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