clippy_lints/src/use_self.rs

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