1 //! lint on inherent implementations
3 use clippy_utils::diagnostics::span_lint_and_note;
4 use clippy_utils::is_lint_allowed;
5 use rustc_data_structures::fx::FxHashMap;
6 use rustc_hir::{def_id::LocalDefId, Item, ItemKind, Node};
7 use rustc_lint::{LateContext, LateLintPass};
8 use rustc_session::{declare_lint_pass, declare_tool_lint};
10 use std::collections::hash_map::Entry;
12 declare_clippy_lint! {
14 /// Checks for multiple inherent implementations of a struct
16 /// ### Why is this bad?
17 /// Splitting the implementation of a type makes the code harder to navigate.
39 #[clippy::version = "pre 1.29.0"]
40 pub MULTIPLE_INHERENT_IMPL,
42 "Multiple inherent impl that could be grouped"
45 declare_lint_pass!(MultipleInherentImpl => [MULTIPLE_INHERENT_IMPL]);
47 impl<'tcx> LateLintPass<'tcx> for MultipleInherentImpl {
48 fn check_crate_post(&mut self, cx: &LateContext<'tcx>) {
49 // Map from a type to it's first impl block. Needed to distinguish generic arguments.
50 // e.g. `Foo<Bar>` and `Foo<Baz>`
51 let mut type_map = FxHashMap::default();
52 // List of spans to lint. (lint_span, first_span)
53 let mut lint_spans = Vec::new();
55 for (_, impl_ids) in cx
57 .crate_inherent_impls(())
60 .filter(|(&id, impls)| {
62 // Check for `#[allow]` on the type definition
65 MULTIPLE_INHERENT_IMPL,
66 cx.tcx.hir().local_def_id_to_hir_id(id),
70 for impl_id in impl_ids.iter().map(|id| id.expect_local()) {
71 match type_map.entry(cx.tcx.type_of(impl_id)) {
73 // Store the id for the first impl block of this type. The span is retrieved lazily.
74 e.insert(IdOrSpan::Id(impl_id));
76 Entry::Occupied(mut e) => {
77 if let Some(span) = get_impl_span(cx, impl_id) {
78 let first_span = match *e.get() {
79 IdOrSpan::Span(s) => s,
81 if let Some(s) = get_impl_span(cx, id) {
82 // Remember the span of the first block.
83 *e.get_mut() = IdOrSpan::Span(s);
86 // The first impl block isn't considered by the lint. Replace it with the
88 *e.get_mut() = IdOrSpan::Span(span);
93 lint_spans.push((span, first_span));
99 // Switching to the next type definition, no need to keep the current entries around.
103 // `TyCtxt::crate_inherent_impls` doesn't have a defined order. Sort the lint output first.
104 lint_spans.sort_by_key(|x| x.0.lo());
105 for (span, first_span) in lint_spans {
108 MULTIPLE_INHERENT_IMPL,
110 "multiple implementations of this structure",
112 "first implementation here",
118 /// Gets the span for the given impl block unless it's not being considered by the lint.
119 fn get_impl_span(cx: &LateContext<'_>, id: LocalDefId) -> Option<Span> {
120 let id = cx.tcx.hir().local_def_id_to_hir_id(id);
121 if let Node::Item(&Item {
122 kind: ItemKind::Impl(ref impl_item),
125 }) = cx.tcx.hir().get(id)
127 (!span.from_expansion()
128 && impl_item.generics.params.is_empty()
129 && !is_lint_allowed(cx, MULTIPLE_INHERENT_IMPL, id))