`clippy::unreachable`

Make the remaining case explicit or return an error; an unreachable! that is reached aborts the process.

What it reads

Clippy, with the compiler behind it. The only pass that compiles.

Ordinary defect.

The tier bounds how severe a rule may be; its category bounds the tier.

Turn it off, or make it blocking, without touching the code it flags:

rust-doctor --rule clippy::unreachable=off .
rust-doctor --rule clippy::unreachable=error .