While avoiding the TS error "Property 'request' does not exist on type 'EthereumProvider'" I encounter bug, "all declarations...identical modifiers"

Question

I am trying to supply types to TypeScript type checking. This is so that I can bypass Property 'request' does not exist on type 'EthereumProvider' like whats descriebd in the link below.

Specifically for window.ethereum I am trying to enable it by going:

import { MetaMaskInpageProvider } from "@metamask/providers";

// later...
declare global {
    interface Window {
        ethereum: MetaMaskInpageProvider;
        // ethereum: any;
    }
}

Like that.

But I get:

(property) Window.ethereum?: MetaMaskInpageProvider
All declarations of 'ethereum' must have identical modifiers.ts(2687)

This code is from here.

I don't understand "must have identical modifiers." What's that mean?

I don't have any other interfaces defining ethereum. So thats not it.

I also only reference "ethereum" in my code by going window.ethereum.doSomething

Any ideas?

Also I can't recreate this error because I have no idea how it came to be in the first place...

Answer 1

Solution was to throw in a ?

declare global {
    interface Window {
        ethereum?: MetaMaskInpageProvider; // note the ?
    }
}