clippy_lints/src/use_self.rs

   1 use if_chain::if_chain;
   2 use rustc::declare_lint_pass;
   3 use rustc::hir::map::Map;
   4 use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
   5 use rustc::ty;
   6 use rustc::ty::{DefIdTree, Ty};
   7 use rustc_errors::Applicability;
   8 use rustc_hir as hir;
   9 use rustc_hir::def::{DefKind, Res};
  10 use rustc_hir::intravisit::{walk_item, walk_path, walk_ty, NestedVisitorMap, Visitor};
  11 use rustc_hir::*;
  12 use rustc_session::declare_tool_lint;
  13 use rustc_span::symbol::kw;
  14
  15 use crate::utils::{differing_macro_contexts, span_lint_and_sugg};
  16
  17 declare_clippy_lint! {
  18     /// **What it does:** Checks for unnecessary repetition of structure name when a
  19     /// replacement with `Self` is applicable.
  20     ///
  21     /// **Why is this bad?** Unnecessary repetition. Mixed use of `Self` and struct
  22     /// name
  23     /// feels inconsistent.
  24     ///
  25     /// **Known problems:**
  26     /// - False positive when using associated types (#2843)
  27     /// - False positives in some situations when using generics (#3410)
  28     ///
  29     /// **Example:**
  30     /// ```rust
  31     /// struct Foo {}
  32     /// impl Foo {
  33     ///     fn new() -> Foo {
  34     ///         Foo {}
  35     ///     }
  36     /// }
  37     /// ```
  38     /// could be
  39     /// ```rust
  40     /// struct Foo {}
  41     /// impl Foo {
  42     ///     fn new() -> Self {
  43     ///         Self {}
  44     ///     }
  45     /// }
  46     /// ```
  47     pub USE_SELF,
  48     nursery,
  49     "Unnecessary structure name repetition whereas `Self` is applicable"
  50 }
  51
  52 declare_lint_pass!(UseSelf => [USE_SELF]);
  53
  54 const SEGMENTS_MSG: &str = "segments should be composed of at least 1 element";
  55
  56 fn span_use_self_lint(cx: &LateContext<'_, '_>, path: &Path<'_>, last_segment: Option<&PathSegment<'_>>) {
  57     let last_segment = last_segment.unwrap_or_else(|| path.segments.last().expect(SEGMENTS_MSG));
  58
  59     // Path segments only include actual path, no methods or fields.
  60     let last_path_span = last_segment.ident.span;
  61
  62     if differing_macro_contexts(path.span, last_path_span) {
  63         return;
  64     }
  65
  66     // Only take path up to the end of last_path_span.
  67     let span = path.span.with_hi(last_path_span.hi());
  68
  69     span_lint_and_sugg(
  70         cx,
  71         USE_SELF,
  72         span,
  73         "unnecessary structure name repetition",
  74         "use the applicable keyword",
  75         "Self".to_owned(),
  76         Applicability::MachineApplicable,
  77     );
  78 }
  79
  80 struct TraitImplTyVisitor<'a, 'tcx> {
  81     item_type: Ty<'tcx>,
  82     cx: &'a LateContext<'a, 'tcx>,
  83     trait_type_walker: ty::walk::TypeWalker<'tcx>,
  84     impl_type_walker: ty::walk::TypeWalker<'tcx>,
  85 }
  86
  87 impl<'a, 'tcx> Visitor<'tcx> for TraitImplTyVisitor<'a, 'tcx> {
  88     type Map = Map<'tcx>;
  89
  90     fn visit_ty(&mut self, t: &'tcx hir::Ty<'_>) {
  91         let trait_ty = self.trait_type_walker.next();
  92         let impl_ty = self.impl_type_walker.next();
  93
  94         if_chain! {
  95             if let TyKind::Path(QPath::Resolved(_, path)) = &t.kind;
  96
  97             // The implementation and trait types don't match which means that
  98             // the concrete type was specified by the implementation
  99             if impl_ty != trait_ty;
 100             if let Some(impl_ty) = impl_ty;
 101             if self.item_type == impl_ty;
 102             then {
 103                 match path.res {
 104                     def::Res::SelfTy(..) => {},
 105                     _ => span_use_self_lint(self.cx, path, None)
