Check out this unique playground.
interface Feature {
readonly name: string;
}
// <Test>
// This is OK
interface Foo1 {
readonly arr: ReadonlyArray<Feature>;
}
function save1(foo: Foo1) {
console.log(foo);
}
// </Test>
// <Test>
// bad? why?
interface Foo2 {
arr: ReadonlyArray<Feature>;
}
function save2(foo: Foo2) {
console.log(foo);
}
// </Test>
// <Test>
// bad? why?
interface Foo3 {
readonly arr: Feature[];
}
function save3(foo: Foo3) {
console.log(foo);
}
// </Test>I believed that Foo1, Foo2, and Foo3 were identical, but according to
@typescript-eslint/prefer-readonly-parameter-typesFoo1consists of bothreadonlyandReadonlyArrayFoo2only containsReadonlyArrayFoo3solely hasreadonly
What sets these interfaces apart?