1 use crate::utils::{match_def_path, paths, span_lint, trait_ref_of_method};
3 use rustc_lint::{LateContext, LateLintPass};
4 use rustc_middle::ty::TypeFoldable;
5 use rustc_middle::ty::{Adt, Array, RawPtr, Ref, Slice, Tuple, Ty, TypeAndMut};
6 use rustc_session::{declare_lint_pass, declare_tool_lint};
7 use rustc_span::source_map::Span;
10 /// **What it does:** Checks for sets/maps with mutable key types.
12 /// **Why is this bad?** All of `HashMap`, `HashSet`, `BTreeMap` and
13 /// `BtreeSet` rely on either the hash or the order of keys be unchanging,
14 /// so having types with interior mutability is a bad idea.
16 /// **Known problems:** It's correct to use a struct, that contains interior mutability
17 /// as a key, when its `Hash` implementation doesn't access any of the interior mutable types.
18 /// However, this lint is unable to recognize this, so it causes a false positive in theses cases.
19 /// The `bytes` crate is a great example of this.
23 /// use std::cmp::{PartialEq, Eq};
24 /// use std::collections::HashSet;
25 /// use std::hash::{Hash, Hasher};
26 /// use std::sync::atomic::AtomicUsize;
29 /// struct Bad(AtomicUsize);
30 /// impl PartialEq for Bad {
31 /// fn eq(&self, rhs: &Self) -> bool {
33 /// ; unimplemented!();
37 /// impl Eq for Bad {}
39 /// impl Hash for Bad {
40 /// fn hash<H: Hasher>(&self, h: &mut H) {
42 /// ; unimplemented!();
47 /// let _: HashSet<Bad> = HashSet::new();
52 "Check for mutable `Map`/`Set` key type"
55 declare_lint_pass!(MutableKeyType => [ MUTABLE_KEY_TYPE ]);
57 impl<'tcx> LateLintPass<'tcx> for MutableKeyType {
58 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
59 if let hir::ItemKind::Fn(ref sig, ..) = item.kind {
60 check_sig(cx, item.hir_id, &sig.decl);
64 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::ImplItem<'tcx>) {
65 if let hir::ImplItemKind::Fn(ref sig, ..) = item.kind {
66 if trait_ref_of_method(cx, item.hir_id).is_none() {
67 check_sig(cx, item.hir_id, &sig.decl);
72 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::TraitItem<'tcx>) {
73 if let hir::TraitItemKind::Fn(ref sig, ..) = item.kind {
74 check_sig(cx, item.hir_id, &sig.decl);
78 fn check_local(&mut self, cx: &LateContext<'_>, local: &hir::Local<'_>) {
79 if let hir::PatKind::Wild = local.pat.kind {
82 check_ty(cx, local.span, cx.typeck_results().pat_ty(&*local.pat));
86 fn check_sig<'tcx>(cx: &LateContext<'tcx>, item_hir_id: hir::HirId, decl: &hir::FnDecl<'_>) {
87 let fn_def_id = cx.tcx.hir().local_def_id(item_hir_id);
88 let fn_sig = cx.tcx.fn_sig(fn_def_id);
89 for (hir_ty, ty) in decl.inputs.iter().zip(fn_sig.inputs().skip_binder().iter()) {
90 check_ty(cx, hir_ty.span, ty);
92 check_ty(cx, decl.output.span(), cx.tcx.erase_late_bound_regions(fn_sig.output()));
95 // We want to lint 1. sets or maps with 2. not immutable key types and 3. no unerased
96 // generics (because the compiler cannot ensure immutability for unknown types).
97 fn check_ty<'tcx>(cx: &LateContext<'tcx>, span: Span, ty: Ty<'tcx>) {
98 let ty = ty.peel_refs();
99 if let Adt(def, substs) = ty.kind() {
100 if [&paths::HASHMAP, &paths::BTREEMAP, &paths::HASHSET, &paths::BTREESET]
102 .any(|path| match_def_path(cx, def.did, &**path))
103 && is_mutable_type(cx, substs.type_at(0), span)
105 span_lint(cx, MUTABLE_KEY_TYPE, span, "mutable key type");
110 fn is_mutable_type<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, span: Span) -> bool {
112 RawPtr(TypeAndMut { ty: inner_ty, mutbl }) | Ref(_, inner_ty, mutbl) => {
113 mutbl == hir::Mutability::Mut || is_mutable_type(cx, inner_ty, span)
115 Slice(inner_ty) => is_mutable_type(cx, inner_ty, span),
116 Array(inner_ty, size) => {
117 size.try_eval_usize(cx.tcx, cx.param_env).map_or(true, |u| u != 0) && is_mutable_type(cx, inner_ty, span)
119 Tuple(..) => ty.tuple_fields().any(|ty| is_mutable_type(cx, ty, span)),
121 cx.tcx.layout_of(cx.param_env.and(ty)).is_ok()
122 && !ty.has_escaping_bound_vars()
123 && !ty.is_freeze(cx.tcx.at(span), cx.param_env)