clippy_utils/
paths.rs

1//! This module contains paths to types and functions Clippy needs to know
2//! about.
3//!
4//! Whenever possible, please consider diagnostic items over hardcoded paths.
5//! See <https://github.com/rust-lang/rust-clippy/issues/5393> for more information.
6
7use crate::res::MaybeQPath;
8use crate::sym;
9use rustc_ast::Mutability;
10use rustc_data_structures::fx::FxHashMap;
11use rustc_hir::def::Namespace::{MacroNS, TypeNS, ValueNS};
12use rustc_hir::def::{DefKind, Namespace, Res};
13use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId};
14use rustc_hir::{ItemKind, Node, UseKind};
15use rustc_lint::LateContext;
16use rustc_middle::ty::fast_reject::SimplifiedType;
17use rustc_middle::ty::layout::HasTyCtxt;
18use rustc_middle::ty::{FloatTy, IntTy, Ty, TyCtxt, UintTy};
19use rustc_span::{Ident, STDLIB_STABLE_CRATES, Symbol};
20use std::sync::OnceLock;
21
22/// Specifies whether to resolve a path in the [`TypeNS`], [`ValueNS`], [`MacroNS`] or in an
23/// arbitrary namespace
24#[derive(Clone, Copy, PartialEq, Debug)]
25pub enum PathNS {
26    Type,
27    Value,
28    Macro,
29
30    /// Resolves to the name in the first available namespace, e.g. for `std::vec` this would return
31    /// either the macro or the module but **not** both
32    ///
33    /// Must only be used when the specific resolution is unimportant such as in
34    /// `missing_enforced_import_renames`
35    Arbitrary,
36}
37
38impl PathNS {
39    fn matches(self, ns: Option<Namespace>) -> bool {
40        let required = match self {
41            PathNS::Type => TypeNS,
42            PathNS::Value => ValueNS,
43            PathNS::Macro => MacroNS,
44            PathNS::Arbitrary => return true,
45        };
46
47        ns == Some(required)
48    }
49}
50
51/// Lazily resolves a path into a list of [`DefId`]s using [`lookup_path`].
52///
53/// Typically it will contain one [`DefId`] or none, but in some situations there can be multiple:
54/// - `memchr::memchr` could return the functions from both memchr 1.0 and memchr 2.0
55/// - `alloc::boxed::Box::downcast` would return a function for each of the different inherent impls
56///   ([1], [2], [3])
57///
58/// [1]: https://doc.rust-lang.org/std/boxed/struct.Box.html#method.downcast
59/// [2]: https://doc.rust-lang.org/std/boxed/struct.Box.html#method.downcast-1
60/// [3]: https://doc.rust-lang.org/std/boxed/struct.Box.html#method.downcast-2
61pub struct PathLookup {
62    ns: PathNS,
63    path: &'static [Symbol],
64    once: OnceLock<Vec<DefId>>,
65}
66
67impl PathLookup {
68    /// Only exported for tests and `clippy_lints_internal`
69    #[doc(hidden)]
70    pub const fn new(ns: PathNS, path: &'static [Symbol]) -> Self {
71        Self {
72            ns,
73            path,
74            once: OnceLock::new(),
75        }
76    }
77
78    /// Returns the list of [`DefId`]s that the path resolves to
79    pub fn get<'tcx>(&self, tcx: &impl HasTyCtxt<'tcx>) -> &[DefId] {
80        self.once.get_or_init(|| lookup_path(tcx.tcx(), self.ns, self.path))
81    }
82
83    /// Returns the single [`DefId`] that the path resolves to, this can only be used for paths into
84    /// stdlib crates to avoid the issue of multiple [`DefId`]s being returned
85    ///
86    /// May return [`None`] in `no_std`/`no_core` environments
87    pub fn only(&self, cx: &LateContext<'_>) -> Option<DefId> {
88        let ids = self.get(cx);
89        debug_assert!(STDLIB_STABLE_CRATES.contains(&self.path[0]));
90        debug_assert!(ids.len() <= 1, "{ids:?}");
