Typescript directives reduce the effectiveness of the compiler, something which should only be done in exceptional circumstances. The reason why should be documented in a comment alongside the directive.

Invalid:

// @ts-expect-error
let a: number = "I am a string";

// @ts-ignore
let a: number = "I am a string";

// @ts-nocheck
let a: number = "I am a string";

Valid:

// @ts-expect-error: Temporary workaround (see ticket #422)
let a: number = "I am a string";

// @ts-ignore: Temporary workaround (see ticket #422)
let a: number = "I am a string";

// @ts-nocheck: Temporary workaround (see ticket #422)
let a: number = "I am a string";