1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use clippy_utils::msrvs::{self, Msrv};
3 use clippy_utils::source::snippet;
4 use clippy_utils::ty::{is_type_diagnostic_item, is_type_lang_item};
5 use clippy_utils::{get_parent_expr, match_def_path, paths, SpanlessEq};
6 use rustc_errors::Applicability;
8 use rustc_hir::def_id::DefId;
9 use rustc_hir::ExprKind::Assign;
10 use rustc_lint::{LateContext, LateLintPass};
11 use rustc_semver::RustcVersion;
12 use rustc_session::{declare_tool_lint, impl_lint_pass};
13 use rustc_span::symbol::sym;
15 const ACCEPTABLE_METHODS: [&[&str]; 4] = [
17 &paths::BTREESET_ITER,
19 &paths::VEC_DEQUE_ITER,
21 const ACCEPTABLE_TYPES: [(rustc_span::Symbol, Option<RustcVersion>); 6] = [
22 (sym::BTreeSet, Some(msrvs::BTREE_SET_RETAIN)),
23 (sym::BTreeMap, Some(msrvs::BTREE_MAP_RETAIN)),
24 (sym::HashSet, Some(msrvs::HASH_SET_RETAIN)),
25 (sym::HashMap, Some(msrvs::HASH_MAP_RETAIN)),
27 (sym::VecDeque, None),
30 declare_clippy_lint! {
32 /// Checks for code to be replaced by `.retain()`.
33 /// ### Why is this bad?
34 /// `.retain()` is simpler and avoids needless allocation.
37 /// let mut vec = vec![0, 1, 2];
38 /// vec = vec.iter().filter(|&x| x % 2 == 0).copied().collect();
39 /// vec = vec.into_iter().filter(|x| x % 2 == 0).collect();
43 /// let mut vec = vec![0, 1, 2];
44 /// vec.retain(|x| x % 2 == 0);
46 #[clippy::version = "1.64.0"]
49 "`retain()` is simpler and the same functionalitys"
52 pub struct ManualRetain {
58 pub fn new(msrv: Msrv) -> Self {
63 impl_lint_pass!(ManualRetain => [MANUAL_RETAIN]);
65 impl<'tcx> LateLintPass<'tcx> for ManualRetain {
66 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
67 if let Some(parent_expr) = get_parent_expr(cx, expr)
68 && let Assign(left_expr, collect_expr, _) = &parent_expr.kind
69 && let hir::ExprKind::MethodCall(seg, ..) = &collect_expr.kind
71 && let hir::ExprKind::MethodCall(_, target_expr, [], _) = &collect_expr.kind
72 && let Some(collect_def_id) = cx.typeck_results().type_dependent_def_id(collect_expr.hir_id)
73 && cx.tcx.is_diagnostic_item(sym::iterator_collect_fn, collect_def_id)
75 check_into_iter(cx, parent_expr, left_expr, target_expr, &self.msrv);
76 check_iter(cx, parent_expr, left_expr, target_expr, &self.msrv);
77 check_to_owned(cx, parent_expr, left_expr, target_expr, &self.msrv);
81 extract_msrv_attr!(LateContext);
86 parent_expr: &hir::Expr<'_>,
87 left_expr: &hir::Expr<'_>,
88 target_expr: &hir::Expr<'_>,
91 if let hir::ExprKind::MethodCall(_, into_iter_expr, [_], _) = &target_expr.kind
92 && let Some(filter_def_id) = cx.typeck_results().type_dependent_def_id(target_expr.hir_id)
93 && match_def_path(cx, filter_def_id, &paths::CORE_ITER_FILTER)
94 && let hir::ExprKind::MethodCall(_, struct_expr, [], _) = &into_iter_expr.kind
95 && let Some(into_iter_def_id) = cx.typeck_results().type_dependent_def_id(into_iter_expr.hir_id)
96 && Some(into_iter_def_id) == cx.tcx.lang_items().into_iter_fn()
97 && match_acceptable_type(cx, left_expr, msrv)
98 && SpanlessEq::new(cx).eq_expr(left_expr, struct_expr) {
99 suggest(cx, parent_expr, left_expr, target_expr);
104 cx: &LateContext<'_>,
105 parent_expr: &hir::Expr<'_>,
106 left_expr: &hir::Expr<'_>,
107 target_expr: &hir::Expr<'_>,
110 if let hir::ExprKind::MethodCall(_, filter_expr, [], _) = &target_expr.kind
111 && let Some(copied_def_id) = cx.typeck_results().type_dependent_def_id(target_expr.hir_id)
112 && (match_def_path(cx, copied_def_id, &paths::CORE_ITER_COPIED)
113 || match_def_path(cx, copied_def_id, &paths::CORE_ITER_CLONED))
114 && let hir::ExprKind::MethodCall(_, iter_expr, [_], _) = &filter_expr.kind
115 && let Some(filter_def_id) = cx.typeck_results().type_dependent_def_id(filter_expr.hir_id)
116 && match_def_path(cx, filter_def_id, &paths::CORE_ITER_FILTER)
117 && let hir::ExprKind::MethodCall(_, struct_expr, [], _) = &iter_expr.kind
118 && let Some(iter_expr_def_id) = cx.typeck_results().type_dependent_def_id(iter_expr.hir_id)
