`needless_borrow`: do not contradict `dangerous_implicit_autorefs` (#14810)

Rust 1.88 introduces the `dangerous_implicit_autorefs` lint which warns
about using implicit autorefs on a place obtained from a raw pointer, as
this may create aliasing issues.

Prevent `clippy::needless_borrow` from triggering in this case, by
disabling the lint when taking a reference on a raw pointer dereference.
There might be a better way for doing this in the long run with a finer
way of distinguish the problematic cases, but this will prevent Clippy
from contradicting the compiler in the meantime.

Fixes rust-lang/rust-clippy#14743

changelog: [`needless_borrow`]: do not contradict the compiler's
`dangerous_implicit_autorefs` lint even though the refererences are not
mandatory

@rustbot label +beta-nominated

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### Summary Notes

- [Beta nomination for
1.88](https://github.com/rust-lang/rust-clippy/pull/14810#issuecomment-2883753957)
by [samueltardieu](https://github.com/samueltardieu)

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1 files changed, 9 insertions, 0 deletions

diff --git a/clippy_lints/src/dereference.rs b/clippy_lints/src/dereference.rs
index a22a2ee66d2..8045926b1de 100644
--- a/clippy_lints/src/dereference.rs
+++ b/clippy_lints/src/dereference.rs
@@ -986,6 +986,15 @@ fn report<'tcx>(
             );
         },
         State::DerefedBorrow(state) => {
+            // Do not suggest removing a non-mandatory `&` in `&*rawptr` in an `unsafe` context,
+            // as this may make rustc trigger its `dangerous_implicit_autorefs` lint.
+            if let ExprKind::AddrOf(BorrowKind::Ref, _, subexpr) = data.first_expr.kind
+                && let ExprKind::Unary(UnOp::Deref, subsubexpr) = subexpr.kind
+                && cx.typeck_results().expr_ty_adjusted(subsubexpr).is_raw_ptr()
+            {
+                return;
+            }
+
             let mut app = Applicability::MachineApplicable;
             let (snip, snip_is_macro) =
                 snippet_with_context(cx, expr.span, data.first_expr.span.ctxt(), "..", &mut app);