`if-let-rescope` migration with `cargo fix --edition` differs from documentation

[mitsuhiko]

This is tangentially related to #133167. I was looking for a way to opt out of that fix given the large number of false positives. A discussion in zulip pointed out that this lint as per documentation should not be enabled by default.

The if_let_rescope lint cannot deduce with complete confidence that the program semantics are preserved when the lifetime of such temporary values are shortened. For this reason, the suggestion from this lint is not automatically applied when running cargo fix --edition.

It is however definitely automatically applied. I'm not sure if this is a bug in the documentation or a bug in the implementation.

[ehuss]

Thanks for the report! This will be fixed by rust-lang/edition-guide#339. Closing since we don't track edition docs in this repo, and there is a PR up.