overloads

Equivalents in Other Linters

• Biome: useUnifiedTypeSignatures
• ESLint: @typescript-eslint/unified-signatures