1 use clippy_utils::diagnostics::span_lint_and_then;
2 use clippy_utils::source::snippet;
3 use clippy_utils::ty::{implements_trait, is_copy};
4 use clippy_utils::{is_lint_allowed, match_def_path, paths};
5 use rustc_ast::ImplPolarity;
6 use rustc_hir::def_id::DefId;
7 use rustc_hir::{FieldDef, Item, ItemKind, Node};
8 use rustc_lint::{LateContext, LateLintPass};
9 use rustc_middle::lint::in_external_macro;
10 use rustc_middle::ty::{self, subst::GenericArgKind, Ty};
11 use rustc_session::{declare_tool_lint, impl_lint_pass};
14 declare_clippy_lint! {
16 /// Warns about fields in struct implementing `Send` that are neither `Send` nor `Copy`.
18 /// ### Why is this bad?
19 /// Sending the struct to another thread will transfer the ownership to
20 /// the new thread by dropping in the current thread during the transfer.
21 /// This causes soundness issues for non-`Send` fields, as they are also
22 /// dropped and might not be set up to handle this.
25 /// * [*The Rustonomicon* about *Send and Sync*](https://doc.rust-lang.org/nomicon/send-and-sync.html)
26 /// * [The documentation of `Send`](https://doc.rust-lang.org/std/marker/trait.Send.html)
28 /// ### Known Problems
29 /// Data structures that contain raw pointers may cause false positives.
30 /// They are sometimes safe to be sent across threads but do not implement
31 /// the `Send` trait. This lint has a heuristic to filter out basic cases
32 /// such as `Vec<*const T>`, but it's not perfect. Feel free to create an
33 /// issue if you have a suggestion on how this heuristic can be improved.
37 /// struct ExampleStruct<T> {
38 /// rc_is_not_send: Rc<String>,
39 /// unbounded_generic_field: T,
42 /// // This impl is unsound because it allows sending `!Send` types through `ExampleStruct`
43 /// unsafe impl<T> Send for ExampleStruct<T> {}
45 /// Use thread-safe types like [`std::sync::Arc`](https://doc.rust-lang.org/std/sync/struct.Arc.html)
46 /// or specify correct bounds on generic type parameters (`T: Send`).
47 #[clippy::version = "1.57.0"]
48 pub NON_SEND_FIELDS_IN_SEND_TY,
50 "there is field that does not implement `Send` in a `Send` struct"
53 #[derive(Copy, Clone)]
54 pub struct NonSendFieldInSendTy {
55 enable_raw_pointer_heuristic: bool,
58 impl NonSendFieldInSendTy {
59 pub fn new(enable_raw_pointer_heuristic: bool) -> Self {
61 enable_raw_pointer_heuristic,
66 impl_lint_pass!(NonSendFieldInSendTy => [NON_SEND_FIELDS_IN_SEND_TY]);
68 impl<'tcx> LateLintPass<'tcx> for NonSendFieldInSendTy {
69 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
70 let ty_allowed_in_send = if self.enable_raw_pointer_heuristic {
71 ty_allowed_with_raw_pointer_heuristic
73 ty_allowed_without_raw_pointer_heuristic
76 // Checks if we are in `Send` impl item.
77 // We start from `Send` impl instead of `check_field_def()` because
78 // single `AdtDef` may have multiple `Send` impls due to generic
79 // parameters, and the lint is much easier to implement in this way.
