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, Path, QPath, TyKind,
14 use rustc_lint::{LateContext, LateLintPass, LintContext};
15 use rustc_middle::hir::map::Map;
16 use rustc_middle::ty::AssocKind;
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 {
79 types_to_skip: FxHashSet<HirId>,
84 impl_lint_pass!(UseSelf => [USE_SELF]);
86 const SEGMENTS_MSG: &str = "segments should be composed of at least 1 element";
88 impl<'tcx> LateLintPass<'tcx> for UseSelf {
89 fn check_item(&mut self, _cx: &LateContext<'_>, item: &Item<'_>) {
90 if matches!(item.kind, ItemKind::OpaqueTy(_)) {
91 // skip over `ItemKind::OpaqueTy` in order to lint `foo() -> impl <..>`
94 // We push the self types of `impl`s on a stack here. Only the top type on the stack is
95 // relevant for linting, since this is the self type of the `impl` we're currently in. To
96 // avoid linting on nested items, we push `StackItem::NoCheck` on the stack to signal, that
97 // we're in an `impl` or nested item, that we don't want to lint
98 let stack_item = if_chain! {
99 if let ItemKind::Impl(Impl { self_ty, .. }) = item.kind;
100 if let TyKind::Path(QPath::Resolved(_, item_path)) = self_ty.kind;
101 let parameters = &item_path.segments.last().expect(SEGMENTS_MSG).args;
102 if parameters.as_ref().map_or(true, |params| {
103 !params.parenthesized && !params.args.iter().any(|arg| matches!(arg, GenericArg::Lifetime(_)))
107 impl_id: item.def_id,
109 types_to_skip: std::iter::once(self_ty.hir_id).collect(),
115 self.stack.push(stack_item);
118 fn check_item_post(&mut self, _: &LateContext<'_>, item: &Item<'_>) {
119 if !matches!(item.kind, ItemKind::OpaqueTy(_)) {
124 fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
125 // We want to skip types in trait `impl`s that aren't declared as `Self` in the trait
126 // declaration. The collection of those types is all this method implementation does.
128 if let ImplItemKind::Fn(FnSig { decl, .. }, ..) = impl_item.kind;
129 if let Some(&mut StackItem::Check {
131 ref mut types_to_skip,
133 }) = self.stack.last_mut();
134 if let Some(impl_trait_ref) = cx.tcx.impl_trait_ref(impl_id);
136 // `self_ty` is the semantic self type of `impl <trait> for <type>`. This cannot be
138 let self_ty = impl_trait_ref.self_ty();
140 // `trait_method_sig` is the signature of the function, how it is declared in the
141 // trait, not in the impl of the trait.
142 let trait_method = cx
144 .associated_items(impl_trait_ref.def_id)
145 .find_by_name_and_kind(cx.tcx, impl_item.ident, AssocKind::Fn, impl_trait_ref.def_id)
146 .expect("impl method matches a trait method");
147 let trait_method_sig = cx.tcx.fn_sig(trait_method.def_id);
148 let trait_method_sig = cx.tcx.erase_late_bound_regions(trait_method_sig);
150 // `impl_inputs_outputs` is an iterator over the types (`hir::Ty`) declared in the
151 // implementation of the trait.
152 let output_hir_ty = if let FnRetTy::Return(ty) = &decl.output {
157 let impl_inputs_outputs = decl.inputs.iter().chain(output_hir_ty);
159 // `impl_hir_ty` (of type `hir::Ty`) represents the type written in the signature.
161 // `trait_sem_ty` (of type `ty::Ty`) is the semantic type for the signature in the
162 // trait declaration. This is used to check if `Self` was used in the trait
165 // If `any`where in the `trait_sem_ty` the `self_ty` was used verbatim (as opposed
166 // to `Self`), we want to skip linting that type and all subtypes of it. This
167 // avoids suggestions to e.g. replace `Vec<u8>` with `Vec<Self>`, in an `impl Trait
168 // for u8`, when the trait always uses `Vec<u8>`.
170 // See also https://github.com/rust-lang/rust-clippy/issues/2894.
