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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(&hir::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))
})
}
|
