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typescript/no-multi-type-tuples

Disallow union element types directly inside tuple elements.

Targeted pattern scope​

This rule targets union types used directly as tuple element types.

Example target shape: TSTupleType > TSUnionType.

What this rule reports​

This rule reports tuple elements written as unions (for example, [A | B]).

Why this rule exists​

Extracting tuple union elements into named aliases can improve readability and reuse.

❌ Incorrect​

type T = [string | number];

✅ Correct​

type Value = string | number;
type T = [Value];

Behavior and migration notes​

This rule reports only and does not provide an autofix.

Migration is usually introducing a named alias for the union and using that alias in the tuple.

Options​

This rule has no options.

Additional examples​

type Pair = [string | number, boolean];
// ❌ reported on `string | number`

type Value = string | number;
type PairFixed = [Value, boolean];
// ✅ valid

ESLint flat config example​

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

export default [
 {
  plugins: { "etc-misc": etcMisc },
  rules: {
   "etc-misc/typescript/no-multi-type-tuples": "error",
  },
 },
];

When not to use it​

Disable this rule if inline union tuple element types are preferred in your project.

Package documentation​

Rule catalog ID: R090

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.