171 for (impl_hir_ty, trait_sem_ty) in impl_inputs_outputs.zip(trait_method_sig.inputs_and_output) {
172 if trait_sem_ty.walk().any(|inner| inner == self_ty.into()) {
173 let mut visitor = SkipTyCollector::default();
174 visitor.visit_ty(impl_hir_ty);
175 types_to_skip.extend(visitor.types_to_skip);
182 fn check_body(&mut self, _: &LateContext<'_>, _: &hir::Body<'_>) {
183 // `hir_ty_to_ty` cannot be called in `Body`s or it will panic (sometimes). But in bodies
184 // we can use `cx.typeck_results.node_type(..)` to get the `ty::Ty` from a `hir::Ty`.
185 // However the `node_type()` method can *only* be called in bodies.
186 if let Some(&mut StackItem::Check { ref mut in_body, .. }) = self.stack.last_mut() {
187 *in_body = in_body.saturating_add(1);
191 fn check_body_post(&mut self, _: &LateContext<'_>, _: &hir::Body<'_>) {
192 if let Some(&mut StackItem::Check { ref mut in_body, .. }) = self.stack.last_mut() {
193 *in_body = in_body.saturating_sub(1);
197 fn check_ty(&mut self, cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>) {
199 if !in_macro(hir_ty.span);
200 if meets_msrv(self.msrv.as_ref(), &msrvs::TYPE_ALIAS_ENUM_VARIANTS);
201 if let Some(&StackItem::Check {
205 }) = self.stack.last();
206 if let TyKind::Path(QPath::Resolved(_, path)) = hir_ty.kind;
207 if !matches!(path.res, Res::SelfTy(..) | Res::Def(DefKind::TyParam, _));
208 if !types_to_skip.contains(&hir_ty.hir_id);
209 let ty = if in_body > 0 {
210 cx.typeck_results().node_type(hir_ty.hir_id)
212 hir_ty_to_ty(cx.tcx, hir_ty)
214 if same_type_and_consts(ty, cx.tcx.type_of(impl_id));
215 let hir = cx.tcx.hir();
216 let id = hir.get_parent_node(hir_ty.hir_id);
217 if !hir.opt_span(id).map_or(false, in_macro);
219 span_lint(cx, hir_ty.span);
224 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
226 if !in_macro(expr.span);
227 if meets_msrv(self.msrv.as_ref(), &msrvs::TYPE_ALIAS_ENUM_VARIANTS);
228 if let Some(&StackItem::Check { impl_id, .. }) = self.stack.last();
229 if cx.typeck_results().expr_ty(expr) == cx.tcx.type_of(impl_id);
230 then {} else { return; }
233 ExprKind::Struct(QPath::Resolved(_, path), ..) => match path.res {
234 Res::SelfTy(..) => (),
235 Res::Def(DefKind::Variant, _) => lint_path_to_variant(cx, path),
236 _ => span_lint(cx, path.span),
238 // tuple struct instantiation (`Foo(arg)` or `Enum::Foo(arg)`)
239 ExprKind::Call(fun, _) => {
240 if let ExprKind::Path(QPath::Resolved(_, path)) = fun.kind {
241 if let Res::Def(DefKind::Ctor(ctor_of, _), ..) = path.res {
243 CtorOf::Variant => lint_path_to_variant(cx, path),
244 CtorOf::Struct => span_lint(cx, path.span),
249 // unit enum variants (`Enum::A`)
250 ExprKind::Path(QPath::Resolved(_, path)) => lint_path_to_variant(cx, path),
255 extract_msrv_attr!(LateContext);
259 struct SkipTyCollector {
260 types_to_skip: Vec<HirId>,
263 impl<'tcx> Visitor<'tcx> for SkipTyCollector {
264 type Map = Map<'tcx>;
266 fn visit_ty(&mut self, hir_ty: &hir::Ty<'_>) {
267 self.types_to_skip.push(hir_ty.hir_id);
269 walk_ty(self, hir_ty);
272 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
273 NestedVisitorMap::None
277 fn span_lint(cx: &LateContext<'_>, span: Span) {
282 "unnecessary structure name repetition",
283 "use the applicable keyword",
285 Applicability::MachineApplicable,
289 fn lint_path_to_variant(cx: &LateContext<'_>, path: &Path<'_>) {
290 if let [.., self_seg, _variant] = path.segments {
293 .with_hi(self_seg.args().span_ext().unwrap_or(self_seg.ident.span).hi());