E0258: missing type between '|' and '|' (or '&' and '&')

An extra | or & is allowed at the beginning of a TypeScript type. However, it is a syntax error to write an extra | or & in the middle of a TypeScript type:

type Primitive =
  | string
  | number
  | bigint
  | boolean
  | null |
  | undefined

To fix this error, remove the extra | or &:

type Primitive =
  | string
  | number
  | bigint
  | boolean
  | null
  | undefined

Introduced in quick-lint-js version 2.7.0.

Documentation for other errors