clippy_lints/src/use_self.rs

   1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution.
   3 //
   4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   7 // option. This file may not be copied, modified, or distributed
   8 // except according to those terms.
   9
  10 use crate::utils::{in_macro, span_lint_and_sugg};
  11 use if_chain::if_chain;
  12 use rustc::hir::intravisit::{walk_path, walk_ty, NestedVisitorMap, Visitor};
  13 use rustc::hir::*;
  14 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
  15 use rustc::ty;
  16 use rustc::{declare_tool_lint, lint_array};
  17 use rustc_errors::Applicability;
  18 use syntax::ast::NodeId;
  19 use syntax_pos::symbol::keywords::SelfUpper;
  20
  21 /// **What it does:** Checks for unnecessary repetition of structure name when a
  22 /// replacement with `Self` is applicable.
  23 ///
  24 /// **Why is this bad?** Unnecessary repetition. Mixed use of `Self` and struct
  25 /// name
  26 /// feels inconsistent.
  27 ///
  28 /// **Known problems:** None.
  29 ///
  30 /// **Example:**
  31 /// ```rust
  32 /// struct Foo {}
  33 /// impl Foo {
  34 ///     fn new() -> Foo {
  35 ///         Foo {}
  36 ///     }
  37 /// }
  38 /// ```
  39 /// could be
  40 /// ```rust
  41 /// struct Foo {}
  42 /// impl Foo {
  43 ///     fn new() -> Self {
  44 ///         Self {}
  45 ///     }
  46 /// }
  47 /// ```
  48 declare_clippy_lint! {
  49     pub USE_SELF,
  50     pedantic,
  51     "Unnecessary structure name repetition whereas `Self` is applicable"
  52 }
  53
  54 #[derive(Copy, Clone, Default)]
  55 pub struct UseSelf;
  56
  57 impl LintPass for UseSelf {
  58     fn get_lints(&self) -> LintArray {
  59         lint_array!(USE_SELF)
  60     }
  61 }
  62
  63 const SEGMENTS_MSG: &str = "segments should be composed of at least 1 element";
  64
  65 fn span_use_self_lint(cx: &LateContext<'_, '_>, path: &Path) {
  66     span_lint_and_sugg(
  67         cx,
  68         USE_SELF,
  69         path.span,
  70         "unnecessary structure name repetition",
  71         "use the applicable keyword",
  72         "Self".to_owned(),
  73         Applicability::MachineApplicable,
  74     );
  75 }
  76
  77 struct TraitImplTyVisitor<'a, 'tcx: 'a> {
  78     item_type: ty::Ty<'tcx>,
  79     cx: &'a LateContext<'a, 'tcx>,
  80     trait_type_walker: ty::walk::TypeWalker<'tcx>,
  81     impl_type_walker: ty::walk::TypeWalker<'tcx>,
  82 }
  83
  84 impl<'a, 'tcx> Visitor<'tcx> for TraitImplTyVisitor<'a, 'tcx> {
  85     fn visit_ty(&mut self, t: &'tcx Ty) {
  86         let trait_ty = self.trait_type_walker.next();
  87         let impl_ty = self.impl_type_walker.next();
  88
  89         if let TyKind::Path(QPath::Resolved(_, path)) = &t.node {
  90             // The implementation and trait types don't match which means that
  91             // the concrete type was specified by the implementation
  92             if impl_ty != trait_ty {
  93                 if let Some(impl_ty) = impl_ty {
  94                     if self.item_type == impl_ty {
  95                         let is_self_ty = if let def::Def::SelfTy(..) = path.def {
  96                             true
  97                         } else {
  98                             false
  99                         };
 100
 101                         if !is_self_ty {
 102                             span_use_self_lint(self.cx, path);
 103                         }
 104                     }
 105                 }
 106             }
 107         }
 108
 109         walk_ty(self, t)
 110     }
 111
 112     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 113         NestedVisitorMap::None
 114     }
 115 }
 116
 117 fn check_trait_method_impl_decl<'a, 'tcx: 'a>(
 118     cx: &'a LateContext<'a, 'tcx>,
 119     item_type: ty::Ty<'tcx>,
 120     impl_item: &ImplItem,
 121     impl_decl: &'tcx FnDecl,
 122     impl_trait_ref: &ty::TraitRef<'_>,
 123 ) {
 124     let trait_method = cx
 125         .tcx
 126         .associated_items(impl_trait_ref.def_id)
 127         .find(|assoc_item| {
 128             assoc_item.kind == ty::AssociatedKind::Method
 129                 && cx
 130                     .tcx
 131                     .hygienic_eq(impl_item.ident, assoc_item.ident, impl_trait_ref.def_id)
 132         })
 133         .expect("impl method matches a trait method");
 134
 135     let trait_method_sig = cx.tcx.fn_sig(trait_method.def_id);
 136     let trait_method_sig = cx.tcx.erase_late_bound_regions(&trait_method_sig);
 137
 138     let impl_method_def_id = cx.tcx.hir().local_def_id(impl_item.id);
 139     let impl_method_sig = cx.tcx.fn_sig(impl_method_def_id);
 140     let impl_method_sig = cx.tcx.erase_late_bound_regions(&impl_method_sig);
 141
 142     let output_ty = if let FunctionRetTy::Return(ty) = &impl_decl.output {
 143         Some(&**ty)
 144     } else {
 145         None
 146     };
 147
 148     // `impl_decl_ty` (of type `hir::Ty`) represents the type declared in the signature.
