diff --git a/clippy_lints/src/matches/significant_drop_in_scrutinee.rs b/clippy_lints/src/matches/significant_drop_in_scrutinee.rs index 10c3203725a8..3171acda4423 100644 --- a/clippy_lints/src/matches/significant_drop_in_scrutinee.rs +++ b/clippy_lints/src/matches/significant_drop_in_scrutinee.rs @@ -115,45 +115,60 @@ impl<'a, 'tcx> SigDropChecker<'a, 'tcx> { } } - fn get_type(&self, ex: &'tcx Expr<'_>) -> Ty<'tcx> { - self.cx.typeck_results().expr_ty(ex) + fn is_sig_drop_expr(&mut self, ex: &'tcx Expr<'_>) -> bool { + !ex.is_syntactic_place_expr() && self.has_sig_drop_attr(self.cx.typeck_results().expr_ty(ex)) } - fn has_seen_type(&mut self, ty: Ty<'tcx>) -> bool { - !self.seen_types.insert(ty) + fn has_sig_drop_attr(&mut self, ty: Ty<'tcx>) -> bool { + self.seen_types.clear(); + self.has_sig_drop_attr_impl(ty) } - fn has_sig_drop_attr(&mut self, cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool { + fn has_sig_drop_attr_impl(&mut self, ty: Ty<'tcx>) -> bool { if let Some(adt) = ty.ty_adt_def() { - if get_attr(cx.sess(), cx.tcx.get_attrs_unchecked(adt.did()), "has_significant_drop").count() > 0 { + if get_attr( + self.cx.sess(), + self.cx.tcx.get_attrs_unchecked(adt.did()), + "has_significant_drop", + ) + .count() + > 0 + { return true; } } - match ty.kind() { - rustc_middle::ty::Adt(a, b) => { - for f in a.all_fields() { - let ty = f.ty(cx.tcx, b); - if !self.has_seen_type(ty) && self.has_sig_drop_attr(cx, ty) { - return true; - } - } + if !self.seen_types.insert(ty) { + return false; + } - for generic_arg in *b { - if let GenericArgKind::Type(ty) = generic_arg.unpack() { - if self.has_sig_drop_attr(cx, ty) { - return true; - } - } - } - false + let result = match ty.kind() { + rustc_middle::ty::Adt(adt, args) => { + // if some field has significant drop, + adt.all_fields() + .map(|field| field.ty(self.cx.tcx, args)) + .any(|ty| self.has_sig_drop_attr_impl(ty)) + // or if there is no generic lifetime and.. + // (to avoid false positive on `Ref<'a, MutexGuard>`) + || (args + .iter() + .all(|arg| !matches!(arg.unpack(), GenericArgKind::Lifetime(_))) + // some generic parameter has significant drop + // (to avoid false negative on `Box>`) + && args + .iter() + .filter_map(|arg| match arg.unpack() { + GenericArgKind::Type(ty) => Some(ty), + _ => None, + }) + .any(|ty| self.has_sig_drop_attr_impl(ty))) }, - rustc_middle::ty::Array(ty, _) - | rustc_middle::ty::RawPtr(ty, _) - | rustc_middle::ty::Ref(_, ty, _) - | rustc_middle::ty::Slice(ty) => self.has_sig_drop_attr(cx, *ty), + rustc_middle::ty::Tuple(tys) => tys.iter().any(|ty| self.has_sig_drop_attr_impl(ty)), + rustc_middle::ty::Array(ty, _) | rustc_middle::ty::Slice(ty) => self.has_sig_drop_attr_impl(*ty), _ => false, - } + }; + + result } } @@ -232,7 +247,7 @@ impl<'a, 'tcx> SigDropHelper<'a, 'tcx> { if self.current_sig_drop.is_some() { return; } - let ty = self.sig_drop_checker.get_type(expr); + let ty = self.cx.typeck_results().expr_ty(expr); if ty.is_ref() { // We checked that the type was ref, so builtin_deref will return Some TypeAndMut, // but let's avoid any chance of an ICE @@ -279,11 +294,7 @@ impl<'a, 'tcx> SigDropHelper<'a, 'tcx> { impl<'a, 'tcx> Visitor<'tcx> for SigDropHelper<'a, 'tcx> { fn visit_expr(&mut self, ex: &'tcx Expr<'_>) { - if !self.is_chain_end - && self - .sig_drop_checker - .has_sig_drop_attr(self.cx, self.sig_drop_checker.get_type(ex)) - { + if !self.is_chain_end && self.sig_drop_checker.is_sig_drop_expr(ex) { self.has_significant_drop = true; return; } @@ -387,10 +398,7 @@ fn has_significant_drop_in_arms<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<' impl<'a, 'tcx> Visitor<'tcx> for ArmSigDropHelper<'a, 'tcx> { fn visit_expr(&mut self, ex: &'tcx Expr<'tcx>) { - if self - .sig_drop_checker - .has_sig_drop_attr(self.sig_drop_checker.cx, self.sig_drop_checker.get_type(ex)) - { + if