Rust 1.99 will stabilize the never type and make Infallible an alias for it

Sources: LWN, HN discussion
Summary: The upcoming release stabilizes the never type and redefines Infallible as an alias for it. The accompanying fallback change breaks calls to generic functions that lack sufficient type information. Crater found 3,300 crates affected, seven of them fully broken, and backports fixed 1,553 ahead of the release.
Why it matters: A crate that relied on the old fallback needs an explicit type annotation to keep compiling, so the fix sits with library maintainers before the release rather than with users at upgrade time.