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Auto merge of #8972 - kyoto7250:use_retain, r=llogiq
feat(new lint): new lint `manual_retain` close #8097 This PR is a new lint implementation. This lint checks if the `retain` method is available. Thank you in advance. changelog: add new ``[`manual_retain`]`` lint
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Original file line number | Diff line number | Diff line change |
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use clippy_utils::diagnostics::span_lint_and_sugg; | ||
use clippy_utils::source::snippet; | ||
use clippy_utils::ty::is_type_diagnostic_item; | ||
use clippy_utils::{get_parent_expr, match_def_path, paths, SpanlessEq}; | ||
use clippy_utils::{meets_msrv, msrvs}; | ||
use rustc_errors::Applicability; | ||
use rustc_hir as hir; | ||
use rustc_hir::def_id::DefId; | ||
use rustc_hir::ExprKind::Assign; | ||
use rustc_lint::{LateContext, LateLintPass}; | ||
use rustc_semver::RustcVersion; | ||
use rustc_session::{declare_tool_lint, impl_lint_pass}; | ||
use rustc_span::symbol::sym; | ||
|
||
const ACCEPTABLE_METHODS: [&[&str]; 4] = [ | ||
&paths::HASHSET_ITER, | ||
&paths::BTREESET_ITER, | ||
&paths::SLICE_INTO, | ||
&paths::VEC_DEQUE_ITER, | ||
]; | ||
const ACCEPTABLE_TYPES: [(rustc_span::Symbol, Option<RustcVersion>); 6] = [ | ||
(sym::BTreeSet, Some(msrvs::BTREE_SET_RETAIN)), | ||
(sym::BTreeMap, Some(msrvs::BTREE_MAP_RETAIN)), | ||
(sym::HashSet, Some(msrvs::HASH_SET_RETAIN)), | ||
(sym::HashMap, Some(msrvs::HASH_MAP_RETAIN)), | ||
(sym::Vec, None), | ||
(sym::VecDeque, None), | ||
]; | ||
|
||
declare_clippy_lint! { | ||
/// ### What it does | ||
/// Checks for code to be replaced by `.retain()`. | ||
/// ### Why is this bad? | ||
/// `.retain()` is simpler and avoids needless allocation. | ||
/// ### Example | ||
/// ```rust | ||
/// let mut vec = vec![0, 1, 2]; | ||
/// vec = vec.iter().filter(|&x| x % 2 == 0).copied().collect(); | ||
/// vec = vec.into_iter().filter(|x| x % 2 == 0).collect(); | ||
/// ``` | ||
/// Use instead: | ||
/// ```rust | ||
/// let mut vec = vec![0, 1, 2]; | ||
/// vec.retain(|x| x % 2 == 0); | ||
/// ``` | ||
#[clippy::version = "1.63.0"] | ||
pub MANUAL_RETAIN, | ||
perf, | ||
"`retain()` is simpler and the same functionalitys" | ||
} | ||
|
||
pub struct ManualRetain { | ||
msrv: Option<RustcVersion>, | ||
} | ||
|
||
impl ManualRetain { | ||
#[must_use] | ||
pub fn new(msrv: Option<RustcVersion>) -> Self { | ||
Self { msrv } | ||
} | ||
} | ||
|
||
impl_lint_pass!(ManualRetain => [MANUAL_RETAIN]); | ||
|
||
impl<'tcx> LateLintPass<'tcx> for ManualRetain { | ||
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) { | ||
if let Some(parent_expr) = get_parent_expr(cx, expr) | ||
&& let Assign(left_expr, collect_expr, _) = &parent_expr.kind | ||
&& let hir::ExprKind::MethodCall(seg, _, _) = &collect_expr.kind | ||
&& seg.args.is_none() | ||
&& let hir::ExprKind::MethodCall(_, [target_expr], _) = &collect_expr.kind | ||
&& let Some(collect_def_id) = cx.typeck_results().type_dependent_def_id(collect_expr.hir_id) | ||
&& match_def_path(cx, collect_def_id, &paths::CORE_ITER_COLLECT) { | ||
check_into_iter(cx, parent_expr, left_expr, target_expr, self.msrv); | ||
check_iter(cx, parent_expr, left_expr, target_expr, self.msrv); | ||
