typescript/no-duplicate-type-constituents Correctness

✅ This rule is turned on by default.

🚧 An auto-fix is still under development.

This rule disallows duplicate constituents of union or intersection types.

Duplicate constituents in union and intersection types serve no purpose and can make code harder to read. They are likely a mistake.

Examples of incorrect code for this rule:

type T1 = "A" | "A";

type T2 = A | A | B;

type T3 = { a: string } & { a: string };

type T4 = [A, A];

type T5 =
  | "foo"
  | "bar"
  | "foo";

Examples of correct code for this rule:

type T1 = "A" | "B";

type T2 = A | B | C;

type T3 = { a: string } & { b: string };

type T4 = [A, B];

type T5 =
  | "foo"
  | "bar"
  | "baz";

How to use

To enable this rule in the CLI or using the config file, you can use:

CLIConfig (.oxlintrc.json)

bash

oxlint --deny typescript/no-duplicate-type-constituents

json

{
  "rules": {
    "typescript/no-duplicate-type-constituents": "error"
  }
}