1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use clippy_utils::ty::same_type_and_consts;
3 use clippy_utils::{in_macro, meets_msrv, msrvs};
4 use if_chain::if_chain;
5 use rustc_data_structures::fx::FxHashSet;
6 use rustc_errors::Applicability;
9 def::{CtorOf, DefKind, Res},
11 intravisit::{walk_ty, NestedVisitorMap, Visitor},
12 Expr, ExprKind, FnRetTy, FnSig, GenericArg, HirId, Impl, ImplItemKind, Item, ItemKind, Node, Path, QPath, TyKind,
14 use rustc_lint::{LateContext, LateLintPass, LintContext};
15 use rustc_middle::hir::map::Map;
16 use rustc_middle::ty::{AssocKind, Ty};
17 use rustc_semver::RustcVersion;
18 use rustc_session::{declare_tool_lint, impl_lint_pass};
20 use rustc_typeck::hir_ty_to_ty;
22 declare_clippy_lint! {
23 /// **What it does:** Checks for unnecessary repetition of structure name when a
24 /// replacement with `Self` is applicable.
26 /// **Why is this bad?** Unnecessary repetition. Mixed use of `Self` and struct
28 /// feels inconsistent.
30 /// **Known problems:**
31 /// - Unaddressed false negative in fn bodies of trait implementations
32 /// - False positive with assotiated types in traits (#4140)
48 /// fn new() -> Self {
55 "unnecessary structure name repetition whereas `Self` is applicable"
60 msrv: Option<RustcVersion>,
61 stack: Vec<StackItem>,
66 pub fn new(msrv: Option<RustcVersion>) -> Self {
78 impl_trait_ref_def_id: Option<LocalDefId>,
79 types_to_skip: FxHashSet<HirId>,
80 types_to_lint: Vec<HirId>,
85 impl_lint_pass!(UseSelf => [USE_SELF]);
87 const SEGMENTS_MSG: &str = "segments should be composed of at least 1 element";
89 impl<'tcx> LateLintPass<'tcx> for UseSelf {
90 fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
91 if !is_item_interesting(item) {
92 // This does two things:
93 // 1) Reduce needless churn on `self.stack`
94 // 2) Don't push `StackItem::NoCheck` when entering `ItemKind::OpaqueTy`,
95 // in order to lint `foo() -> impl <..>`
98 // We push the self types of `impl`s on a stack here. Only the top type on the stack is
99 // relevant for linting, since this is the self type of the `impl` we're currently in. To
100 // avoid linting on nested items, we push `StackItem::NoCheck` on the stack to signal, that
101 // we're in an `impl` or nested item, that we don't want to lint
102 let stack_item = if_chain! {
103 if let ItemKind::Impl(Impl { self_ty, ref of_trait, .. }) = item.kind;
104 if let TyKind::Path(QPath::Resolved(_, item_path)) = self_ty.kind;
105 let parameters = &item_path.segments.last().expect(SEGMENTS_MSG).args;
106 if parameters.as_ref().map_or(true, |params| {
107 !params.parenthesized && !params.args.iter().any(|arg| matches!(arg, GenericArg::Lifetime(_)))
110 let impl_trait_ref_def_id = of_trait.as_ref().map(|_| cx.tcx.hir().local_def_id(item.hir_id()));
112 hir_id: self_ty.hir_id,
113 impl_trait_ref_def_id,
114 types_to_lint: Vec::new(),
115 types_to_skip: std::iter::once(self_ty.hir_id).collect(),
121 self.stack.push(stack_item);
124 fn check_item_post(&mut self, _: &LateContext<'_>, item: &Item<'_>) {
125 if is_item_interesting(item) {
130 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
131 // We want to skip types in trait `impl`s that aren't declared as `Self` in the trait
132 // declaration. The collection of those types is all this method implementation does.
134 if let ImplItemKind::Fn(FnSig { decl, .. }, ..) = impl_item.kind;
135 if let Some(&mut StackItem::Check {
136 impl_trait_ref_def_id: Some(def_id),
137 ref mut types_to_skip,
139 }) = self.stack.last_mut();
140 if let Some(impl_trait_ref) = cx.tcx.impl_trait_ref(def_id);
142 // `self_ty` is the semantic self type of `impl <trait> for <type>`. This cannot be
144 let self_ty = impl_trait_ref.self_ty();
146 // `trait_method_sig` is the signature of the function, how it is declared in the
147 // trait, not in the impl of the trait.
