clippy_lints/src/use_self.rs

   1 use if_chain::if_chain;
   2 use rustc::hir::map::Map;
   3 use rustc::lint::in_external_macro;
   4 use rustc::ty;
   5 use rustc::ty::{DefIdTree, Ty};
   6 use rustc_errors::Applicability;
   7 use rustc_hir as hir;
   8 use rustc_hir::def::{DefKind, Res};
   9 use rustc_hir::intravisit::{walk_item, walk_path, walk_ty, NestedVisitorMap, Visitor};
  10 use rustc_hir::{
  11     def, FnDecl, FnRetTy, FnSig, GenericArg, HirId, ImplItem, ImplItemKind, Item, ItemKind, Path, PathSegment, QPath,
  12     TyKind,
  13 };
  14 use rustc_lint::{LateContext, LateLintPass, LintContext};
  15 use rustc_session::{declare_lint_pass, declare_tool_lint};
  16 use rustc_span::symbol::kw;
  17
  18 use crate::utils::{differing_macro_contexts, span_lint_and_sugg};
  19
  20 declare_clippy_lint! {
  21     /// **What it does:** Checks for unnecessary repetition of structure name when a
  22     /// replacement with `Self` is applicable.
  23     ///
  24     /// **Why is this bad?** Unnecessary repetition. Mixed use of `Self` and struct
  25     /// name
  26     /// feels inconsistent.
  27     ///
  28     /// **Known problems:**
  29     /// - False positive when using associated types (#2843)
  30     /// - False positives in some situations when using generics (#3410)
  31     ///
  32     /// **Example:**
  33     /// ```rust
  34     /// struct Foo {}
  35     /// impl Foo {
  36     ///     fn new() -> Foo {
  37     ///         Foo {}
  38     ///     }
  39     /// }
  40     /// ```
  41     /// could be
  42     /// ```rust
  43     /// struct Foo {}
  44     /// impl Foo {
  45     ///     fn new() -> Self {
  46     ///         Self {}
  47     ///     }
  48     /// }
  49     /// ```
  50     pub USE_SELF,
  51     nursery,
  52     "Unnecessary structure name repetition whereas `Self` is applicable"
  53 }
  54
  55 declare_lint_pass!(UseSelf => [USE_SELF]);
  56
  57 const SEGMENTS_MSG: &str = "segments should be composed of at least 1 element";
  58
  59 fn span_use_self_lint(cx: &LateContext<'_, '_>, path: &Path<'_>, last_segment: Option<&PathSegment<'_>>) {
  60     let last_segment = last_segment.unwrap_or_else(|| path.segments.last().expect(SEGMENTS_MSG));
  61
  62     // Path segments only include actual path, no methods or fields.
  63     let last_path_span = last_segment.ident.span;
  64
  65     if differing_macro_contexts(path.span, last_path_span) {
  66         return;
  67     }
  68
  69     // Only take path up to the end of last_path_span.