self.sig_drop_checker.is_sig_drop_expr(ex) { self.found_sig_drop_spans.insert(ex.span); return; } diff --git a/tests/ui/significant_drop_in_scrutinee.rs b/tests/ui/significant_drop_in_scrutinee.rs index 0305d895fc58..7fc89bb95380 100644 --- a/tests/ui/significant_drop_in_scrutinee.rs +++ b/tests/ui/significant_drop_in_scrutinee.rs @@ -675,4 +675,60 @@ fn should_not_trigger_on_significant_iterator_drop() { } } +// https://github.com/rust-lang/rust-clippy/issues/9072 +fn should_not_trigger_lint_if_place_expr_has_significant_drop() { + let x = Mutex::new(vec![1, 2, 3]); + let x_guard = x.lock().unwrap(); + + match x_guard[0] { + 1 => println!("1!"), + x => println!("{x}"), + } + + match x_guard.len() { + 1 => println!("1!"), + x => println!("{x}"), + } +} + +struct Guard<'a, T>(MutexGuard<'a, T>); + +struct Ref<'a, T>(&'a T); + +impl<'a, T> Guard<'a, T> { + fn guard(&self) -> &MutexGuard { + &self.0 + } + + fn guard_ref(&self) -> Ref> { + Ref(&self.0) + } + + fn take(self) -> Box> { + Box::new(self.0) + } +} + +fn should_not_trigger_for_significant_drop_ref() { + let mutex = Mutex::new(vec![1, 2]); + let guard = Guard(mutex.lock().unwrap()); + + match guard.guard().len() { + 0 => println!("empty"), + _ => println!("not empty"), + } + + match guard.guard_ref().0.len() { + 0 => println!("empty"), + _ => println!("not empty"), + } + + match guard.take().len() { + //~^ ERROR: temporary with significant `Drop` in `match` scrutinee will live until the + //~| NOTE: this might lead to deadlocks or other unexpected behavior + 0 => println!("empty"), + _ => println!("not empty"), + }; +} + fn main() {} diff --git a/tests/ui/significant_drop_in_scrutinee.stderr b/tests/ui/significant_drop_in_scrutinee.stderr index 7d5b1acc7f00..811bb0655279 100644 --- a/tests/ui/significant_drop_in_scrutinee.stderr +++ b/tests/ui/significant_drop_in_scrutinee.stderr @@ -28,6 +28,9 @@ LL | match s.lock_m().get_the_value() { LL | println!("{}", s.lock_m().get_the_value()); | ---------- another value with significant `Drop` created here ... +LL | println!("{}", s.lock_m().get_the_value()); + | ---------- another value with significant `Drop` created here +... LL | } | - temporary lives until here | @@ -47,6 +50,9 @@ LL | match s.lock_m_m().get_the_value() { LL | println!("{}", s.lock_m().get_the_value()); | ---------- another value with significant `Drop` created here ... +LL | println!("{}", s.lock_m().get_the_value()); + | ---------- another value with significant `Drop` created here +... LL | } | - temporary lives until here | @@ -360,7 +366,7 @@ LL | match s.lock().deref().deref() { | ^^^^^^^^^^^^^^^^^^^^^^^^ ... LL | _ => println!("Value is {}", s.lock().deref()), - | ---------------- another value with significant `Drop` created here + | -------- another value with significant `Drop` created here LL | }; | - temporary lives until here | @@ -378,7 +384,7 @@ LL | match s.lock().deref().deref() { | ^^^^^^^^^^^^^^^^^^^^^^^^ ... LL | matcher => println!("Value is {}", s.lock().deref()), - | ---------------- another value with significant `Drop` created here + | -------- another value with significant `Drop` created here LL | _ => println!("Value was not a match"), LL | }; | - temporary lives until here @@ -499,5 +505,21 @@ LL ~ let value = mutex.lock().unwrap().foo(); LL ~ match value { | -error: aborting due to 26 previous errors +error: temporary with significant `Drop` in `match` scrutinee will live until the end of the `match` expression + --> tests/ui/significant_drop_in_scrutinee.rs:726:11 + | +LL | match guard.take().len() { + | ^^^^^^^^^^^^^^^^^^ +... +LL | }; + | - temporary lives until here + | + = note: this might lead to deadlocks or other unexpected behavior +help: try moving the temporary above the match + | +LL ~ let value = guard.take().len(); +LL ~ match value { + | + +error: aborting due to 27 previous errors