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Auto merge of #10864 - y21:issue10437, r=blyxyas,xFrednet

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[`unnecessary_lazy_eval`]: don't lint on types with deref impl

Fixes #10437.
This PR changes clippy's util module `eager_or_lazy` to also consider deref expressions whose type has a non-builtin deref impl and not suggest replacing it as that might have observable side effects.
A prominent example might be the `lazy_static` macro, which creates a newtype with a `Deref` impl that you need to go through to get access to the inner value. Going from lazy to eager can make a difference there.

changelog: [`unnecessary_lazy_eval`]: don't lint on types with non-builtin deref impl
This commit is contained in:
bors 2023-06-05 11:21:45 +00:00
commit b033883e2b
4 changed files with 97 additions and 37 deletions
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8
clippy_utils/src/eager_or_lazy.rs
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@ -173,11 +173,15 @@ fn expr_eagerness<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> EagernessS
self.eagerness = Lazy;
}
},
// Custom `Deref` impl might have side effects
ExprKind::Unary(UnOp::Deref, e)
if self.cx.typeck_results().expr_ty(e).builtin_deref(true).is_none() =>
{
self.eagerness |= NoChange;
},
// Dereferences should be cheap, but dereferencing a raw pointer earlier may not be safe.
ExprKind::Unary(UnOp::Deref, e) if !self.cx.typeck_results().expr_ty(e).is_unsafe_ptr() => (),
ExprKind::Unary(UnOp::Deref, _) => self.eagerness |= NoChange,
ExprKind::Unary(_, e)
if matches!(
self.cx.typeck_results().expr_ty(e).kind(),