91        ids.first().copied()
92    }
93
94    /// Checks if the path resolves to the given `def_id`
95    pub fn matches<'tcx>(&self, tcx: &impl HasTyCtxt<'tcx>, def_id: DefId) -> bool {
96        self.get(&tcx.tcx()).contains(&def_id)
97    }
98
99    /// Resolves `maybe_path` to a [`DefId`] and checks if the [`PathLookup`] matches it
100    pub fn matches_path<'tcx>(&self, cx: &LateContext<'_>, maybe_path: impl MaybeQPath<'tcx>) -> bool {
101        maybe_path
102            .res(cx)
103            .opt_def_id()
104            .is_some_and(|def_id| self.matches(cx, def_id))
105    }
106
107    /// Checks if the path resolves to `ty`'s definition, must be an `Adt`
108    pub fn matches_ty<'tcx>(&self, tcx: &impl HasTyCtxt<'tcx>, ty: Ty<'_>) -> bool {
109        ty.ty_adt_def().is_some_and(|adt| self.matches(&tcx.tcx(), adt.did()))
110    }
111}
112
113macro_rules! path_macros {
114    ($($name:ident: $ns:expr,)*) => {
115        $(
116            /// Only exported for tests and `clippy_lints_internal`
117            #[doc(hidden)]
118            #[macro_export]
119            macro_rules! $name {
120                ($$($$seg:ident $$(::)?)*) => {
121                    PathLookup::new($ns, &[$$(sym::$$seg,)*])
122                };
123            }
124        )*
125    };
126}
127
128path_macros! {
129    type_path: PathNS::Type,
130    value_path: PathNS::Value,
131    macro_path: PathNS::Macro,
132}
133
134// Paths in external crates
135pub static FUTURES_IO_ASYNCREADEXT: PathLookup = type_path!(futures_util::AsyncReadExt);
136pub static FUTURES_IO_ASYNCWRITEEXT: PathLookup = type_path!(futures_util::AsyncWriteExt);
137pub static ITERTOOLS_NEXT_TUPLE: PathLookup = value_path!(itertools::Itertools::next_tuple);
138pub static PARKING_LOT_GUARDS: [PathLookup; 3] = [
139    type_path!(lock_api::mutex::MutexGuard),
140    type_path!(lock_api::rwlock::RwLockReadGuard),
141    type_path!(lock_api::rwlock::RwLockWriteGuard),
142];
143pub static REGEX_BUILDER_NEW: PathLookup = value_path!(regex::RegexBuilder::new);
144pub static REGEX_BYTES_BUILDER_NEW: PathLookup = value_path!(regex::bytes::RegexBuilder::new);
145pub static REGEX_BYTES_NEW: PathLookup = value_path!(regex::bytes::Regex::new);
146pub static REGEX_BYTES_SET_NEW: PathLookup = value_path!(regex::bytes::RegexSet::new);
147pub static REGEX_NEW: PathLookup = value_path!(regex::Regex::new);
148pub static REGEX_SET_NEW: PathLookup = value_path!(regex::RegexSet::new);
149pub static SERDE_DESERIALIZE: PathLookup = type_path!(serde::de::Deserialize);
150pub static SERDE_DE_VISITOR: PathLookup = type_path!(serde::de::Visitor);
151pub static TOKIO_FILE_OPTIONS: PathLookup = value_path!(tokio::fs::File::options);
152pub static TOKIO_IO_ASYNCREADEXT: PathLookup = type_path!(tokio::io::AsyncReadExt);
153pub static TOKIO_IO_ASYNCWRITEEXT: PathLookup = type_path!(tokio::io::AsyncWriteExt);
154pub static TOKIO_IO_OPEN_OPTIONS: PathLookup = type_path!(tokio::fs::OpenOptions);
155pub static TOKIO_IO_OPEN_OPTIONS_NEW: PathLookup = value_path!(tokio::fs::OpenOptions::new);
156pub static LAZY_STATIC: PathLookup = macro_path!(lazy_static::lazy_static);
157pub static ONCE_CELL_SYNC_LAZY: PathLookup = type_path!(once_cell::sync::Lazy);
158pub static ONCE_CELL_SYNC_LAZY_NEW: PathLookup = value_path!(once_cell::sync::Lazy::new);
159
160// Paths for internal lints go in `clippy_lints_internal/src/internal_paths.rs`
161
162/// Equivalent to a [`lookup_path`] after splitting the input string on `::`
163///
164/// This function is expensive and should be used sparingly.
