Prefer `readonly`/immutable types where possible | BeforeMerge Rules | BeforeMerge

Prefer `readonly`/immutable types where possible | BeforeMerge Rules | BeforeMerge

Why this matters

readonly documents intent and prevents accidental mutation of values that should be treated as immutable, especially shared config and props.

// Bad
interface Config { hosts: string[] }
function init(c: Config) { c.hosts.push("evil"); } // mutates caller's array
 
// Good
interface Config { readonly hosts: readonly string[] }
function init(c: Config) { c.hosts.push("x"); } // compile error