 106                 }
 107             }
 108         }
 109
 110         walk_ty(self, t)
 111     }
 112
 113     fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
 114         NestedVisitorMap::None
 115     }
 116 }
 117
 118 fn check_trait_method_impl_decl<'a, 'tcx>(
 119     cx: &'a LateContext<'a, 'tcx>,
 120     item_type: Ty<'tcx>,
 121     impl_item: &ImplItem<'_>,
 122     impl_decl: &'tcx FnDecl<'_>,
 123     impl_trait_ref: &ty::TraitRef<'_>,
 124 ) {
 125     let trait_method = cx
 126         .tcx
 127         .associated_items(impl_trait_ref.def_id)
 128         .find(|assoc_item| {
 129             assoc_item.kind == ty::AssocKind::Method
 130                 && cx
 131                     .tcx
 132                     .hygienic_eq(impl_item.ident, assoc_item.ident, impl_trait_ref.def_id)
 133         })
 134         .expect("impl method matches a trait method");
 135
 136     let trait_method_sig = cx.tcx.fn_sig(trait_method.def_id);
 137     let trait_method_sig = cx.tcx.erase_late_bound_regions(&trait_method_sig);
 138
 139     let impl_method_def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
 140     let impl_method_sig = cx.tcx.fn_sig(impl_method_def_id);
 141     let impl_method_sig = cx.tcx.erase_late_bound_regions(&impl_method_sig);
 142
 143     let output_ty = if let FunctionRetTy::Return(ty) = &impl_decl.output {
 144         Some(&**ty)
 145     } else {
 146         None
 147     };
 148
 149     // `impl_decl_ty` (of type `hir::Ty`) represents the type declared in the signature.
 150     // `impl_ty` (of type `ty:TyS`) is the concrete type that the compiler has determined for
 151     // that declaration. We use `impl_decl_ty` to see if the type was declared as `Self`
 152     // and use `impl_ty` to check its concrete type.
 153     for (impl_decl_ty, (impl_ty, trait_ty)) in impl_decl.inputs.iter().chain(output_ty).zip(
 154         impl_method_sig
 155             .inputs_and_output
 156             .iter()
 157             .zip(trait_method_sig.inputs_and_output),
 158     ) {
 159         let mut visitor = TraitImplTyVisitor {
 160             cx,
 161             item_type,
 162             trait_type_walker: trait_ty.walk(),
 163             impl_type_walker: impl_ty.walk(),
 164         };
 165
 166         visitor.visit_ty(&impl_decl_ty);
 167     }
 168 }
 169
 170 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UseSelf {
 171     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item<'_>) {
 172         if in_external_macro(cx.sess(), item.span) {
 173             return;
 174         }
 175         if_chain! {
 176             if let ItemKind::Impl(.., ref item_type, refs) = item.kind;
 177             if let TyKind::Path(QPath::Resolved(_, ref item_path)) = item_type.kind;
 178             then {
 179                 let parameters = &item_path.segments.last().expect(SEGMENTS_MSG).args;
 180                 let should_check = if let Some(ref params) = *parameters {
 181                     !params.parenthesized && !params.args.iter().any(|arg| match arg {
 182                         GenericArg::Lifetime(_) => true,
 183                         _ => false,
 184                     })
 185                 } else {
 186                     true
 187                 };
 188
 189                 if should_check {
 190                     let visitor = &mut UseSelfVisitor {
 191                         item_path,
 192                         cx,
 193                     };
 194                     let impl_def_id = cx.tcx.hir().local_def_id(item.hir_id);
 195                     let impl_trait_ref = cx.tcx.impl_trait_ref(impl_def_id);
 196
 197                     if let Some(impl_trait_ref) = impl_trait_ref {
 198                         for impl_item_ref in refs {
