1 //! lint on inherent implementations
3 use clippy_utils::diagnostics::span_lint_and_then;
4 use clippy_utils::in_macro;
5 use rustc_hir::def_id::DefIdMap;
6 use rustc_hir::{def_id, Crate, Impl, Item, ItemKind};
7 use rustc_lint::{LateContext, LateLintPass};
8 use rustc_session::{declare_tool_lint, impl_lint_pass};
11 declare_clippy_lint! {
12 /// **What it does:** Checks for multiple inherent implementations of a struct
14 /// **Why is this bad?** Splitting the implementation of a type makes the code harder to navigate.
16 /// **Known problems:** None.
38 pub MULTIPLE_INHERENT_IMPL,
40 "Multiple inherent impl that could be grouped"
43 #[allow(clippy::module_name_repetitions)]
45 pub struct MultipleInherentImpl {
46 impls: DefIdMap<Span>,
49 impl_lint_pass!(MultipleInherentImpl => [MULTIPLE_INHERENT_IMPL]);
51 impl<'tcx> LateLintPass<'tcx> for MultipleInherentImpl {
52 fn check_item(&mut self, _: &LateContext<'tcx>, item: &'tcx Item<'_>) {
53 if let ItemKind::Impl(Impl {
59 // Remember for each inherent implementation encountered its span and generics
60 // but filter out implementations that have generic params (type or lifetime)
61 // or are derived from a macro
62 if !in_macro(item.span) && generics.params.is_empty() {
63 self.impls.insert(item.def_id.to_def_id(), item.span);
68 fn check_crate_post(&mut self, cx: &LateContext<'tcx>, krate: &'tcx Crate<'_>) {
69 if !krate.items.is_empty() {
70 // Retrieve all inherent implementations from the crate, grouped by type
71 for impls in cx.tcx.crate_inherent_impls(def_id::LOCAL_CRATE).inherent_impls.values() {
72 // Filter out implementations that have generic params (type or lifetime)
73 let mut impl_spans = impls.iter().filter_map(|impl_def| self.impls.get(impl_def));
74 if let Some(initial_span) = impl_spans.next() {
75 impl_spans.for_each(|additional_span| {
78 MULTIPLE_INHERENT_IMPL,
80 "multiple implementations of this structure",
82 diag.span_note(*initial_span, "first implementation here");