clippy_lints/src/use_self.rs

   1 use crate::utils::span_lint_and_sugg;
   2 use if_chain::if_chain;
   3 use rustc::hir::def::{CtorKind, Def};
   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::{declare_tool_lint, lint_array};
   9 use rustc_errors::Applicability;
  10 use syntax_pos::{symbol::keywords::SelfUpper, Span};
  11
  12 /// **What it does:** Checks for unnecessary repetition of structure name when a
  13 /// replacement with `Self` is applicable.
  14 ///
  15 /// **Why is this bad?** Unnecessary repetition. Mixed use of `Self` and struct
  16 /// name
  17 /// feels inconsistent.
  18 ///
  19 /// **Known problems:**
  20 /// - False positive when using associated types (#2843)
  21 /// - False positives in some situations when using generics (#3410)
  22 ///
  23 /// **Example:**
  24 /// ```rust
  25 /// struct Foo {}
  26 /// impl Foo {
  27 ///     fn new() -> Foo {
  28 ///         Foo {}
  29 ///     }
  30 /// }
  31 /// ```
  32 /// could be
  33 /// ```rust
  34 /// struct Foo {}
  35 /// impl Foo {
  36 ///     fn new() -> Self {
  37 ///         Self {}
  38 ///     }
  39 /// }
  40 /// ```
  41 declare_clippy_lint! {
  42     pub USE_SELF,
  43     pedantic,
  44     "Unnecessary structure name repetition whereas `Self` is applicable"
  45 }
  46
  47 #[derive(Copy, Clone, Default)]
  48 pub struct UseSelf;
  49
  50 impl LintPass for UseSelf {
  51     fn get_lints(&self) -> LintArray {
  52         lint_array!(USE_SELF)
  53     }
  54 }
  55
  56 const SEGMENTS_MSG: &str = "segments should be composed of at least 1 element";
  57
  58 fn span_use_self_lint(cx: &LateContext<'_, '_>, span: Span) {
  59     span_lint_and_sugg(
  60         cx,
  61         USE_SELF,
  62         span,
  63         "unnecessary structure name repetition",
  64         "use the applicable keyword",
  65         "Self".to_owned(),
  66         Applicability::MachineApplicable,
  67     );
  68 }
  69
  70 struct TraitImplTyVisitor<'a, 'tcx: 'a> {
  71     item_type: ty::Ty<'tcx>,
  72     cx: &'a LateContext<'a, 'tcx>,
  73     trait_type_walker: ty::walk::TypeWalker<'tcx>,
  74     impl_type_walker: ty::walk::TypeWalker<'tcx>,
  75 }
  76
  77 impl<'a, 'tcx> Visitor<'tcx> for TraitImplTyVisitor<'a, 'tcx> {
  78     fn visit_ty(&mut self, t: &'tcx Ty) {
  79         let trait_ty = self.trait_type_walker.next();
  80         let impl_ty = self.impl_type_walker.next();
  81
  82         if let TyKind::Path(QPath::Resolved(_, path)) = &t.node {
  83             // The implementation and trait types don't match which means that
  84             // the concrete type was specified by the implementation
  85             if impl_ty != trait_ty {
  86                 if let Some(impl_ty) = impl_ty {
  87                     if self.item_type == impl_ty {
  88                         let is_self_ty = if let def::Def::SelfTy(..) = path.def {
  89                             true
  90                         } else {
  91                             false
  92                         };
  93
  94                         if !is_self_ty {
  95                             span_use_self_lint(self.cx, path.span);
  96                         }
  97                     }
  98                 }
  99             }
 100         }
 101
 102         walk_ty(self, t)
 103     }
 104
 105     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 106         NestedVisitorMap::None
 107     }
 108 }
 109
 110 fn check_trait_method_impl_decl<'a, 'tcx: 'a>(
 111     cx: &'a LateContext<'a, 'tcx>,
 112     item_type: ty::Ty<'tcx>,
 113     impl_item: &ImplItem,
 114     impl_decl: &'tcx FnDecl,
 115     impl_trait_ref: &ty::TraitRef<'_>,
 116 ) {
 117     let trait_method = cx
 118         .tcx
 119         .associated_items(impl_trait_ref.def_id)
 120         .find(|assoc_item| {
 121             assoc_item.kind == ty::AssociatedKind::Method
 122                 && cx
 123                     .tcx
 124                     .hygienic_eq(impl_item.ident, assoc_item.ident, impl_trait_ref.def_id)
 125         })
 126         .expect("impl method matches a trait method");
 127
 128     let trait_method_sig = cx.tcx.fn_sig(trait_method.def_id);
 129     let trait_method_sig = cx.tcx.erase_late_bound_regions(&trait_method_sig);
 130
 131     let impl_method_def_id = cx.tcx.hir().local_def_id(impl_item.id);
 132     let impl_method_sig = cx.tcx.fn_sig(impl_method_def_id);
 133     let impl_method_sig = cx.tcx.erase_late_bound_regions(&impl_method_sig);
 134
 135     let output_ty = if let FunctionRetTy::Return(ty) = &impl_decl.output {
 136         Some(&**ty)
 137     } else {
 138         None
 139     };
 140
 141     // `impl_decl_ty` (of type `hir::Ty`) represents the type declared in the signature.