  70     let span = path.span.with_hi(last_path_span.hi());
  71
  72     span_lint_and_sugg(
  73         cx,
  74         USE_SELF,
  75         span,
  76         "unnecessary structure name repetition",
  77         "use the applicable keyword",
  78         "Self".to_owned(),
  79         Applicability::MachineApplicable,
  80     );
  81 }
  82
  83 struct TraitImplTyVisitor<'a, 'tcx> {
  84     item_type: Ty<'tcx>,
  85     cx: &'a LateContext<'a, 'tcx>,
  86     trait_type_walker: ty::walk::TypeWalker<'tcx>,
  87     impl_type_walker: ty::walk::TypeWalker<'tcx>,
  88 }
  89
  90 impl<'a, 'tcx> Visitor<'tcx> for TraitImplTyVisitor<'a, 'tcx> {
  91     type Map = Map<'tcx>;
  92
  93     fn visit_ty(&mut self, t: &'tcx hir::Ty<'_>) {
  94         let trait_ty = self.trait_type_walker.next();
  95         let impl_ty = self.impl_type_walker.next();
  96
  97         if_chain! {
  98             if let TyKind::Path(QPath::Resolved(_, path)) = &t.kind;
  99
 100             // The implementation and trait types don't match which means that
 101             // the concrete type was specified by the implementation
 102             if impl_ty != trait_ty;
 103             if let Some(impl_ty) = impl_ty;
 104             if self.item_type == impl_ty;
 105             then {
 106                 match path.res {
 107                     def::Res::SelfTy(..) => {},
 108                     _ => span_use_self_lint(self.cx, path, None)
 109                 }
 110             }
 111         }
 112
 113         walk_ty(self, t)
 114     }
 115
 116     fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
 117         NestedVisitorMap::None
 118     }
 119 }
 120
 121 fn check_trait_method_impl_decl<'a, 'tcx>(
 122     cx: &'a LateContext<'a, 'tcx>,
 123     item_type: Ty<'tcx>,
 124     impl_item: &ImplItem<'_>,
 125     impl_decl: &'tcx FnDecl<'_>,
 126     impl_trait_ref: &ty::TraitRef<'_>,
 127 ) {
 128     let trait_method = cx
 129         .tcx
 130         .associated_items(impl_trait_ref.def_id)
 131         .find_by_name_and_kind(cx.tcx, impl_item.ident, ty::AssocKind::Method, impl_trait_ref.def_id)
 132         .expect("impl method matches a trait method");
 133
 134     let trait_method_sig = cx.tcx.fn_sig(trait_method.def_id);
 135     let trait_method_sig = cx.tcx.erase_late_bound_regions(&trait_method_sig);
 136
 137     let impl_method_def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
 138     let impl_method_sig = cx.tcx.fn_sig(impl_method_def_id);
 139     let impl_method_sig = cx.tcx.erase_late_bound_regions(&impl_method_sig);
 140
 141     let output_ty = if let FnRetTy::Return(ty) = &impl_decl.output {
 142         Some(&**ty)
 143     } else {
 144         None
 145     };
 146
 147     // `impl_decl_ty` (of type `hir::Ty`) represents the type declared in the signature.
 148     // `impl_ty` (of type `ty:TyS`) is the concrete type that the compiler has determined for
 149     // that declaration. We use `impl_decl_ty` to see if the type was declared as `Self`
 150     // and use `impl_ty` to check its concrete type.
 151     for (impl_decl_ty, (impl_ty, trait_ty)) in impl_decl.inputs.iter().chain(output_ty).zip(
 152         impl_method_sig
 153             .inputs_and_output
 154             .iter()
 155             .zip(trait_method_sig.inputs_and_output),
 156     ) {
 157         let mut visitor = TraitImplTyVisitor {
 158             cx,
 159             item_type,
 160             trait_type_walker: trait_ty.walk(),
 161             impl_type_walker: impl_ty.walk(),
 162         };
 163
 164         visitor.visit_ty(&impl_decl_ty);
 165     }
 166 }
 167
 168 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UseSelf {
 169     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item<'_>) {
 170         if in_external_macro(cx.sess(), item.span) {
 171             return;
 172         }
 173         if_chain! {
 174             if let ItemKind::Impl{ self_ty: ref item_type, items: refs, .. } = item.kind;
 175             if let TyKind::Path(QPath::Resolved(_, ref item_path)) = item_type.kind;
 176             then {
 177                 let parameters = &item_path.segments.last().expect(SEGMENTS_MSG).args;
 178                 let should_check = if let Some(ref params) = *parameters {
 179                     !params.parenthesized && !params.args.iter().any(|arg| match arg {
 180                         GenericArg::Lifetime(_) => true,
 181                         _ => false,