check_to_owned(cx, parent_expr, left_expr, target_expr, self.msrv); | ||
} | ||
} | ||
|
||
extract_msrv_attr!(LateContext); | ||
} | ||
|
||
fn check_into_iter( | ||
cx: &LateContext<'_>, | ||
parent_expr: &hir::Expr<'_>, | ||
left_expr: &hir::Expr<'_>, | ||
target_expr: &hir::Expr<'_>, | ||
msrv: Option<RustcVersion>, | ||
) { | ||
if let hir::ExprKind::MethodCall(_, [into_iter_expr, _], _) = &target_expr.kind | ||
&& let Some(filter_def_id) = cx.typeck_results().type_dependent_def_id(target_expr.hir_id) | ||
&& match_def_path(cx, filter_def_id, &paths::CORE_ITER_FILTER) | ||
&& let hir::ExprKind::MethodCall(_, [struct_expr], _) = &into_iter_expr.kind | ||
&& let Some(into_iter_def_id) = cx.typeck_results().type_dependent_def_id(into_iter_expr.hir_id) | ||
&& match_def_path(cx, into_iter_def_id, &paths::CORE_ITER_INTO_ITER) | ||
&& match_acceptable_type(cx, left_expr, msrv) | ||
&& SpanlessEq::new(cx).eq_expr(left_expr, struct_expr) { | ||
suggest(cx, parent_expr, left_expr, target_expr); | ||
} | ||
} | ||
|
||
fn check_iter( | ||
cx: &LateContext<'_>, | ||
parent_expr: &hir::Expr<'_>, | ||
left_expr: &hir::Expr<'_>, | ||
target_expr: &hir::Expr<'_>, | ||
msrv: Option<RustcVersion>, | ||
) { | ||
if let hir::ExprKind::MethodCall(_, [filter_expr], _) = &target_expr.kind | ||
&& let Some(copied_def_id) = cx.typeck_results().type_dependent_def_id(target_expr.hir_id) | ||
&& (match_def_path(cx, copied_def_id, &paths::CORE_ITER_COPIED) | ||
|| match_def_path(cx, copied_def_id, &paths::CORE_ITER_CLONED)) | ||
&& let hir::ExprKind::MethodCall(_, [iter_expr, _], _) = &filter_expr.kind | ||
&& let Some(filter_def_id) = cx.typeck_results().type_dependent_def_id(filter_expr.hir_id) | ||
&& match_def_path(cx, filter_def_id, &paths::CORE_ITER_FILTER) | ||
&& let hir::ExprKind::MethodCall(_, [struct_expr], _) = &iter_expr.kind | ||
&& let Some(iter_expr_def_id) = cx.typeck_results().type_dependent_def_id(iter_expr.hir_id) | ||
&& match_acceptable_def_path(cx, iter_expr_def_id) | ||
&& match_acceptable_type(cx, left_expr, msrv) | ||
&& SpanlessEq::new(cx).eq_expr(left_expr, struct_expr) { | ||
suggest(cx, parent_expr, left_expr, filter_expr); | ||
} | ||
} | ||
|
||
fn check_to_owned( | ||
cx: &LateContext<'_>, | ||
parent_expr: &hir::Expr<'_>, | ||
left_expr: &hir::Expr<'_>, | ||
target_expr: &hir::Expr<'_>, | ||
msrv: Option<RustcVersion>, | ||
) { | ||
if meets_msrv(msrv, msrvs::STRING_RETAIN) | ||
&& let hir::ExprKind::MethodCall(_, [filter_expr], _) = &target_expr.kind | ||
&& let Some(to_owned_def_id) = cx.typeck_results().type_dependent_def_id(target_expr.hir_id) | ||
&& match_def_path(cx, to_owned_def_id, &paths::TO_OWNED_METHOD) | ||
&& let hir::ExprKind::MethodCall(_, [chars_expr, _], _) = &filter_expr.kind | ||
&& let Some(filter_def_id) = cx.typeck_results().type_dependent_def_id(filter_expr.hir_id) | ||
&& match_def_path(cx, filter_def_id, &paths::CORE_ITER_FILTER) | ||
&& let hir::ExprKind::MethodCall(_, [str_expr], _) = &chars_expr.kind | ||
&& let Some(chars_expr_def_id) = cx.typeck_results().type_dependent_def_id(chars_expr.hir_id) | ||
&& match_def_path(cx, chars_expr_def_id, &paths::STR_CHARS) | ||
&& let ty = cx.typeck_results().expr_ty(str_expr).peel_refs() | ||
