Fix clippy::ref_as_ptr for non-temporary references in let/const

[Abd002]

Fix ref_as_ptr false positives for temporary values and let/static/const initializers.

Fixes #16220

changelog: [ref_as_ptr]: Only lint on non-temporary expressions)

[rustbot]

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[rustbot]

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[samueltardieu]

Thanks for your contribution.

Could you either link to an issue describing the problem (or open one, and marked it closed by this pull-request), or make sure you describe it (and include tests that failed before) in the commit description?

[github-actions]

No changes for aefb01b

[Abd002]

Done

[Jarcho]

You have the wrong conditions here. This can't lint if the cast is in a context that supports lifetime extension and the casted expression is a borrow of a temporary. All other cases are ok to lint.

[Jarcho]

You're missing tests for additional things that should lint now. e.g.

let _ = &x as *const _;
let _ = &*x as *const _;
let _ = &x.0 as *const _;

[Abd002]

You're missing tests for additional things that should lint now. e.g.

let _ = &x as *const _;
let _ = &*x as *const _;
let _ = &x.0 as *const _;

Tests are included

[Jarcho]

Thank you.

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