clippy_lints/src/use_self.rs

   1 use if_chain::if_chain;
   2 use rustc::hir;
   3 use rustc::hir::def::{CtorKind, 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) {
  55     // Path segments only include actual path, no methods or fields.
  56     let last_path_span = path.segments.last().expect(SEGMENTS_MSG).ident.span;
  57     // Only take path up to the end of last_path_span.
  58     let span = path.span.with_hi(last_path_span.hi());
  59
  60     span_lint_and_sugg(
  61         cx,
  62         USE_SELF,
  63         span,
  64         "unnecessary structure name repetition",
  65         "use the applicable keyword",
  66         "Self".to_owned(),
  67         Applicability::MachineApplicable,
  68     );
  69 }
  70
  71 struct TraitImplTyVisitor<'a, 'tcx> {
  72     item_type: Ty<'tcx>,
  73     cx: &'a LateContext<'a, 'tcx>,
  74     trait_type_walker: ty::walk::TypeWalker<'tcx>,
  75     impl_type_walker: ty::walk::TypeWalker<'tcx>,
  76 }
  77
  78 impl<'a, 'tcx> Visitor<'tcx> for TraitImplTyVisitor<'a, 'tcx> {
  79     fn visit_ty(&mut self, t: &'tcx hir::Ty) {
  80         let trait_ty = self.trait_type_walker.next();
  81         let impl_ty = self.impl_type_walker.next();
  82
  83         if let TyKind::Path(QPath::Resolved(_, path)) = &t.node {
  84             // The implementation and trait types don't match which means that
  85             // the concrete type was specified by the implementation
  86             if impl_ty != trait_ty {
  87                 if let Some(impl_ty) = impl_ty {
  88                     if self.item_type == impl_ty {
  89                         let is_self_ty = if let def::Res::SelfTy(..) = path.res {
  90                             true
  91                         } else {
  92                             false
  93                         };
  94
  95                         if !is_self_ty {
  96                             span_use_self_lint(self.cx, path);
  97                         }
  98                     }
  99                 }
 100             }
 101         }
 102
 103         walk_ty(self, t)
 104     }
 105
 106     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 107         NestedVisitorMap::None
 108     }
 109 }
 110
 111 fn check_trait_method_impl_decl<'a, 'tcx>(
 112     cx: &'a LateContext<'a, 'tcx>,
 113     item_type: Ty<'tcx>,
 114     impl_item: &ImplItem,
 115     impl_decl: &'tcx FnDecl,
 116     impl_trait_ref: &ty::TraitRef<'_>,
 117 ) {
 118     let trait_method = cx
 119         .tcx
 120         .associated_items(impl_trait_ref.def_id)
 121         .find(|assoc_item| {
 122             assoc_item.kind == ty::AssocKind::Method
 123                 && cx
 124                     .tcx
 125                     .hygienic_eq(impl_item.ident, assoc_item.ident, impl_trait_ref.def_id)
 126         })
 127         .expect("impl method matches a trait method");
 128
 129     let trait_method_sig = cx.tcx.fn_sig(trait_method.def_id);
 130     let trait_method_sig = cx.tcx.erase_late_bound_regions(&trait_method_sig);
 131
 132     let impl_method_def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
 133     let impl_method_sig = cx.tcx.fn_sig(impl_method_def_id);
 134     let impl_method_sig = cx.tcx.erase_late_bound_regions(&impl_method_sig);
 135
 136     let output_ty = if let FunctionRetTy::Return(ty) = &impl_decl.output {
 137         Some(&**ty)
 138     } else {
 139         None
 140     };
 141
 142     // `impl_decl_ty` (of type `hir::Ty`) represents the type declared in the signature.
 143     // `impl_ty` (of type `ty:TyS`) is the concrete type that the compiler has determined for
 144     // that declaration. We use `impl_decl_ty` to see if the type was declared as `Self`
 145     // and use `impl_ty` to check its concrete type.