 182                     })
 183                 } else {
 184                     true
 185                 };
 186
 187                 if should_check {
 188                     let visitor = &mut UseSelfVisitor {
 189                         item_path,
 190                         cx,
 191                     };
 192                     let impl_def_id = cx.tcx.hir().local_def_id(item.hir_id);
 193                     let impl_trait_ref = cx.tcx.impl_trait_ref(impl_def_id);
 194
 195                     if let Some(impl_trait_ref) = impl_trait_ref {
 196                         for impl_item_ref in refs {
 197                             let impl_item = cx.tcx.hir().impl_item(impl_item_ref.id);
 198                             if let ImplItemKind::Method(FnSig{ decl: impl_decl, .. }, impl_body_id)
 199                                     = &impl_item.kind {
 200                                 let item_type = cx.tcx.type_of(impl_def_id);
 201                                 check_trait_method_impl_decl(cx, item_type, impl_item, impl_decl, &impl_trait_ref);
 202
 203                                 let body = cx.tcx.hir().body(*impl_body_id);
 204                                 visitor.visit_body(body);
 205                             } else {
 206                                 visitor.visit_impl_item(impl_item);
 207                             }
 208                         }
 209                     } else {
 210                         for impl_item_ref in refs {
 211                             let impl_item = cx.tcx.hir().impl_item(impl_item_ref.id);
 212                             visitor.visit_impl_item(impl_item);
 213                         }
 214                     }
 215                 }
 216             }
 217         }
 218     }
 219 }
 220
 221 struct UseSelfVisitor<'a, 'tcx> {
 222     item_path: &'a Path<'a>,
 223     cx: &'a LateContext<'a, 'tcx>,
 224 }
 225
 226 impl<'a, 'tcx> Visitor<'tcx> for UseSelfVisitor<'a, 'tcx> {
 227     type Map = Map<'tcx>;
 228
 229     fn visit_path(&mut self, path: &'tcx Path<'_>, _id: HirId) {
 230         if !path.segments.iter().any(|p| p.ident.span.is_dummy()) {
 231             if path.segments.len() >= 2 {
 232                 let last_but_one = &path.segments[path.segments.len() - 2];
 233                 if last_but_one.ident.name != kw::SelfUpper {
 234                     let enum_def_id = match path.res {
 235                         Res::Def(DefKind::Variant, variant_def_id) => self.cx.tcx.parent(variant_def_id),
 236                         Res::Def(DefKind::Ctor(def::CtorOf::Variant, _), ctor_def_id) => {
 237                             let variant_def_id = self.cx.tcx.parent(ctor_def_id);
 238                             variant_def_id.and_then(|def_id| self.cx.tcx.parent(def_id))
 239                         },
 240                         _ => None,
 241                     };
 242
 243                     if self.item_path.res.opt_def_id() == enum_def_id {
 244                         span_use_self_lint(self.cx, path, Some(last_but_one));
 245                     }
 246                 }
 247             }
 248
 249             if path.segments.last().expect(SEGMENTS_MSG).ident.name != kw::SelfUpper {
 250                 if self.item_path.res == path.res {
 251                     span_use_self_lint(self.cx, path, None);
 252                 } else if let Res::Def(DefKind::Ctor(def::CtorOf::Struct, _), ctor_def_id) = path.res {
 253                     if self.item_path.res.opt_def_id() == self.cx.tcx.parent(ctor_def_id) {
 254                         span_use_self_lint(self.cx, path, None);
 255                     }
 256                 }
 257             }
 258         }
 259
 260         walk_path(self, path);
 261     }
 262
 263     fn visit_item(&mut self, item: &'tcx Item<'_>) {
 264         match item.kind {
 265             ItemKind::Use(..)
 266             | ItemKind::Static(..)
 267             | ItemKind::Enum(..)
 268             | ItemKind::Struct(..)
 269             | ItemKind::Union(..)
 270             | ItemKind::Impl { .. }
 271             | ItemKind::Fn(..) => {
 272                 // Don't check statements that shadow `Self` or where `Self` can't be used
 273             },
 274             _ => walk_item(self, item),
 275         }
 276     }
 277
 278     fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
 279         NestedVisitorMap::All(&self.cx.tcx.hir())
 280     }
 281 }