148 let trait_method = cx
150 .associated_items(impl_trait_ref.def_id)
151 .find_by_name_and_kind(cx.tcx, impl_item.ident, AssocKind::Fn, impl_trait_ref.def_id)
152 .expect("impl method matches a trait method");
153 let trait_method_sig = cx.tcx.fn_sig(trait_method.def_id);
154 let trait_method_sig = cx.tcx.erase_late_bound_regions(trait_method_sig);
156 // `impl_inputs_outputs` is an iterator over the types (`hir::Ty`) declared in the
157 // implementation of the trait.
158 let output_hir_ty = if let FnRetTy::Return(ty) = &decl.output {
163 let impl_inputs_outputs = decl.inputs.iter().chain(output_hir_ty);
165 // `impl_hir_ty` (of type `hir::Ty`) represents the type written in the signature.
167 // `trait_sem_ty` (of type `ty::Ty`) is the semantic type for the signature in the
168 // trait declaration. This is used to check if `Self` was used in the trait
171 // If `any`where in the `trait_sem_ty` the `self_ty` was used verbatim (as opposed
172 // to `Self`), we want to skip linting that type and all subtypes of it. This
173 // avoids suggestions to e.g. replace `Vec<u8>` with `Vec<Self>`, in an `impl Trait
174 // for u8`, when the trait always uses `Vec<u8>`.
176 // See also https://github.com/rust-lang/rust-clippy/issues/2894.
177 for (impl_hir_ty, trait_sem_ty) in impl_inputs_outputs.zip(trait_method_sig.inputs_and_output) {
178 if trait_sem_ty.walk().any(|inner| inner == self_ty.into()) {
179 let mut visitor = SkipTyCollector::default();
180 visitor.visit_ty(impl_hir_ty);
181 types_to_skip.extend(visitor.types_to_skip);
188 fn check_body(&mut self, cx: &LateContext<'tcx>, body: &'tcx hir::Body<'_>) {
189 // `hir_ty_to_ty` cannot be called in `Body`s or it will panic (sometimes). But in bodies
190 // we can use `cx.typeck_results.node_type(..)` to get the `ty::Ty` from a `hir::Ty`.
191 // However the `node_type()` method can *only* be called in bodies.
193 // This method implementation determines which types should get linted in a `Body` and
194 // which shouldn't, with a visitor. We could directly lint in the visitor, but then we
195 // could only allow this lint on item scope. And we would have to check if those types are
196 // already dealt with in `check_ty` anyway.
197 if let Some(StackItem::Check {
202 }) = self.stack.last_mut()
204 let self_ty = ty_from_hir_id(cx, *hir_id);
206 let mut visitor = LintTyCollector {
209 types_to_lint: vec![],
210 types_to_skip: vec![],
212 visitor.visit_expr(&body.value);
213 types_to_lint.extend(visitor.types_to_lint);
214 types_to_skip.extend(visitor.types_to_skip);
218 fn check_ty(&mut self, cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>) {
220 if !in_macro(hir_ty.span);
221 if meets_msrv(self.msrv.as_ref(), &msrvs::TYPE_ALIAS_ENUM_VARIANTS);
222 if let Some(StackItem::Check {
227 }) = self.stack.last();
228 if !types_to_skip.contains(&hir_ty.hir_id);
229 if types_to_lint.contains(&hir_ty.hir_id)
231 let self_ty = ty_from_hir_id(cx, *hir_id);
232 should_lint_ty(hir_ty, hir_ty_to_ty(cx.tcx, hir_ty), self_ty)
234 let hir = cx.tcx.hir();
235 let id = hir.get_parent_node(hir_ty.hir_id);
236 if !hir.opt_span(id).map_or(false, in_macro);