165pub fn lookup_path_str(tcx: TyCtxt<'_>, ns: PathNS, path: &str) -> Vec<DefId> {
166    let path: Vec<Symbol> = path.split("::").map(Symbol::intern).collect();
167    lookup_path(tcx, ns, &path)
168}
169
170/// Resolves a def path like `std::vec::Vec`.
171///
172/// Typically it will return one [`DefId`] or none, but in some situations there can be multiple:
173/// - `memchr::memchr` could return the functions from both memchr 1.0 and memchr 2.0
174/// - `alloc::boxed::Box::downcast` would return a function for each of the different inherent impls
175///   ([1], [2], [3])
176///
177/// This function is expensive and should be used sparingly.
178///
179/// [1]: https://doc.rust-lang.org/std/boxed/struct.Box.html#method.downcast
180/// [2]: https://doc.rust-lang.org/std/boxed/struct.Box.html#method.downcast-1
181/// [3]: https://doc.rust-lang.org/std/boxed/struct.Box.html#method.downcast-2
182pub fn lookup_path(tcx: TyCtxt<'_>, ns: PathNS, path: &[Symbol]) -> Vec<DefId> {
183    let (root, rest) = match *path {
184        [] | [_] => return Vec::new(),
185        [root, ref rest @ ..] => (root, rest),
186    };
187
188    let mut out = Vec::new();
189    for &base in find_crates(tcx, root).iter().chain(find_primitive_impls(tcx, root)) {
190        lookup_with_base(tcx, base, ns, rest, &mut out);
191    }
192    out
193}
194
195/// Finds the crates called `name`, may be multiple due to multiple major versions.
196pub fn find_crates(tcx: TyCtxt<'_>, name: Symbol) -> &'static [DefId] {
197    static BY_NAME: OnceLock<FxHashMap<Symbol, Vec<DefId>>> = OnceLock::new();
198    let map = BY_NAME.get_or_init(|| {
199        let mut map = FxHashMap::default();
200        map.insert(tcx.crate_name(LOCAL_CRATE), vec![LOCAL_CRATE.as_def_id()]);
201        for &num in tcx.crates(()) {
202            map.entry(tcx.crate_name(num)).or_default().push(num.as_def_id());
203        }
204        map
205    });
206    match map.get(&name) {
207        Some(def_ids) => def_ids,
208        None => &[],
209    }
210}
211
212fn find_primitive_impls(tcx: TyCtxt<'_>, name: Symbol) -> &[DefId] {
213    let ty = match name {
214        sym::bool => SimplifiedType::Bool,
215        sym::char => SimplifiedType::Char,
216        sym::str => SimplifiedType::Str,
217        sym::array => SimplifiedType::Array,
218        sym::slice => SimplifiedType::Slice,
219        // FIXME: rustdoc documents these two using just `pointer`.
220        //
221        // Maybe this is something we should do here too.
222        sym::const_ptr => SimplifiedType::Ptr(Mutability::Not),
223        sym::mut_ptr => SimplifiedType::Ptr(Mutability::Mut),
224        sym::isize => SimplifiedType::Int(IntTy::Isize),
225        sym::i8 => SimplifiedType::Int(IntTy::I8),
226        sym::i16 => SimplifiedType::Int(IntTy::I16),
227        sym::i32 => SimplifiedType::Int(IntTy::I32),
228        sym::i64 => SimplifiedType::Int(IntTy::I64),
229        sym::i128 => SimplifiedType::Int(IntTy::I128),
230        sym::usize => SimplifiedType::Uint(UintTy::Usize),
231        sym::u8 => SimplifiedType::Uint(UintTy::U8),
232        sym::u16 => SimplifiedType::Uint(UintTy::U16),
233        sym::u32 => SimplifiedType::Uint(UintTy::U32),
234        sym::u64 => SimplifiedType::Uint(UintTy::U64),
235        sym::u128 => SimplifiedType::Uint(UintTy::U128),
236        sym::f32 => SimplifiedType::Float(FloatTy::F32),
237        sym::f64 => SimplifiedType::Float(FloatTy::F64),
238        _ => return &[],
239    };
240
241    tcx.incoherent_impls(ty)
242}
243
244/// Resolves a def path like `vec::Vec` with the base `std`.
