1 use if_chain::if_chain;
2 use rustc_errors::Applicability;
4 use rustc_hir::def::{DefKind, Res};
5 use rustc_hir::intravisit::{walk_item, walk_path, walk_ty, NestedVisitorMap, Visitor};
7 def, FnDecl, FnRetTy, FnSig, GenericArg, HirId, ImplItem, ImplItemKind, Item, ItemKind, Path, PathSegment, QPath,
10 use rustc_lint::{LateContext, LateLintPass, LintContext};
11 use rustc_middle::hir::map::Map;
12 use rustc_middle::lint::in_external_macro;
14 use rustc_middle::ty::{DefIdTree, Ty};
15 use rustc_session::{declare_lint_pass, declare_tool_lint};
16 use rustc_span::symbol::kw;
17 use rustc_typeck::hir_ty_to_ty;
19 use crate::utils::{differing_macro_contexts, span_lint_and_sugg};
21 declare_clippy_lint! {
22 /// **What it does:** Checks for unnecessary repetition of structure name when a
23 /// replacement with `Self` is applicable.
25 /// **Why is this bad?** Unnecessary repetition. Mixed use of `Self` and struct
27 /// feels inconsistent.
29 /// **Known problems:**
30 /// - False positive when using associated types (#2843)
31 /// - False positives in some situations when using generics (#3410)
46 /// fn new() -> Self {
53 "unnecessary structure name repetition whereas `Self` is applicable"
56 declare_lint_pass!(UseSelf => [USE_SELF]);
58 const SEGMENTS_MSG: &str = "segments should be composed of at least 1 element";
60 fn span_use_self_lint(cx: &LateContext<'_>, path: &Path<'_>, last_segment: Option<&PathSegment<'_>>) {
61 let last_segment = last_segment.unwrap_or_else(|| path.segments.last().expect(SEGMENTS_MSG));
63 // Path segments only include actual path, no methods or fields.
64 let last_path_span = last_segment.ident.span;
66 if differing_macro_contexts(path.span, last_path_span) {
70 // Only take path up to the end of last_path_span.
71 let span = path.span.with_hi(last_path_span.hi());
77 "unnecessary structure name repetition",
78 "use the applicable keyword",
80 Applicability::MachineApplicable,
84 // FIXME: always use this (more correct) visitor, not just in method signatures.
85 struct SemanticUseSelfVisitor<'a, 'tcx> {
86 cx: &'a LateContext<'tcx>,
90 impl<'a, 'tcx> Visitor<'tcx> for SemanticUseSelfVisitor<'a, 'tcx> {
93 fn visit_ty(&mut self, hir_ty: &'tcx hir::Ty<'_>) {
94 if let TyKind::Path(QPath::Resolved(_, path)) = &hir_ty.kind {
96 def::Res::SelfTy(..) => {},
98 if hir_ty_to_ty(self.cx.tcx, hir_ty) == self.self_ty {
99 span_use_self_lint(self.cx, path, None);
105 walk_ty(self, hir_ty)
108 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
109 NestedVisitorMap::None
113 fn check_trait_method_impl_decl<'tcx>(
114 cx: &LateContext<'tcx>,
115 impl_item: &ImplItem<'_>,
116 impl_decl: &'tcx FnDecl<'_>,
117 impl_trait_ref: ty::TraitRef<'tcx>,
119 let trait_method = cx
121 .associated_items(impl_trait_ref.def_id)
122 .find_by_name_and_kind(cx.tcx, impl_item.ident, ty::AssocKind::Fn, impl_trait_ref.def_id)
123 .expect("impl method matches a trait method");
125 let trait_method_sig = cx.tcx.fn_sig(trait_method.def_id);
126 let trait_method_sig = cx.tcx.erase_late_bound_regions(&trait_method_sig);
128 let output_hir_ty = if let FnRetTy::Return(ty) = &impl_decl.output {
134 // `impl_hir_ty` (of type `hir::Ty`) represents the type written in the signature.
135 // `trait_ty` (of type `ty::Ty`) is the semantic type for the signature in the trait.
136 // We use `impl_hir_ty` to see if the type was written as `Self`,
137 // `hir_ty_to_ty(...)` to check semantic types of paths, and
138 // `trait_ty` to determine which parts of the signature in the trait, mention
139 // the type being implemented verbatim (as opposed to `Self`).