 149     // `impl_ty` (of type `ty:TyS`) is the concrete type that the compiler has determined for
 150     // that declaration.  We use `impl_decl_ty` to see if the type was declared as `Self`
 151     // and use `impl_ty` to check its concrete type.
 152     for (impl_decl_ty, (impl_ty, trait_ty)) in impl_decl.inputs.iter().chain(output_ty).zip(
 153         impl_method_sig
 154             .inputs_and_output
 155             .iter()
 156             .zip(trait_method_sig.inputs_and_output),
 157     ) {
 158         let mut visitor = TraitImplTyVisitor {
 159             cx,
 160             item_type,
 161             trait_type_walker: trait_ty.walk(),
 162             impl_type_walker: impl_ty.walk(),
 163         };
 164
 165         visitor.visit_ty(&impl_decl_ty);
 166     }
 167 }
 168
 169 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UseSelf {
 170     fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
 171         if in_macro(item.span) {
 172             return;
 173         }
 174         if_chain! {
 175             if let ItemKind::Impl(.., ref item_type, ref refs) = item.node;
 176             if let TyKind::Path(QPath::Resolved(_, ref item_path)) = item_type.node;
 177             then {
 178                 let parameters = &item_path.segments.last().expect(SEGMENTS_MSG).args;
 179                 let should_check = if let Some(ref params) = *parameters {
 180                     !params.parenthesized && !params.args.iter().any(|arg| match arg {
 181                         GenericArg::Lifetime(_) => true,
 182                         GenericArg::Type(_) => false,
 183                     })
 184                 } else {
 185                     true
 186                 };
 187
 188                 if should_check {
 189                     let visitor = &mut UseSelfVisitor {
 190                         item_path,
 191                         cx,
 192                     };
 193                     let impl_def_id = cx.tcx.hir().local_def_id(item.id);
 194                     let impl_trait_ref = cx.tcx.impl_trait_ref(impl_def_id);
 195
 196                     if let Some(impl_trait_ref) = impl_trait_ref {
 197                         for impl_item_ref in refs {
 198                             let impl_item = cx.tcx.hir().impl_item(impl_item_ref.id);
 199                             if let ImplItemKind::Method(MethodSig{ decl: impl_decl, .. }, impl_body_id)
 200                                     = &impl_item.node {
 201                                 let item_type = cx.tcx.type_of(impl_def_id);
 202                                 check_trait_method_impl_decl(cx, item_type, impl_item, impl_decl, &impl_trait_ref);
 203
 204                                 let body = cx.tcx.hir().body(*impl_body_id);
 205                                 visitor.visit_body(body);
 206                             } else {
 207                                 visitor.visit_impl_item(impl_item);
 208                             }
 209                         }
 210                     } else {
 211                         for impl_item_ref in refs {
 212                             let impl_item = cx.tcx.hir().impl_item(impl_item_ref.id);
 213                             visitor.visit_impl_item(impl_item);
 214                         }
 215                     }
 216                 }
 217             }
 218         }
 219     }
 220 }
 221
 222 struct UseSelfVisitor<'a, 'tcx: 'a> {
 223     item_path: &'a Path,
 224     cx: &'a LateContext<'a, 'tcx>,
 225 }
 226
 227 impl<'a, 'tcx> Visitor<'tcx> for UseSelfVisitor<'a, 'tcx> {
 228     fn visit_path(&mut self, path: &'tcx Path, _id: HirId) {
 229         if self.item_path.def == path.def && path.segments.last().expect(SEGMENTS_MSG).ident.name != SelfUpper.name() {
 230             span_use_self_lint(self.cx, path);
 231         }
 232
 233         walk_path(self, path);
 234     }
 235
 236     fn visit_use(&mut self, _path: &'tcx Path, _id: NodeId, _hir_id: HirId) {
 237         // Don't check use statements
 238     }
 239
 240     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 241         NestedVisitorMap::All(&self.cx.tcx.hir())
 242     }
 243 }