&& is_type_diagnostic_item(cx, ty, sym::String) | ||
&& SpanlessEq::new(cx).eq_expr(left_expr, str_expr) { | ||
suggest(cx, parent_expr, left_expr, filter_expr); | ||
} | ||
} | ||
|
||
fn suggest(cx: &LateContext<'_>, parent_expr: &hir::Expr<'_>, left_expr: &hir::Expr<'_>, filter_expr: &hir::Expr<'_>) { | ||
if let hir::ExprKind::MethodCall(_, [_, closure], _) = filter_expr.kind | ||
&& let hir::ExprKind::Closure{ body, ..} = closure.kind | ||
&& let filter_body = cx.tcx.hir().body(body) | ||
&& let [filter_params] = filter_body.params | ||
&& let Some(sugg) = match filter_params.pat.kind { | ||
hir::PatKind::Binding(_, _, filter_param_ident, None) => { | ||
Some(format!("{}.retain(|{}| {})", snippet(cx, left_expr.span, ".."), filter_param_ident, snippet(cx, filter_body.value.span, ".."))) | ||
}, | ||
hir::PatKind::Tuple([key_pat, value_pat], _) => { | ||
make_sugg(cx, key_pat, value_pat, left_expr, filter_body) | ||
}, | ||
hir::PatKind::Ref(pat, _) => { | ||
match pat.kind { | ||
hir::PatKind::Binding(_, _, filter_param_ident, None) => { | ||
Some(format!("{}.retain(|{}| {})", snippet(cx, left_expr.span, ".."), filter_param_ident, snippet(cx, filter_body.value.span, ".."))) | ||
}, | ||
_ => None | ||
} | ||
}, | ||
_ => None | ||
} { | ||
span_lint_and_sugg( | ||
cx, | ||
MANUAL_RETAIN, | ||
parent_expr.span, | ||
"this expression can be written more simply using `.retain()`", | ||
"consider calling `.retain()` instead", | ||
sugg, | ||
Applicability::MachineApplicable | ||
); | ||
} | ||
} | ||
|
||
fn make_sugg( | ||
cx: &LateContext<'_>, | ||
key_pat: &rustc_hir::Pat<'_>, | ||
value_pat: &rustc_hir::Pat<'_>, | ||
left_expr: &hir::Expr<'_>, | ||
filter_body: &hir::Body<'_>, | ||
) -> Option<String> { | ||
match (&key_pat.kind, &value_pat.kind) { | ||
(hir::PatKind::Binding(_, _, key_param_ident, None), hir::PatKind::Binding(_, _, value_param_ident, None)) => { | ||
Some(format!( | ||
"{}.retain(|{}, &mut {}| {})", | ||
snippet(cx, left_expr.span, ".."), | ||
key_param_ident, | ||
value_param_ident, | ||
snippet(cx, filter_body.value.span, "..") | ||
)) | ||
}, | ||
(hir::PatKind::Binding(_, _, key_param_ident, None), hir::PatKind::Wild) => Some(format!( | ||
"{}.retain(|{}, _| {})", | ||
snippet(cx, left_expr.span, ".."), | ||
key_param_ident, | ||
snippet(cx, filter_body.value.span, "..") | ||
)), | ||
(hir::PatKind::Wild, hir::PatKind::Binding(_, _, value_param_ident, None)) => Some(format!( | ||
"{}.retain(|_, &mut {}| {})", | ||
snippet(cx, left_expr.span, ".."), | ||
value_param_ident, | ||
snippet(cx, filter_body.value.span, "..") | ||
)), | ||
_ => None, | ||
} | ||
} | ||
|
||
fn match_acceptable_def_path(cx: &LateContext<'_>, collect_def_id: DefId) -> bool { | ||
ACCEPTABLE_METHODS | ||
.iter() | ||
.any(|&method| match_def_path(cx, collect_def_id, method)) | ||
} | ||
|
||
fn match_acceptable_type(cx: &LateContext<'_>, expr: &hir::Expr<'_>, msrv: Option<RustcVersion>) -> bool { | ||
let expr_ty = cx.typeck_results().expr_ty(expr).peel_refs(); | ||
ACCEPTABLE_TYPES.iter().any(|(ty, acceptable_msrv)| { | ||
is_type_diagnostic_item(cx, expr_ty, *ty) | ||
&& acceptable_msrv.map_or(true, |acceptable_msrv| meets_msrv(msrv, acceptable_msrv)) | ||
}) | ||
} |
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