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no-useless-generics

Disallow type parameters that do not improve a declaration's type safety.

⚠️ This rule requires type information to run.

Targeted pattern scope​

This rule targets TypeScript signatures that declare generic type parameters.

What this rule reports​

This rule reports generic parameters that do not provide meaningful type relationships.

Why this rule exists​

Redundant generic parameters add cognitive overhead and can mislead readers into thinking polymorphism is required when it is not. This rule reports unnecessary generic type parameters.

❌ Incorrect​

function toUpper<T>(value: string): string {
 return value.toUpperCase();
}

✅ Correct​

function identity<T>(value: T): T {
 return value;
}

Behavior and migration notes​

This rule forwards options to @typescript-eslint/no-unnecessary-type-parameters.

Additional examples​

function parse<T extends string>(input: string): string {
 return input.trim();
}
// ❌ reported: generic does not add a relation

function first<T>(items: readonly T[]): T | undefined {
 return items[0];
}
// ✅ valid: generic ties parameter and return type

ESLint flat config example​

import etcMisc from "eslint-plugin-etc-misc";

export default [
 {
  plugins: { "etc-misc": etcMisc },
  rules: {
   "etc-misc/no-useless-generics": "error",
  },
 },
];

When not to use it​

Disable this rule if your API surface intentionally keeps placeholder type parameters for generated declarations or staged migrations.

Package documentation​

Rule catalog ID: R050

Further reading​

Adoption resources​

  • Start at warning level in CI, then move to error after cleanup.
  • Use focused codemods/autofix batches per package or directory.