clippy_lints/src/use_self.rs

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