1 use clippy_utils::diagnostics::span_lint;
2 use clippy_utils::trait_ref_of_method;
4 use rustc_lint::{LateContext, LateLintPass};
5 use rustc_middle::ty::TypeFoldable;
6 use rustc_middle::ty::{Adt, Array, RawPtr, Ref, Slice, Tuple, Ty, TypeAndMut};
7 use rustc_session::{declare_lint_pass, declare_tool_lint};
8 use rustc_span::source_map::Span;
9 use rustc_span::symbol::sym;
12 declare_clippy_lint! {
14 /// Checks for sets/maps with mutable key types.
16 /// ### Why is this bad?
17 /// All of `HashMap`, `HashSet`, `BTreeMap` and
18 /// `BtreeSet` rely on either the hash or the order of keys be unchanging,
19 /// so having types with interior mutability is a bad idea.
21 /// ### Known problems
22 /// It's correct to use a struct, that contains interior mutability
23 /// as a key, when its `Hash` implementation doesn't access any of the interior mutable types.
24 /// However, this lint is unable to recognize this, so it causes a false positive in theses cases.
25 /// The `bytes` crate is a great example of this.
29 /// use std::cmp::{PartialEq, Eq};
30 /// use std::collections::HashSet;
31 /// use std::hash::{Hash, Hasher};
32 /// use std::sync::atomic::AtomicUsize;
35 /// struct Bad(AtomicUsize);
36 /// impl PartialEq for Bad {
37 /// fn eq(&self, rhs: &Self) -> bool {
39 /// ; unimplemented!();
43 /// impl Eq for Bad {}
45 /// impl Hash for Bad {
46 /// fn hash<H: Hasher>(&self, h: &mut H) {
48 /// ; unimplemented!();
53 /// let _: HashSet<Bad> = HashSet::new();
58 "Check for mutable `Map`/`Set` key type"
61 declare_lint_pass!(MutableKeyType => [ MUTABLE_KEY_TYPE ]);
63 impl<'tcx> LateLintPass<'tcx> for MutableKeyType {
64 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
65 if let hir::ItemKind::Fn(ref sig, ..) = item.kind {
66 check_sig(cx, item.hir_id(), sig.decl);
70 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::ImplItem<'tcx>) {
71 if let hir::ImplItemKind::Fn(ref sig, ..) = item.kind {
72 if trait_ref_of_method(cx, item.hir_id()).is_none() {
73 check_sig(cx, item.hir_id(), sig.decl);
78 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::TraitItem<'tcx>) {
79 if let hir::TraitItemKind::Fn(ref sig, ..) = item.kind {
80 check_sig(cx, item.hir_id(), sig.decl);
84 fn check_local(&mut self, cx: &LateContext<'_>, local: &hir::Local<'_>) {
85 if let hir::PatKind::Wild = local.pat.kind {
88 check_ty(cx, local.span, cx.typeck_results().pat_ty(&*local.pat));
92 fn check_sig<'tcx>(cx: &LateContext<'tcx>, item_hir_id: hir::HirId, decl: &hir::FnDecl<'_>) {
93 let fn_def_id = cx.tcx.hir().local_def_id(item_hir_id);
94 let fn_sig = cx.tcx.fn_sig(fn_def_id);
95 for (hir_ty, ty) in iter::zip(decl.inputs, fn_sig.inputs().skip_binder()) {
96 check_ty(cx, hir_ty.span, ty);
98 check_ty(cx, decl.output.span(), cx.tcx.erase_late_bound_regions(fn_sig.output()));
101 // We want to lint 1. sets or maps with 2. not immutable key types and 3. no unerased
102 // generics (because the compiler cannot ensure immutability for unknown types).
103 fn check_ty<'tcx>(cx: &LateContext<'tcx>, span: Span, ty: Ty<'tcx>) {
104 let ty = ty.peel_refs();
105 if let Adt(def, substs) = ty.kind() {
106 if [sym::hashmap_type, sym::BTreeMap, sym::hashset_type, sym::BTreeMap]
108 .any(|diag_item| cx.tcx.is_diagnostic_item(*diag_item, def.did))
109 && is_mutable_type(cx, substs.type_at(0), span)
111 span_lint(cx, MUTABLE_KEY_TYPE, span, "mutable key type");
116 fn is_mutable_type<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, span: Span) -> bool {
118 RawPtr(TypeAndMut { ty: inner_ty, mutbl }) | Ref(_, inner_ty, mutbl) => {
119 mutbl == hir::Mutability::Mut || is_mutable_type(cx, inner_ty, span)
121 Slice(inner_ty) => is_mutable_type(cx, inner_ty, span),
122 Array(inner_ty, size) => {
123 size.try_eval_usize(cx.tcx, cx.param_env).map_or(true, |u| u != 0) && is_mutable_type(cx, inner_ty, span)
125 Tuple(..) => ty.tuple_fields().any(|ty| is_mutable_type(cx, ty, span)),
127 !ty.has_escaping_bound_vars()
128 && cx.tcx.layout_of(cx.param_env.and(ty)).is_ok()
129 && !ty.is_freeze(cx.tcx.at(span), cx.param_env)