81 if !in_external_macro(cx.tcx.sess, item.span);
82 if let Some(send_trait) = cx.tcx.get_diagnostic_item(sym::Send);
83 if let ItemKind::Impl(hir_impl) = &item.kind;
84 if let Some(trait_ref) = &hir_impl.of_trait;
85 if let Some(trait_id) = trait_ref.trait_def_id();
86 if send_trait == trait_id;
87 if hir_impl.polarity == ImplPolarity::Positive;
88 if let Some(ty_trait_ref) = cx.tcx.impl_trait_ref(item.def_id);
89 if let self_ty = ty_trait_ref.self_ty();
90 if let ty::Adt(adt_def, impl_trait_substs) = self_ty.kind();
92 let mut non_send_fields = Vec::new();
94 let hir_map = cx.tcx.hir();
95 for variant in &adt_def.variants {
96 for field in &variant.fields {
98 if let Some(field_hir_id) = field
101 .map(|local_def_id| hir_map.local_def_id_to_hir_id(local_def_id));
102 if !is_lint_allowed(cx, NON_SEND_FIELDS_IN_SEND_TY, field_hir_id);
103 if let field_ty = field.ty(cx.tcx, impl_trait_substs);
104 if !ty_allowed_in_send(cx, field_ty, send_trait);
105 if let Node::Field(field_def) = hir_map.get(field_hir_id);
107 non_send_fields.push(NonSendField {
110 generic_params: collect_generic_params(cx, field_ty),
117 if !non_send_fields.is_empty() {
120 NON_SEND_FIELDS_IN_SEND_TY,
123 "this implementation is unsound, as some fields in `{}` are `!Send`",
124 snippet(cx, hir_impl.self_ty.span, "Unknown")
127 for field in non_send_fields {
130 &format!("the type of field `{}` is `!Send`", field.def.ident.name),
133 match field.generic_params.len() {
134 0 => diag.help("use a thread-safe type that implements `Send`"),
135 1 if is_ty_param(field.ty) => diag.help(&format!("add `{}: Send` bound in `Send` impl", field.ty)),
136 _ => diag.help(&format!(
137 "add bounds on type parameter{} `{}` that satisfy `{}: Send`",
138 if field.generic_params.len() > 1 { "s" } else { "" },
139 field.generic_params_string(),
140 snippet(cx, field.def.ty.span, "Unknown"),
152 struct NonSendField<'tcx> {
153 def: &'tcx FieldDef<'tcx>,
155 generic_params: Vec<Ty<'tcx>>,
158 impl<'tcx> NonSendField<'tcx> {
159 fn generic_params_string(&self) -> String {
162 .map(ToString::to_string)
168 /// Given a type, collect all of its generic parameters.
169 /// Example: `MyStruct<P, Box<Q, R>>` => `vec![P, Q, R]`
170 fn collect_generic_params<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Vec<Ty<'tcx>> {
172 .filter_map(|inner| match inner.unpack() {
173 GenericArgKind::Type(inner_ty) => Some(inner_ty),
176 .filter(|&inner_ty| is_ty_param(inner_ty))
180 /// Be more strict when the heuristic is disabled
181 fn ty_allowed_without_raw_pointer_heuristic<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, send_trait: DefId) -> bool {
182 if implements_trait(cx, ty, send_trait, &[]) {
186 if is_copy(cx, ty) && !contains_pointer_like(cx, ty) {
193 /// Heuristic to allow cases like `Vec<*const u8>`
194 fn ty_allowed_with_raw_pointer_heuristic<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, send_trait: DefId) -> bool {
195 if implements_trait(cx, ty, send_trait, &[]) || is_copy(cx, ty) {
199 // The type is known to be `!Send` and `!Copy`
203 .all(|ty| ty_allowed_with_raw_pointer_heuristic(cx, ty, send_trait)),
204 ty::Array(ty, _) | ty::Slice(ty) => ty_allowed_with_raw_pointer_heuristic(cx, ty, send_trait),
205 ty::Adt(_, substs) => {
206 if contains_pointer_like(cx, ty) {
207 // descends only if ADT contains any raw pointers
208 substs.iter().all(|generic_arg| match generic_arg.unpack() {
209 GenericArgKind::Type(ty) => ty_allowed_with_raw_pointer_heuristic(cx, ty, send_trait),
210 // Lifetimes and const generics are not solid part of ADT and ignored
211 GenericArgKind::Lifetime(_) | GenericArgKind::Const(_) => true,
217 // Raw pointers are `!Send` but allowed by the heuristic
218 ty::RawPtr(_) => true,
223 /// Checks if the type contains any pointer-like types in substs (including nested ones)
224 fn contains_pointer_like<'tcx>(cx: &LateContext<'tcx>, target_ty: Ty<'tcx>) -> bool {
225 for ty_node in target_ty.walk(cx.tcx) {
226 if let GenericArgKind::Type(inner_ty) = ty_node.unpack() {
227 match inner_ty.kind() {
231 ty::Adt(adt_def, _) => {
232 if match_def_path(cx, adt_def.did, &paths::PTR_NON_NULL) {
244 /// Returns `true` if the type is a type parameter such as `T`.
245 fn is_ty_param(target_ty: Ty<'_>) -> bool {
246 matches!(target_ty.kind(), ty::Param(_))