clippy_lints/src/use_self.rs

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