140 for (impl_hir_ty, trait_ty) in impl_decl
143 .chain(output_hir_ty)
144 .zip(trait_method_sig.inputs_and_output)
146 // Check if the input/output type in the trait method specifies the implemented
147 // type verbatim, and only suggest `Self` if that isn't the case.
148 // This avoids suggestions to e.g. replace `Vec<u8>` with `Vec<Self>`,
149 // in an `impl Trait for u8`, when the trait always uses `Vec<u8>`.
150 // See also https://github.com/rust-lang/rust-clippy/issues/2894.
151 let self_ty = impl_trait_ref.self_ty();
152 if !trait_ty.walk().any(|inner| inner == self_ty.into()) {
153 let mut visitor = SemanticUseSelfVisitor { cx, self_ty };
155 visitor.visit_ty(&impl_hir_ty);
160 impl<'tcx> LateLintPass<'tcx> for UseSelf {
161 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
162 if in_external_macro(cx.sess(), item.span) {
166 if let ItemKind::Impl{ self_ty: ref item_type, items: refs, .. } = item.kind;
167 if let TyKind::Path(QPath::Resolved(_, ref item_path)) = item_type.kind;
169 let parameters = &item_path.segments.last().expect(SEGMENTS_MSG).args;
170 let should_check = parameters.as_ref().map_or(
172 |params| !params.parenthesized
173 &&!params.args.iter().any(|arg| matches!(arg, GenericArg::Lifetime(_)))
177 let visitor = &mut UseSelfVisitor {
181 let impl_def_id = cx.tcx.hir().local_def_id(item.hir_id);
182 let impl_trait_ref = cx.tcx.impl_trait_ref(impl_def_id);
184 if let Some(impl_trait_ref) = impl_trait_ref {
185 for impl_item_ref in refs {
186 let impl_item = cx.tcx.hir().impl_item(impl_item_ref.id);
187 if let ImplItemKind::Fn(FnSig{ decl: impl_decl, .. }, impl_body_id)
189 check_trait_method_impl_decl(cx, impl_item, impl_decl, impl_trait_ref);
191 let body = cx.tcx.hir().body(*impl_body_id);
192 visitor.visit_body(body);
194 visitor.visit_impl_item(impl_item);
198 for impl_item_ref in refs {
199 let impl_item = cx.tcx.hir().impl_item(impl_item_ref.id);
200 visitor.visit_impl_item(impl_item);
209 struct UseSelfVisitor<'a, 'tcx> {
210 item_path: &'a Path<'a>,
211 cx: &'a LateContext<'tcx>,
214 impl<'a, 'tcx> Visitor<'tcx> for UseSelfVisitor<'a, 'tcx> {
215 type Map = Map<'tcx>;
217 fn visit_path(&mut self, path: &'tcx Path<'_>, _id: HirId) {
218 if !path.segments.iter().any(|p| p.ident.span.is_dummy()) {
219 if path.segments.len() >= 2 {
220 let last_but_one = &path.segments[path.segments.len() - 2];
221 if last_but_one.ident.name != kw::SelfUpper {
222 let enum_def_id = match path.res {
223 Res::Def(DefKind::Variant, variant_def_id) => self.cx.tcx.parent(variant_def_id),
224 Res::Def(DefKind::Ctor(def::CtorOf::Variant, _), ctor_def_id) => {
225 let variant_def_id = self.cx.tcx.parent(ctor_def_id);
226 variant_def_id.and_then(|def_id| self.cx.tcx.parent(def_id))
231 if self.item_path.res.opt_def_id() == enum_def_id {
232 span_use_self_lint(self.cx, path, Some(last_but_one));
237 if path.segments.last().expect(SEGMENTS_MSG).ident.name != kw::SelfUpper {
238 if self.item_path.res == path.res {
239 span_use_self_lint(self.cx, path, None);
240 } else if let Res::Def(DefKind::Ctor(def::CtorOf::Struct, _), ctor_def_id) = path.res {
241 if self.item_path.res.opt_def_id() == self.cx.tcx.parent(ctor_def_id) {
242 span_use_self_lint(self.cx, path, None);
248 walk_path(self, path);
251 fn visit_item(&mut self, item: &'tcx Item<'_>) {
254 | ItemKind::Static(..)
256 | ItemKind::Struct(..)
257 | ItemKind::Union(..)
258 | ItemKind::Impl { .. }
259 | ItemKind::Fn(..) => {
260 // Don't check statements that shadow `Self` or where `Self` can't be used
262 _ => walk_item(self, item),
266 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
267 NestedVisitorMap::All(self.cx.tcx.hir())