<MockBackend as Backend>::Error should be a real error type

[a1phyr]

Currently, <MockBackend as Backend>::Error is () so it cannot be converted to Box<dyn std::error::Error>.

Using std::convert::Infallible or a standalone type that implement std::error::Error would be more convenient.

[tesselode]

Indeed. I came across this issue when trying to get the doc tests passing when the cpal feature isn't enabled. I ultimately didn't bother fixing it because there were other issues I would have to fix too, and it wasn't worth it. Are you finding this to be an issue outside of running tests?

[a1phyr]

I came across this issue in the exact same situation. I added "cpal" feature in my dev-dependencies and it worked.
It may still be worth fixing, though.

[tesselode]

Are you making a library based on Kira?

[a1phyr]

Yes I was making asset_manager-kira, an integration with assets_manager