This POC shows a simple example on how an Env type could be defined in the @cloudflare/workers-types package and extended/used externally (one of the main use cases being getPlatformProxy).
In src/index.ts you can see the Env type being expanded:
declare module '@cloudflare/workers-types/base' {
interface Env {
MY_VAR: number;
}
}Such expansion could be also implemented opt-in by wrangler types.
As I mentioned one of the biggest benefits of this would be the possible customization of the Env interface externally in combination with getPlatformProxy.
For example frameworks/libraries using getPlatformProxy could, without any change on their part, allow developers to customize their Env type (similarly to this example).
Related discussion: pi0/nitro-cloudflare-dev#13