238 span_lint(cx, hir_ty.span);
243 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
245 if !in_macro(expr.span);
246 if meets_msrv(self.msrv.as_ref(), &msrvs::TYPE_ALIAS_ENUM_VARIANTS);
247 if let Some(StackItem::Check { hir_id, .. }) = self.stack.last();
248 if cx.typeck_results().expr_ty(expr) == ty_from_hir_id(cx, *hir_id);
249 then {} else { return; }
252 ExprKind::Struct(QPath::Resolved(_, path), ..) => match path.res {
253 Res::SelfTy(..) => (),
254 Res::Def(DefKind::Variant, _) => lint_path_to_variant(cx, path),
255 _ => span_lint(cx, path.span),
257 // tuple struct instantiation (`Foo(arg)` or `Enum::Foo(arg)`)
258 ExprKind::Call(fun, _) => {
259 if let ExprKind::Path(QPath::Resolved(_, path)) = fun.kind {
260 if let Res::Def(DefKind::Ctor(ctor_of, _), ..) = path.res {
262 CtorOf::Variant => lint_path_to_variant(cx, path),
263 CtorOf::Struct => span_lint(cx, path.span),
268 // unit enum variants (`Enum::A`)
269 ExprKind::Path(QPath::Resolved(_, path)) => lint_path_to_variant(cx, path),
274 extract_msrv_attr!(LateContext);
278 struct SkipTyCollector {
279 types_to_skip: Vec<HirId>,
282 impl<'tcx> Visitor<'tcx> for SkipTyCollector {
283 type Map = Map<'tcx>;
285 fn visit_ty(&mut self, hir_ty: &hir::Ty<'_>) {
286 self.types_to_skip.push(hir_ty.hir_id);
288 walk_ty(self, hir_ty);
291 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
292 NestedVisitorMap::None
296 struct LintTyCollector<'a, 'tcx> {
297 cx: &'a LateContext<'tcx>,
299 types_to_lint: Vec<HirId>,
300 types_to_skip: Vec<HirId>,
303 impl<'a, 'tcx> Visitor<'tcx> for LintTyCollector<'a, 'tcx> {
304 type Map = Map<'tcx>;
306 fn visit_ty(&mut self, hir_ty: &'tcx hir::Ty<'_>) {
308 if let Some(ty) = self.cx.typeck_results().node_type_opt(hir_ty.hir_id);
309 if should_lint_ty(hir_ty, ty, self.self_ty);
311 self.types_to_lint.push(hir_ty.hir_id);
313 self.types_to_skip.push(hir_ty.hir_id);
317 walk_ty(self, hir_ty);
320 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
321 NestedVisitorMap::None
325 fn span_lint(cx: &LateContext<'_>, span: Span) {
330 "unnecessary structure name repetition",
331 "use the applicable keyword",
333 Applicability::MachineApplicable,
337 fn lint_path_to_variant(cx: &LateContext<'_>, path: &Path<'_>) {
338 if let [.., self_seg, _variant] = path.segments {
341 .with_hi(self_seg.args().span_ext().unwrap_or(self_seg.ident.span).hi());
346 fn is_item_interesting(item: &Item<'_>) -> bool {
347 use rustc_hir::ItemKind::{Const, Enum, Fn, Impl, Static, Struct, Trait, Union};
350 Impl { .. } | Static(..) | Const(..) | Fn(..) | Enum(..) | Struct(..) | Union(..) | Trait(..)
354 fn ty_from_hir_id<'tcx>(cx: &LateContext<'tcx>, hir_id: HirId) -> Ty<'tcx> {
355 if let Some(Node::Ty(hir_ty)) = cx.tcx.hir().find(hir_id) {
356 hir_ty_to_ty(cx.tcx, hir_ty)
358 unreachable!("This function should only be called with `HirId`s that are for sure `Node::Ty`")
362 fn should_lint_ty(hir_ty: &hir::Ty<'_>, ty: Ty<'_>, self_ty: Ty<'_>) -> bool {
364 if same_type_and_consts(ty, self_ty);
365 if let TyKind::Path(QPath::Resolved(_, path)) = hir_ty.kind;
367 !matches!(path.res, Res::SelfTy(..) | Res::Def(DefKind::TyParam, _))