Move coerce_container_to_any to suspicious

[Ralith]

changelog: [coerce_container_to_any]: move from nursery to suspicious

Motivated by organic demand on bsky.

[rustbot]

r? @dswij

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• Owners of files modified in this PR: 7 candidates
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• Random selection from Jarcho, dswij, llogiq, samueltardieu

[samueltardieu]

I would prefer to see more tests before this lint becomes warning-by-default. In particular, tests where part of the expression comes from macros, or embedded inside macro, etc., to make sure that the suggested fix can always be applied.

For example, the following code will trigger the lint while it should probably not:

    macro_rules! mac {
        ($n:ident, $e:expr) => { let $n: &dyn Any = $e; };
    }
    let x: Box<dyn Any> = Box::new(());
    mac!(ref_x, &x);

[Ralith]

Shouldn't it? If I saw such code in the wild I'd strongly expect the intended syntax to be mac!(ref_x, &*x), exactly per the lint.

[samueltardieu]

If the macro is external, having a message such as "error: coercing &std::boxed::Box<dyn std::any::Any> to &dyn Any" is a bit strange, as the macro is supposedly "opaque" (for example if it's a proc-macro).