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no-misused-generics

Disallow generic type parameters that cannot be inferred or that do not enforce a meaningful type relationship.

Targeted pattern scope​

⚠️ This rule requires type information to run. Configure type-aware linting (parserOptions.project or projectService) before enabling it.

This rule checks TypeScript signature declarations that declare generic type parameters, including:

  • function declarations and expressions,
  • arrow functions,
  • methods,
  • call/construct signatures,
  • function and constructor type signatures.

What this rule reports​

This rule reports type parameters when either of the following is true:

  • the type parameter cannot be inferred from any function parameter (cannotInfer), or
  • the type parameter is inferable but does not enforce a meaningful relationship and can be replaced by unknown (or its explicit constraint) (canReplace).

Why this rule exists​

Type parameters should encode real relationships between values and types. If a type parameter cannot be inferred, callers must always provide it manually. If it does not constrain behavior, it often adds complexity without extra safety.

❌ Incorrect​

declare function get<T>(): T;
declare function take<T>(value: T): void;

✅ Correct​

declare function identity<T>(value: T): T;
declare function compare<T>(left: T, right: T): boolean;
declare function compare<T, U extends T>(left: T, right: U): boolean;

Behavior and migration notes​

This rule has no options.

When this rule reports canReplace, replacing the type parameter with unknown (or with the explicit constraint) usually preserves intent while reducing generic noise.

Additional examples​

function wrap<T extends string>(value: T): void {
 console.log(value);
}
// ❌ reported with `canReplace`: `T` can be replaced with `string`

function pair<T>(left: T, right: T): [T, T] {
 return [left, right];
}
// ✅ valid: `T` meaningfully relates parameters and return type

ESLint flat config example​

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

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

When not to use it​

Disable this rule if your project intentionally keeps explicit, documentation-only type parameters even when they are not inferable or enforceable.

Package documentation​

Rule catalog ID: R031

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.