 146     for (impl_decl_ty, (impl_ty, trait_ty)) in impl_decl.inputs.iter().chain(output_ty).zip(
 147         impl_method_sig
 148             .inputs_and_output
 149             .iter()
 150             .zip(trait_method_sig.inputs_and_output),
 151     ) {
 152         let mut visitor = TraitImplTyVisitor {
 153             cx,
 154             item_type,
 155             trait_type_walker: trait_ty.walk(),
 156             impl_type_walker: impl_ty.walk(),
 157         };
 158
 159         visitor.visit_ty(&impl_decl_ty);
 160     }
 161 }
 162
 163 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UseSelf {
 164     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
 165         if in_external_macro(cx.sess(), item.span) {
 166             return;
 167         }
 168         if_chain! {
 169             if let ItemKind::Impl(.., ref item_type, ref refs) = item.node;
 170             if let TyKind::Path(QPath::Resolved(_, ref item_path)) = item_type.node;
 171             then {
 172                 let parameters = &item_path.segments.last().expect(SEGMENTS_MSG).args;
 173                 let should_check = if let Some(ref params) = *parameters {
 174                     !params.parenthesized && !params.args.iter().any(|arg| match arg {
 175                         GenericArg::Lifetime(_) => true,
 176                         _ => false,
 177                     })
 178                 } else {
 179                     true
 180                 };
 181
 182                 if should_check {
 183                     let visitor = &mut UseSelfVisitor {
 184                         item_path,
 185                         cx,
 186                     };
 187                     let impl_def_id = cx.tcx.hir().local_def_id(item.hir_id);
 188                     let impl_trait_ref = cx.tcx.impl_trait_ref(impl_def_id);
 189
 190                     if let Some(impl_trait_ref) = impl_trait_ref {
 191                         for impl_item_ref in refs {
 192                             let impl_item = cx.tcx.hir().impl_item(impl_item_ref.id);
 193                             if let ImplItemKind::Method(MethodSig{ decl: impl_decl, .. }, impl_body_id)
 194                                     = &impl_item.node {
 195                                 let item_type = cx.tcx.type_of(impl_def_id);
 196                                 check_trait_method_impl_decl(cx, item_type, impl_item, impl_decl, &impl_trait_ref);
 197
 198                                 let body = cx.tcx.hir().body(*impl_body_id);
 199                                 visitor.visit_body(body);
 200                             } else {
 201                                 visitor.visit_impl_item(impl_item);
 202                             }
 203                         }
 204                     } else {
 205                         for impl_item_ref in refs {
 206                             let impl_item = cx.tcx.hir().impl_item(impl_item_ref.id);
 207                             visitor.visit_impl_item(impl_item);
 208                         }
 209                     }
 210                 }
 211             }
 212         }
 213     }
 214 }
 215
 216 struct UseSelfVisitor<'a, 'tcx> {
 217     item_path: &'a Path,
 218     cx: &'a LateContext<'a, 'tcx>,
 219 }
 220
 221 impl<'a, 'tcx> Visitor<'tcx> for UseSelfVisitor<'a, 'tcx> {
 222     fn visit_path(&mut self, path: &'tcx Path, _id: HirId) {
 223         if path.segments.last().expect(SEGMENTS_MSG).ident.name != kw::SelfUpper {
 224             if self.item_path.res == path.res {
 225                 span_use_self_lint(self.cx, path);
 226             } else if let Res::Def(DefKind::Ctor(def::CtorOf::Struct, CtorKind::Fn), ctor_did) = path.res {
 227                 if self.item_path.res.opt_def_id() == self.cx.tcx.parent(ctor_did) {
 228                     span_use_self_lint(self.cx, path);
 229                 }
 230             }
 231         }
 232         walk_path(self, path);
 233     }
 234
 235     fn visit_item(&mut self, item: &'tcx Item) {
 236         match item.node {
 237             ItemKind::Use(..)
 238             | ItemKind::Static(..)
 239             | ItemKind::Enum(..)
 240             | ItemKind::Struct(..)
 241             | ItemKind::Union(..)
 242             | ItemKind::Impl(..)
 243             | ItemKind::Fn(..) => {
 244                 // Don't check statements that shadow `Self` or where `Self` can't be used
 245             },
 246             _ => walk_item(self, item),
 247         }
 248     }
 249
 250     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 251         NestedVisitorMap::All(&self.cx.tcx.hir())
 252     }
 253 }