src/tools/clippy/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 id in cx.tcx.hir().items() {
  54             if !matches!(cx.tcx.hir().def_kind(id.def_id), DefKind::Impl) {
  55                 continue;
  56             }
  57
  58             let item = cx.tcx.hir().item(id);
  59             if let ItemKind::Impl(Impl {
  60                 items,
  61                 of_trait,
  62                 self_ty,
  63                 ..
  64             }) = &item.kind
  65             {
  66                 if let TyKind::Path(QPath::Resolved(_, Path { res, .. })) = self_ty.kind {
  67                     if !map.contains_key(res) {
  68                         map.insert(
  69                             *res,
  70                             ExistingName {
  71                                 impl_methods: BTreeMap::new(),
  72                                 trait_methods: BTreeMap::new(),
  73                             },
  74                         );
  75                     }
  76                     let existing_name = map.get_mut(res).unwrap();
  77
  78                     match of_trait {
  79                         Some(trait_ref) => {
  80                             let mut methods_in_trait: BTreeSet<Symbol> = if_chain! {
  81                                 if let Some(Node::TraitRef(TraitRef { path, .. })) =
  82                                     cx.tcx.hir().find(trait_ref.hir_ref_id);
  83                                 if let Res::Def(DefKind::Trait, did) = path.res;
  84                                 then{
  85                                     // FIXME: if
  86                                     // `rustc_middle::ty::assoc::AssocItems::items` is public,
  87                                     // we can iterate its keys instead of `in_definition_order`,
  88                                     // which's more efficient
  89                                     cx.tcx
  90                                         .associated_items(did)
  91                                         .in_definition_order()
  92                                         .filter(|assoc_item| {
  93                                             matches!(assoc_item.kind, AssocKind::Fn)
  94                                         })
  95                                         .map(|assoc_item| assoc_item.name)
  96                                         .collect()
  97                                 }else{
  98                                     BTreeSet::new()
  99                                 }
 100                             };
 101
 102                             let mut check_trait_method = |method_name: Symbol, trait_method_span: Span| {
 103                                 if let Some(impl_span) = existing_name.impl_methods.get(&method_name) {
 104                                     span_lint_and_then(
 105                                         cx,
 106                                         SAME_NAME_METHOD,
 107                                         *impl_span,
 108                                         "method's name is the same as an existing method in a trait",
 109                                         |diag| {
 110                                             diag.span_note(
 111                                                 trait_method_span,
 112                                                 &format!("existing `{}` defined here", method_name),
 113                                             );
 114                                         },
 115                                     );
 116                                 }
 117                                 if let Some(v) = existing_name.trait_methods.get_mut(&method_name) {
 118                                     v.push(trait_method_span);
 119                                 } else {
 120                                     existing_name.trait_methods.insert(method_name, vec![trait_method_span]);
 121                                 }
 122                             };
 123
 124                             for impl_item_ref in (*items).iter().filter(|impl_item_ref| {
 125                                 matches!(impl_item_ref.kind, rustc_hir::AssocItemKind::Fn { .. })
 126                             }) {
 127                                 let method_name = impl_item_ref.ident.name;
 128                                 methods_in_trait.remove(&method_name);
 129                                 check_trait_method(method_name, impl_item_ref.span);
 130                             }
 131
 132                             for method_name in methods_in_trait {
 133                                 check_trait_method(method_name, item.span);
 134                             }
 135                         },
 136                         None => {
 137                             for impl_item_ref in (*items).iter().filter(|impl_item_ref| {
 138                                 matches!(impl_item_ref.kind, rustc_hir::AssocItemKind::Fn { .. })
 139                             }) {
 140                                 let method_name = impl_item_ref.ident.name;
 141                                 let impl_span = impl_item_ref.span;
 142                                 if let Some(trait_spans) = existing_name.trait_methods.get(&method_name) {
 143                                     span_lint_and_then(
 144                                         cx,
 145                                         SAME_NAME_METHOD,
 146                                         impl_span,
 147                                         "method's name is the same as an existing method in a trait",
 148                                         |diag| {
 149                                             // TODO should we `span_note` on every trait?
 150                                             // iterate on trait_spans?
 151                                             diag.span_note(
 152                                                 trait_spans[0],
 153                                                 &format!("existing `{}` defined here", method_name),
 154                                             );
 155                                         },
 156                                     );
 157                                 }
 158                                 existing_name.impl_methods.insert(method_name, impl_span);
 159                             }
 160                         },
 161                     }
 162                 }
 163             }
 164         }
 165     }
 166 }