no-unnecessary-type-constraint

Disallow unnecessary constraints on generic types.

✅

Extending "plugin:@typescript-eslint/recommended" in an ESLint configuration enables this rule.

💡

Some problems reported by this rule are manually fixable by editor suggestions.

Generic type parameters (<T>) in TypeScript may be "constrained" with an extends keyword. When no extends is provided, type parameters default a constraint to unknown. It is therefore redundant to extend from any or unknown.

.eslintrc.cjs

module.exports = {
  "rules": {
    "@typescript-eslint/no-unnecessary-type-constraint": "error"
  }
};

Try this rule in the playground ↗

Examples

❌ Incorrect

interface FooAny<T extends any> {}

interface FooUnknown<T extends unknown> {}

type BarAny<T extends any> = {};

type BarUnknown<T extends unknown> = {};

class BazAny<T extends any> {
  quxAny<U extends any>() {}
}

const QuuxAny = <T extends any>() => {};

function QuuzAny<T extends any>() {}

✅ Correct

interface Foo<T> {}

type Bar<T> = {};

class Baz<T> {
  qux<U> { }
}

const Quux = <T>() => {};

function Quuz<T>() {}

Options

This rule is not configurable.

When Not To Use It

If you don't care about the specific styles of your type constraints, or never use them in the first place, then you will not need this rule.

Resources

• Rule source
• Test source