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