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