new Hono<{ Bindings: Env }>(); seems incompatible with Cloudflare wrangler generated type Env

[GregoryZeng]

Hi, I am starting to use Hono with Cloudflare Workers.
I find that const app = new Hono<{ Bindings: Env }>(); would raise TypeScript error:

Type '{ Bindings: Env; }' does not satisfy the constraint 'Env'.
  Types of property 'Bindings' are incompatible.
    Type 'Env' is not assignable to type 'Bindings'.
      Index signature for type 'string' is missing in type 'Env'.ts(2344)

where Env is a type for Cloudflare's related bindings. It is in ./worker-configuration.d.ts auto generated by command wrangler types:

interface Env {
	MY_VARIABLE: 'production_value';
	MY_BUCKET: R2Bucket;
	MY_DB: D1Database;
}

The TypeScript type inference works fine after I manually replace interface Env by type Env = . I am not expert in TypeScript typing and it is obviously not optimal.

Do you have any idea for this problem?

[yusukebe]

Hi @GregoryZeng

Do you have any idea for this problem?

Below are my ideas.

1. Don't use an interface. Use a type instead of it.
2. You can refer to the following code:

interface Env {
  MY_VARIABLE: 'production_value'
  MY_BUCKET: R2Bucket
  MY_DB: D1Database
}

type Bindings = {
  [key in keyof Env]: Env[key]
}

const app = new Hono<{ Bindings: Bindings }>()

[GregoryZeng]

Thanks! [key in keyof Env]: Env[key] is exactly what I need!