clippy_lints/src/same_name_method.rs

   1 use clippy_utils::diagnostics::span_lint_and_then;
   2 use rustc_data_structures::fx::FxHashMap;
   3 use rustc_hir::def::{DefKind, Res};
   4 use rustc_hir::{Impl, ItemKind, Node, Path, QPath, TraitRef, TyKind};
   5 use rustc_lint::{LateContext, LateLintPass};
   6 use rustc_middle::ty::AssocKind;
   7 use rustc_session::{declare_lint_pass, declare_tool_lint};
   8 use rustc_span::symbol::Symbol;
   9 use rustc_span::Span;
  10 use std::collections::{BTreeMap, BTreeSet};
  11
  12 declare_clippy_lint! {
  13     /// ### What it does
  14     /// It lints if a struct has two methods with the same name:
  15     /// one from a trait, another not from trait.
  16     ///
  17     /// ### Why is this bad?
  18     /// Confusing.
  19     ///
  20     /// ### Example
  21     /// ```rust
  22     /// trait T {
  23     ///     fn foo(&self) {}
  24     /// }
  25     ///
  26     /// struct S;
  27     ///
  28     /// impl T for S {
  29     ///     fn foo(&self) {}
  30     /// }
  31     ///
  32     /// impl S {
  33     ///     fn foo(&self) {}
  34     /// }
  35     /// ```
  36     #[clippy::version = "1.57.0"]
  37     pub SAME_NAME_METHOD,
  38     restriction,
  39     "two method with same name"
  40 }
  41
  42 declare_lint_pass!(SameNameMethod => [SAME_NAME_METHOD]);
  43
  44 struct ExistingName {
  45     impl_methods: BTreeMap<Symbol, Span>,
  46     trait_methods: BTreeMap<Symbol, Vec<Span>>,
  47 }
  48
  49 impl<'tcx> LateLintPass<'tcx> for SameNameMethod {
  50     fn check_crate_post(&mut self, cx: &LateContext<'tcx>) {
  51         let mut map = FxHashMap::<Res, ExistingName>::default();
  52
  53         for item in cx.tcx.hir().items() {
  54             if let ItemKind::Impl(Impl {
  55                 items,
  56                 of_trait,
  57                 self_ty,
  58                 ..
  59             }) = &item.kind
  60             {
  61                 if let TyKind::Path(QPath::Resolved(_, Path { res, .. })) = self_ty.kind {
  62                     if !map.contains_key(res) {
  63                         map.insert(
  64                             *res,
  65                             ExistingName {
  66                                 impl_methods: BTreeMap::new(),
  67                                 trait_methods: BTreeMap::new(),
  68                             },
  69                         );
  70                     }
  71                     let existing_name = map.get_mut(res).unwrap();
  72
  73                     match of_trait {
  74                         Some(trait_ref) => {
  75                             let mut methods_in_trait: BTreeSet<Symbol> = if_chain! {
  76                                 if let Some(Node::TraitRef(TraitRef { path, .. })) =
  77                                     cx.tcx.hir().find(trait_ref.hir_ref_id);
  78                                 if let Res::Def(DefKind::Trait, did) = path.res;
  79                                 then{
  80                                     // FIXME: if
  81                                     // `rustc_middle::ty::assoc::AssocItems::items` is public,
  82                                     // we can iterate its keys instead of `in_definition_order`,
  83                                     // which's more efficient
  84                                     cx.tcx
  85                                         .associated_items(did)
  86                                         .in_definition_order()
  87                                         .filter(|assoc_item| {
  88                                             matches!(assoc_item.kind, AssocKind::Fn)
  89                                         })
  90                                         .map(|assoc_item| assoc_item.name)
  91                                         .collect()
  92                                 }else{
  93                                     BTreeSet::new()
  94                                 }
  95                             };
  96
  97                             let mut check_trait_method = |method_name: Symbol, trait_method_span: Span| {
  98                                 if let Some(impl_span) = existing_name.impl_methods.get(&method_name) {
  99                                     span_lint_and_then(
 100                                         cx,
 101                                         SAME_NAME_METHOD,
 102                                         *impl_span,
 103                                         "method's name is the same as an existing method in a trait",
 104                                         |diag| {
 105                                             diag.span_note(
 106                                                 trait_method_span,
 107                                                 &format!("existing `{}` defined here", method_name),
 108                                             );
 109                                         },
 110                                     );
 111                                 }
 112                                 if let Some(v) = existing_name.trait_methods.get_mut(&method_name) {
 113                                     v.push(trait_method_span);
 114                                 } else {
 115                                     existing_name.trait_methods.insert(method_name, vec![trait_method_span]);
 116                                 }
 117                             };
 118
 119                             for impl_item_ref in (*items).iter().filter(|impl_item_ref| {
 120                                 matches!(impl_item_ref.kind, rustc_hir::AssocItemKind::Fn { .. })
 121                             }) {
 122                                 let method_name = impl_item_ref.ident.name;
 123                                 methods_in_trait.remove(&method_name);
 124                                 check_trait_method(method_name, impl_item_ref.span);
 125                             }
 126
 127                             for method_name in methods_in_trait {
 128                                 check_trait_method(method_name, item.span);
 129                             }
 130                         },
 131                         None => {
 132                             for impl_item_ref in (*items).iter().filter(|impl_item_ref| {
 133                                 matches!(impl_item_ref.kind, rustc_hir::AssocItemKind::Fn { .. })
 134                             }) {
 135                                 let method_name = impl_item_ref.ident.name;
 136                                 let impl_span = impl_item_ref.span;
 137                                 if let Some(trait_spans) = existing_name.trait_methods.get(&method_name) {
 138                                     span_lint_and_then(
 139                                         cx,
 140                                         SAME_NAME_METHOD,
 141                                         impl_span,
 142                                         "method's name is the same as an existing method in a trait",
 143                                         |diag| {
 144                                             // TODO should we `span_note` on every trait?
 145                                             // iterate on trait_spans?
 146                                             diag.span_note(
 147                                                 trait_spans[0],
 148                                                 &format!("existing `{}` defined here", method_name),
 149                                             );
 150                                         },
 151                                     );
 152                                 }
 153                                 existing_name.impl_methods.insert(method_name, impl_span);
 154                             }
 155                         },
 156                     }
 157                 }
 158             }
 159         }
 160     }
 161 }