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;
  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<'_, '_>, path: &Path) {
  59     // path segments only include actual path, no methods or fields
  60     let last_path_span = path.segments.last().expect(SEGMENTS_MSG).ident.span;
  61     // `to()` doesn't shorten span, so we shorten it with `until(..)`
  62     // and then include it with `to(..)`
  63     let span = path.span.until(last_path_span).to(last_path_span);
  64
  65     span_lint_and_sugg(
  66         cx,
  67         USE_SELF,
  68         span,
  69         "unnecessary structure name repetition",
  70         "use the applicable keyword",
  71         "Self".to_owned(),
  72         Applicability::MachineApplicable,
  73     );
  74 }
  75
  76 struct TraitImplTyVisitor<'a, 'tcx: 'a> {
  77     item_type: ty::Ty<'tcx>,
  78     cx: &'a LateContext<'a, 'tcx>,
  79     trait_type_walker: ty::walk::TypeWalker<'tcx>,
  80     impl_type_walker: ty::walk::TypeWalker<'tcx>,
  81 }
  82
  83 impl<'a, 'tcx> Visitor<'tcx> for TraitImplTyVisitor<'a, 'tcx> {
  84     fn visit_ty(&mut self, t: &'tcx Ty) {
  85         let trait_ty = self.trait_type_walker.next();
  86         let impl_ty = self.impl_type_walker.next();
  87
  88         if let TyKind::Path(QPath::Resolved(_, path)) = &t.node {
  89             // The implementation and trait types don't match which means that
  90             // the concrete type was specified by the implementation
  91             if impl_ty != trait_ty {
  92                 if let Some(impl_ty) = impl_ty {
  93                     if self.item_type == impl_ty {
  94                         let is_self_ty = if let def::Def::SelfTy(..) = path.def {
  95                             true
  96                         } else {
  97                             false
  98                         };
  99
 100                         if !is_self_ty {
 101                             span_use_self_lint(self.cx, path);
 102                         }
 103                     }
 104                 }
 105             }
 106         }
 107
 108         walk_ty(self, t)
 109     }
 110
 111     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 112         NestedVisitorMap::None
 113     }
 114 }
 115
 116 fn check_trait_method_impl_decl<'a, 'tcx: 'a>(
 117     cx: &'a LateContext<'a, 'tcx>,
 118     item_type: ty::Ty<'tcx>,
 119     impl_item: &ImplItem,
 120     impl_decl: &'tcx FnDecl,
 121     impl_trait_ref: &ty::TraitRef<'_>,
 122 ) {
 123     let trait_method = cx
 124         .tcx
 125         .associated_items(impl_trait_ref.def_id)
 126         .find(|assoc_item| {
 127             assoc_item.kind == ty::AssociatedKind::Method
 128                 && cx
 129                     .tcx
 130                     .hygienic_eq(impl_item.ident, assoc_item.ident, impl_trait_ref.def_id)
 131         })
 132         .expect("impl method matches a trait method");
 133
 134     let trait_method_sig = cx.tcx.fn_sig(trait_method.def_id);
 135     let trait_method_sig = cx.tcx.erase_late_bound_regions(&trait_method_sig);
 136
 137     let impl_method_def_id = cx.tcx.hir().local_def_id(impl_item.id);
 138     let impl_method_sig = cx.tcx.fn_sig(impl_method_def_id);
 139     let impl_method_sig = cx.tcx.erase_late_bound_regions(&impl_method_sig);
 140
 141     let output_ty = if let FunctionRetTy::Return(ty) = &impl_decl.output {
 142         Some(&**ty)
 143     } else {
 144         None
 145     };
 146
 147     // `impl_decl_ty` (of type `hir::Ty`) represents the type declared in the signature.
 148     // `impl_ty` (of type `ty:TyS`) is the concrete type that the compiler has determined for
 149     // that declaration.  We use `impl_decl_ty` to see if the type was declared as `Self`
 150     // and use `impl_ty` to check its concrete type.