119 && match_acceptable_def_path(cx, iter_expr_def_id)
120 && match_acceptable_type(cx, left_expr, msrv)
121 && SpanlessEq::new(cx).eq_expr(left_expr, struct_expr) {
122 suggest(cx, parent_expr, left_expr, filter_expr);
127 cx: &LateContext<'_>,
128 parent_expr: &hir::Expr<'_>,
129 left_expr: &hir::Expr<'_>,
130 target_expr: &hir::Expr<'_>,
133 if msrv.meets(msrvs::STRING_RETAIN)
134 && let hir::ExprKind::MethodCall(_, filter_expr, [], _) = &target_expr.kind
135 && let Some(to_owned_def_id) = cx.typeck_results().type_dependent_def_id(target_expr.hir_id)
136 && match_def_path(cx, to_owned_def_id, &paths::TO_OWNED_METHOD)
137 && let hir::ExprKind::MethodCall(_, chars_expr, [_], _) = &filter_expr.kind
138 && let Some(filter_def_id) = cx.typeck_results().type_dependent_def_id(filter_expr.hir_id)
139 && match_def_path(cx, filter_def_id, &paths::CORE_ITER_FILTER)
140 && let hir::ExprKind::MethodCall(_, str_expr, [], _) = &chars_expr.kind
141 && let Some(chars_expr_def_id) = cx.typeck_results().type_dependent_def_id(chars_expr.hir_id)
142 && match_def_path(cx, chars_expr_def_id, &paths::STR_CHARS)
143 && let ty = cx.typeck_results().expr_ty(str_expr).peel_refs()
144 && is_type_lang_item(cx, ty, hir::LangItem::String)
145 && SpanlessEq::new(cx).eq_expr(left_expr, str_expr) {
146 suggest(cx, parent_expr, left_expr, filter_expr);
150 fn suggest(cx: &LateContext<'_>, parent_expr: &hir::Expr<'_>, left_expr: &hir::Expr<'_>, filter_expr: &hir::Expr<'_>) {
151 if let hir::ExprKind::MethodCall(_, _, [closure], _) = filter_expr.kind
152 && let hir::ExprKind::Closure(&hir::Closure { body, ..}) = closure.kind
153 && let filter_body = cx.tcx.hir().body(body)
154 && let [filter_params] = filter_body.params
155 && let Some(sugg) = match filter_params.pat.kind {
156 hir::PatKind::Binding(_, _, filter_param_ident, None) => {
157 Some(format!("{}.retain(|{filter_param_ident}| {})", snippet(cx, left_expr.span, ".."), snippet(cx, filter_body.value.span, "..")))
159 hir::PatKind::Tuple([key_pat, value_pat], _) => {
160 make_sugg(cx, key_pat, value_pat, left_expr, filter_body)
162 hir::PatKind::Ref(pat, _) => {
164 hir::PatKind::Binding(_, _, filter_param_ident, None) => {
165 Some(format!("{}.retain(|{filter_param_ident}| {})", snippet(cx, left_expr.span, ".."), snippet(cx, filter_body.value.span, "..")))
176 "this expression can be written more simply using `.retain()`",
177 "consider calling `.retain()` instead",
179 Applicability::MachineApplicable
185 cx: &LateContext<'_>,
186 key_pat: &rustc_hir::Pat<'_>,
187 value_pat: &rustc_hir::Pat<'_>,
188 left_expr: &hir::Expr<'_>,
189 filter_body: &hir::Body<'_>,
190 ) -> Option<String> {
191 match (&key_pat.kind, &value_pat.kind) {
192 (hir::PatKind::Binding(_, _, key_param_ident, None), hir::PatKind::Binding(_, _, value_param_ident, None)) => {
194 "{}.retain(|{key_param_ident}, &mut {value_param_ident}| {})",
195 snippet(cx, left_expr.span, ".."),
196 snippet(cx, filter_body.value.span, "..")
199 (hir::PatKind::Binding(_, _, key_param_ident, None), hir::PatKind::Wild) => Some(format!(
200 "{}.retain(|{key_param_ident}, _| {})",
201 snippet(cx, left_expr.span, ".."),
202 snippet(cx, filter_body.value.span, "..")
204 (hir::PatKind::Wild, hir::PatKind::Binding(_, _, value_param_ident, None)) => Some(format!(
205 "{}.retain(|_, &mut {value_param_ident}| {})",
206 snippet(cx, left_expr.span, ".."),
207 snippet(cx, filter_body.value.span, "..")
213 fn match_acceptable_def_path(cx: &LateContext<'_>, collect_def_id: DefId) -> bool {
216 .any(|&method| match_def_path(cx, collect_def_id, method))
219 fn match_acceptable_type(cx: &LateContext<'_>, expr: &hir::Expr<'_>, msrv: &Msrv) -> bool {
220 let expr_ty = cx.typeck_results().expr_ty(expr).peel_refs();
221 ACCEPTABLE_TYPES.iter().any(|(ty, acceptable_msrv)| {
222 is_type_diagnostic_item(cx, expr_ty, *ty)
223 && acceptable_msrv.map_or(true, |acceptable_msrv| msrv.meets(acceptable_msrv))