clippy_lints/src/use_self.rs

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