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1 | //! lint on inherent implementations |
2 | ||
3 | use crate::utils::{in_macro, span_lint_and_then}; | |
4 | use rustc_data_structures::fx::FxHashMap; | |
5 | use rustc_hir::{def_id, Crate, Impl, Item, ItemKind}; | |
6 | use rustc_lint::{LateContext, LateLintPass}; | |
7 | use rustc_session::{declare_tool_lint, impl_lint_pass}; | |
8 | use rustc_span::Span; | |
9 | ||
10 | declare_clippy_lint! { | |
11 | /// **What it does:** Checks for multiple inherent implementations of a struct | |
12 | /// | |
13 | /// **Why is this bad?** Splitting the implementation of a type makes the code harder to navigate. | |
14 | /// | |
15 | /// **Known problems:** None. | |
16 | /// | |
17 | /// **Example:** | |
18 | /// ```rust | |
19 | /// struct X; | |
20 | /// impl X { | |
21 | /// fn one() {} | |
22 | /// } | |
23 | /// impl X { | |
24 | /// fn other() {} | |
25 | /// } | |
26 | /// ``` | |
27 | /// | |
28 | /// Could be written: | |
29 | /// | |
30 | /// ```rust | |
31 | /// struct X; | |
32 | /// impl X { | |
33 | /// fn one() {} | |
34 | /// fn other() {} | |
35 | /// } | |
36 | /// ``` | |
37 | pub MULTIPLE_INHERENT_IMPL, | |
38 | restriction, | |
39 | "Multiple inherent impl that could be grouped" | |
40 | } | |
41 | ||
42 | #[allow(clippy::module_name_repetitions)] | |
43 | #[derive(Default)] | |
44 | pub struct MultipleInherentImpl { | |
45 | impls: FxHashMap<def_id::DefId, Span>, | |
46 | } | |
47 | ||
48 | impl_lint_pass!(MultipleInherentImpl => [MULTIPLE_INHERENT_IMPL]); | |
49 | ||
50 | impl<'tcx> LateLintPass<'tcx> for MultipleInherentImpl { | |
51 | fn check_item(&mut self, _: &LateContext<'tcx>, item: &'tcx Item<'_>) { | |
52 | if let ItemKind::Impl(Impl { | |
53 | ref generics, | |
54 | of_trait: None, | |
55 | .. | |
56 | }) = item.kind | |
57 | { | |
58 | // Remember for each inherent implementation encountered its span and generics | |
59 | // but filter out implementations that have generic params (type or lifetime) | |
60 | // or are derived from a macro | |
61 | if !in_macro(item.span) && generics.params.is_empty() { | |
62 | self.impls.insert(item.def_id.to_def_id(), item.span); | |
63 | } | |
64 | } | |
65 | } | |
66 | ||
67 | fn check_crate_post(&mut self, cx: &LateContext<'tcx>, krate: &'tcx Crate<'_>) { | |
68 | if !krate.items.is_empty() { | |
69 | // Retrieve all inherent implementations from the crate, grouped by type | |
70 | for impls in cx.tcx.crate_inherent_impls(def_id::LOCAL_CRATE).inherent_impls.values() { | |
71 | // Filter out implementations that have generic params (type or lifetime) | |
72 | let mut impl_spans = impls.iter().filter_map(|impl_def| self.impls.get(impl_def)); | |
73 | if let Some(initial_span) = impl_spans.next() { | |
74 | impl_spans.for_each(|additional_span| { | |
75 | span_lint_and_then( | |
76 | cx, | |
77 | MULTIPLE_INHERENT_IMPL, | |
78 | *additional_span, | |
79 | "multiple implementations of this structure", | |
80 | |diag| { | |
81 | diag.span_note(*initial_span, "first implementation here"); | |
82 | }, | |
83 | ) | |
84 | }) | |
85 | } | |
86 | } | |
87 | } | |
88 | } | |
89 | } |