245fn lookup_with_base(tcx: TyCtxt<'_>, mut base: DefId, ns: PathNS, mut path: &[Symbol], out: &mut Vec<DefId>) {
246    loop {
247        match *path {
248            [segment] => {
249                out.extend(item_child_by_name(tcx, base, ns, segment));
250
251                // When the current def_id is e.g. `struct S`, check the impl items in
252                // `impl S { ... }`
253                let inherent_impl_children = tcx
254                    .inherent_impls(base)
255                    .iter()
256                    .filter_map(|&impl_def_id| item_child_by_name(tcx, impl_def_id, ns, segment));
257                out.extend(inherent_impl_children);
258
259                return;
260            },
261            [segment, ref rest @ ..] => {
262                path = rest;
263                let Some(child) = item_child_by_name(tcx, base, PathNS::Type, segment) else {
264                    return;
265                };
266                base = child;
267            },
268            [] => unreachable!(),
269        }
270    }
271}
272
273fn item_child_by_name(tcx: TyCtxt<'_>, def_id: DefId, ns: PathNS, name: Symbol) -> Option<DefId> {
274    if let Some(local_id) = def_id.as_local() {
275        local_item_child_by_name(tcx, local_id, ns, name)
276    } else {
277        non_local_item_child_by_name(tcx, def_id, ns, name)
278    }
279}
280
281fn local_item_child_by_name(tcx: TyCtxt<'_>, local_id: LocalDefId, ns: PathNS, name: Symbol) -> Option<DefId> {
282    let root_mod;
283    let item_kind = match tcx.hir_node_by_def_id(local_id) {
284        Node::Crate(r#mod) => {
285            root_mod = ItemKind::Mod(Ident::dummy(), r#mod);
286            &root_mod
287        },
288        Node::Item(item) => &item.kind,
289        _ => return None,
290    };
291
292    match item_kind {
293        ItemKind::Mod(_, r#mod) => r#mod.item_ids.iter().find_map(|&item_id| {
294            let item = tcx.hir_item(item_id);
295            if let ItemKind::Use(path, UseKind::Single(ident)) = item.kind {
296                if ident.name == name {
297                    let opt_def_id = |ns: Option<Res>| ns.and_then(|res| res.opt_def_id());
298                    match ns {
299                        PathNS::Type => opt_def_id(path.res.type_ns),
300                        PathNS::Value => opt_def_id(path.res.value_ns),
301                        PathNS::Macro => opt_def_id(path.res.macro_ns),
302                        PathNS::Arbitrary => unreachable!(),
303                    }
304                } else {
305                    None
306                }
307            } else if let Some(ident) = item.kind.ident()
308                && ident.name == name
309                && ns.matches(tcx.def_kind(item.owner_id).ns())
310            {
311                Some(item.owner_id.to_def_id())
312            } else {
313                None
314            }
315        }),
316        ItemKind::Impl(..) | ItemKind::Trait(..) => tcx
317            .associated_items(local_id)
318            .filter_by_name_unhygienic(name)
319            .find(|assoc_item| ns.matches(Some(assoc_item.namespace())))
320            .map(|assoc_item| assoc_item.def_id),
321        _ => None,
322    }
323}
324
325fn non_local_item_child_by_name(tcx: TyCtxt<'_>, def_id: DefId, ns: PathNS, name: Symbol) -> Option<DefId> {
326    match tcx.def_kind(def_id) {
327        DefKind::Mod | DefKind::Enum | DefKind::Trait => tcx.module_children(def_id).iter().find_map(|child| {
328            if child.ident.name == name && ns.matches(child.res.ns()) {
329                child.res.opt_def_id()
330            } else {
331                None
332            }
333        }),
334        DefKind::Impl { .. } => tcx
335            .associated_item_def_ids(def_id)
336            .iter()
337            .copied()
338            .find(|assoc_def_id| tcx.item_name(*assoc_def_id) == name && ns.matches(tcx.def_kind(assoc_def_id).ns())),
339        _ => None,
340    }
341}
clippy_utils/paths.rs

clippy_utils/
paths.rs