 151     for (impl_decl_ty, (impl_ty, trait_ty)) in impl_decl.inputs.iter().chain(output_ty).zip(
 152         impl_method_sig
 153             .inputs_and_output
 154             .iter()
 155             .zip(trait_method_sig.inputs_and_output),
 156     ) {
 157         let mut visitor = TraitImplTyVisitor {
 158             cx,
 159             item_type,
 160             trait_type_walker: trait_ty.walk(),
 161             impl_type_walker: impl_ty.walk(),
 162         };
 163
 164         visitor.visit_ty(&impl_decl_ty);
 165     }
 166 }
 167
 168 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UseSelf {
 169     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
 170         if in_external_macro(cx.sess(), item.span) {
 171             return;
 172         }
 173         if_chain! {
 174             if let ItemKind::Impl(.., ref item_type, ref refs) = item.node;
 175             if let TyKind::Path(QPath::Resolved(_, ref item_path)) = item_type.node;
 176             then {
 177                 let parameters = &item_path.segments.last().expect(SEGMENTS_MSG).args;
 178                 let should_check = if let Some(ref params) = *parameters {
 179                     !params.parenthesized && !params.args.iter().any(|arg| match arg {
 180                         GenericArg::Lifetime(_) => true,
 181                         GenericArg::Type(_) => false,
 182                     })
 183                 } else {
 184                     true
 185                 };
 186
 187                 if should_check {
 188                     let visitor = &mut UseSelfVisitor {
 189                         item_path,
 190                         cx,
 191                     };
 192                     let impl_def_id = cx.tcx.hir().local_def_id(item.id);
 193                     let impl_trait_ref = cx.tcx.impl_trait_ref(impl_def_id);
 194
 195                     if let Some(impl_trait_ref) = impl_trait_ref {
 196                         for impl_item_ref in refs {
 197                             let impl_item = cx.tcx.hir().impl_item(impl_item_ref.id);
 198                             if let ImplItemKind::Method(MethodSig{ decl: impl_decl, .. }, impl_body_id)
 199                                     = &impl_item.node {
 200                                 let item_type = cx.tcx.type_of(impl_def_id);
 201                                 check_trait_method_impl_decl(cx, item_type, impl_item, impl_decl, &impl_trait_ref);
 202
 203                                 let body = cx.tcx.hir().body(*impl_body_id);
 204                                 visitor.visit_body(body);
 205                             } else {
 206                                 visitor.visit_impl_item(impl_item);
 207                             }
 208                         }
 209                     } else {
 210                         for impl_item_ref in refs {
 211                             let impl_item = cx.tcx.hir().impl_item(impl_item_ref.id);
 212                             visitor.visit_impl_item(impl_item);
 213                         }
 214                     }
 215                 }
 216             }
 217         }
 218     }
 219 }
 220
 221 struct UseSelfVisitor<'a, 'tcx: 'a> {
 222     item_path: &'a Path,
 223     cx: &'a LateContext<'a, 'tcx>,
 224 }
 225
 226 impl<'a, 'tcx> Visitor<'tcx> for UseSelfVisitor<'a, 'tcx> {
 227     fn visit_path(&mut self, path: &'tcx Path, _id: HirId) {
 228         if path.segments.last().expect(SEGMENTS_MSG).ident.name != SelfUpper.name() {
 229             if self.item_path.def == path.def {
 230                 span_use_self_lint(self.cx, path);
 231             } else if let Def::StructCtor(ctor_did, CtorKind::Fn) = path.def {
 232                 if self.item_path.def.opt_def_id() == self.cx.tcx.parent_def_id(ctor_did) {
 233                     span_use_self_lint(self.cx, path);
 234                 }
 235             }
 236         }
 237         walk_path(self, path);
 238     }
 239
 240     fn visit_item(&mut self, item: &'tcx Item) {
 241         match item.node {
 242             ItemKind::Use(..)
 243             | ItemKind::Static(..)
 244             | ItemKind::Enum(..)
 245             | ItemKind::Struct(..)
 246             | ItemKind::Union(..)
 247             | ItemKind::Impl(..) => {
 248                 // Don't check statements that shadow `Self` or where `Self` can't be used
 249             },
 250             _ => walk_item(self, item),
 251         }
 252     }
 253
 254     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 255         NestedVisitorMap::All(&self.cx.tcx.hir())
 256     }
 257 }