1 //! lint on inherent implementations
3 use clippy_utils
::diagnostics
::span_lint_and_note
;
4 use clippy_utils
::{in_macro, is_allowed}
;
5 use rustc_data_structures
::fx
::FxHashMap
;
6 use rustc_hir
::{def_id::LocalDefId, Crate, 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
! {
13 /// **What it does:** Checks for multiple inherent implementations of a struct
15 /// **Why is this bad?** Splitting the implementation of a type makes the code harder to navigate.
17 /// **Known problems:** None.
39 pub MULTIPLE_INHERENT_IMPL
,
41 "Multiple inherent impl that could be grouped"
44 declare_lint_pass
!(MultipleInherentImpl
=> [MULTIPLE_INHERENT_IMPL
]);
46 impl<'tcx
> LateLintPass
<'tcx
> for MultipleInherentImpl
{
47 fn check_crate_post(&mut self, cx
: &LateContext
<'tcx
>, _
: &'tcx Crate
<'_
>) {
48 // Map from a type to it's first impl block. Needed to distinguish generic arguments.
49 // e.g. `Foo<Bar>` and `Foo<Baz>`
50 let mut type_map
= FxHashMap
::default();
51 // List of spans to lint. (lint_span, first_span)
52 let mut lint_spans
= Vec
::new();
54 for (_
, impl_ids
) in cx
56 .crate_inherent_impls(())
59 .filter(|(&id
, impls
)| {
61 // Check for `#[allow]` on the type definition
64 MULTIPLE_INHERENT_IMPL
,
65 cx
.tcx
.hir().local_def_id_to_hir_id(id
),
69 for impl_id
in impl_ids
.iter().map(|id
| id
.expect_local()) {
70 match type_map
.entry(cx
.tcx
.type_of(impl_id
)) {
72 // Store the id for the first impl block of this type. The span is retrieved lazily.
73 e
.insert(IdOrSpan
::Id(impl_id
));
75 Entry
::Occupied(mut e
) => {
76 if let Some(span
) = get_impl_span(cx
, impl_id
) {
77 let first_span
= match *e
.get() {
78 IdOrSpan
::Span(s
) => s
,
80 if let Some(s
) = get_impl_span(cx
, id
) {
81 // Remember the span of the first block.
82 *e
.get_mut() = IdOrSpan
::Span(s
);
85 // The first impl block isn't considered by the lint. Replace it with the
87 *e
.get_mut() = IdOrSpan
::Span(span
);
92 lint_spans
.push((span
, first_span
));
98 // Switching to the next type definition, no need to keep the current entries around.
102 // `TyCtxt::crate_inherent_impls` doesn't have a defined order. Sort the lint output first.
103 lint_spans
.sort_by_key(|x
| x
.0.lo());
104 for (span
, first_span
) in lint_spans
{
107 MULTIPLE_INHERENT_IMPL
,
109 "multiple implementations of this structure",
111 "first implementation here",
117 /// Gets the span for the given impl block unless it's not being considered by the lint.
118 fn get_impl_span(cx
: &LateContext
<'_
>, id
: LocalDefId
) -> Option
<Span
> {
119 let id
= cx
.tcx
.hir().local_def_id_to_hir_id(id
);
120 if let Node
::Item(&Item
{
121 kind
: ItemKind
::Impl(ref impl_item
),
124 }) = cx
.tcx
.hir().get(id
)
126 (!in_macro(span
) && impl_item
.generics
.params
.is_empty() && !is_allowed(cx
, MULTIPLE_INHERENT_IMPL
, id
))