 142     // `impl_ty` (of type `ty:TyS`) is the concrete type that the compiler has determined for
 143     // that declaration.  We use `impl_decl_ty` to see if the type was declared as `Self`
 144     // and use `impl_ty` to check its concrete type.
 145     for (impl_decl_ty, (impl_ty, trait_ty)) in impl_decl.inputs.iter().chain(output_ty).zip(
 146         impl_method_sig
 147             .inputs_and_output
 148             .iter()
 149             .zip(trait_method_sig.inputs_and_output),
 150     ) {
 151         let mut visitor = TraitImplTyVisitor {
 152             cx,
 153             item_type,
 154             trait_type_walker: trait_ty.walk(),
 155             impl_type_walker: impl_ty.walk(),
 156         };
 157
 158         visitor.visit_ty(&impl_decl_ty);
 159     }
 160 }
 161
 162 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UseSelf {
 163     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
 164         if in_external_macro(cx.sess(), item.span) {
 165             return;
 166         }
 167         if_chain! {
 168             if let ItemKind::Impl(.., ref item_type, ref refs) = item.node;
 169             if let TyKind::Path(QPath::Resolved(_, ref item_path)) = item_type.node;
 170             then {
 171                 let parameters = &item_path.segments.last().expect(SEGMENTS_MSG).args;
 172                 let should_check = if let Some(ref params) = *parameters {
 173                     !params.parenthesized && !params.args.iter().any(|arg| match arg {
 174                         GenericArg::Lifetime(_) => true,
 175                         GenericArg::Type(_) => false,
 176                     })
 177                 } else {
 178                     true
 179                 };
 180
 181                 if should_check {
 182                     let visitor = &mut UseSelfVisitor {
 183                         item_path,
 184                         cx,
 185                     };
 186                     let impl_def_id = cx.tcx.hir().local_def_id(item.id);
 187                     let impl_trait_ref = cx.tcx.impl_trait_ref(impl_def_id);
 188
 189                     if let Some(impl_trait_ref) = impl_trait_ref {
 190                         for impl_item_ref in refs {
 191                             let impl_item = cx.tcx.hir().impl_item(impl_item_ref.id);
 192                             if let ImplItemKind::Method(MethodSig{ decl: impl_decl, .. }, impl_body_id)
 193                                     = &impl_item.node {
 194                                 let item_type = cx.tcx.type_of(impl_def_id);
 195                                 check_trait_method_impl_decl(cx, item_type, impl_item, impl_decl, &impl_trait_ref);
 196
 197                                 let body = cx.tcx.hir().body(*impl_body_id);
 198                                 visitor.visit_body(body);
 199                             } else {
 200                                 visitor.visit_impl_item(impl_item);
 201                             }
 202                         }
 203                     } else {
 204                         for impl_item_ref in refs {
 205                             let impl_item = cx.tcx.hir().impl_item(impl_item_ref.id);
 206                             visitor.visit_impl_item(impl_item);
 207                         }
 208                     }
 209                 }
 210             }
 211         }
 212     }
 213 }
 214
 215 struct UseSelfVisitor<'a, 'tcx: 'a> {
 216     item_path: &'a Path,
 217     cx: &'a LateContext<'a, 'tcx>,
 218 }
 219
 220 impl<'a, 'tcx> Visitor<'tcx> for UseSelfVisitor<'a, 'tcx> {
 221     fn visit_path(&mut self, path: &'tcx Path, _id: HirId) {
 222         if path.segments.last().expect(SEGMENTS_MSG).ident.name != SelfUpper.name() {
 223             if self.item_path.def == path.def {
 224                 span_use_self_lint(self.cx, path.segments.first().expect(SEGMENTS_MSG).ident.span);
 225             } else if let Def::StructCtor(ctor_did, CtorKind::Fn) = path.def {
 226                 if self.item_path.def.opt_def_id() == self.cx.tcx.parent_def_id(ctor_did) {
 227                     span_use_self_lint(self.cx, path.span);
 228                 }
 229             }
 230         }
 231         walk_path(self, path);
 232     }
 233
 234     fn visit_item(&mut self, item: &'tcx Item) {
 235         match item.node {
 236             ItemKind::Use(..)
 237             | ItemKind::Static(..)
 238             | ItemKind::Enum(..)
 239             | ItemKind::Struct(..)
 240             | ItemKind::Union(..)
 241             | ItemKind::Impl(..) => {
 242                 // Don't check statements that shadow `Self` or where `Self` can't be used
 243             },
 244             _ => walk_item(self, item),
 245         }
 246     }
 247
 248     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 249         NestedVisitorMap::All(&self.cx.tcx.hir())
 250     }
 251 }