 199                             let impl_item = cx.tcx.hir().impl_item(impl_item_ref.id);
 200                             if let ImplItemKind::Method(FnSig{ decl: impl_decl, .. }, impl_body_id)
 201                                     = &impl_item.kind {
 202                                 let item_type = cx.tcx.type_of(impl_def_id);
 203                                 check_trait_method_impl_decl(cx, item_type, impl_item, impl_decl, &impl_trait_ref);
 204
 205                                 let body = cx.tcx.hir().body(*impl_body_id);
 206                                 visitor.visit_body(body);
 207                             } else {
 208                                 visitor.visit_impl_item(impl_item);
 209                             }
 210                         }
 211                     } else {
 212                         for impl_item_ref in refs {
 213                             let impl_item = cx.tcx.hir().impl_item(impl_item_ref.id);
 214                             visitor.visit_impl_item(impl_item);
 215                         }
 216                     }
 217                 }
 218             }
 219         }
 220     }
 221 }
 222
 223 struct UseSelfVisitor<'a, 'tcx> {
 224     item_path: &'a Path<'a>,
 225     cx: &'a LateContext<'a, 'tcx>,
 226 }
 227
 228 impl<'a, 'tcx> Visitor<'tcx> for UseSelfVisitor<'a, 'tcx> {
 229     type Map = Map<'tcx>;
 230
 231     fn visit_path(&mut self, path: &'tcx Path<'_>, _id: HirId) {
 232         if !path.segments.iter().any(|p| p.ident.span.is_dummy()) {
 233             if path.segments.len() >= 2 {
 234                 let last_but_one = &path.segments[path.segments.len() - 2];
 235                 if last_but_one.ident.name != kw::SelfUpper {
 236                     let enum_def_id = match path.res {
 237                         Res::Def(DefKind::Variant, variant_def_id) => self.cx.tcx.parent(variant_def_id),
 238                         Res::Def(DefKind::Ctor(def::CtorOf::Variant, _), ctor_def_id) => {
 239                             let variant_def_id = self.cx.tcx.parent(ctor_def_id);
 240                             variant_def_id.and_then(|def_id| self.cx.tcx.parent(def_id))
 241                         },
 242                         _ => None,
 243                     };
 244
 245                     if self.item_path.res.opt_def_id() == enum_def_id {
 246                         span_use_self_lint(self.cx, path, Some(last_but_one));
 247                     }
 248                 }
 249             }
 250
 251             if path.segments.last().expect(SEGMENTS_MSG).ident.name != kw::SelfUpper {
 252                 if self.item_path.res == path.res {
 253                     span_use_self_lint(self.cx, path, None);
 254                 } else if let Res::Def(DefKind::Ctor(def::CtorOf::Struct, _), ctor_def_id) = path.res {
 255                     if self.item_path.res.opt_def_id() == self.cx.tcx.parent(ctor_def_id) {
 256                         span_use_self_lint(self.cx, path, None);
 257                     }
 258                 }
 259             }
 260         }
 261
 262         walk_path(self, path);
 263     }
 264
 265     fn visit_item(&mut self, item: &'tcx Item<'_>) {
 266         match item.kind {
 267             ItemKind::Use(..)
 268             | ItemKind::Static(..)
 269             | ItemKind::Enum(..)
 270             | ItemKind::Struct(..)
 271             | ItemKind::Union(..)
 272             | ItemKind::Impl(..)
 273             | ItemKind::Fn(..) => {
 274                 // Don't check statements that shadow `Self` or where `Self` can't be used
 275             },
 276             _ => walk_item(self, item),
 277         }
 278     }
 279
 280     fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
 281         NestedVisitorMap::All(&self.cx.tcx.hir())
 282     }
 283 }