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[iter_overeager_cloned]: detect .cloned().map() and .cloned().for_each()

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key idea:
for `f` in `.map(f)` and `.for_each(f)`:
1. `f` must be a closure with one parameter
2. don't lint if mutable paramter in clsure `f`: `|mut x| ...`
3. don't lint if parameter is moved
This commit is contained in:
lengyijun 2023-08-05 10:20:16 +08:00
parent b7cad50eca
commit e440065a0f
5 changed files with 102 additions and 15 deletions
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77
clippy_lints/src/methods/iter_overeager_cloned.rs
View File

@ -1,14 +1,18 @@
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::source::snippet_opt;
use clippy_utils::ty::{implements_trait, is_copy};
use rustc_ast::BindingAnnotation;
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind};
use rustc_hir::{Body, Expr, ExprKind, HirId, HirIdSet, PatKind};
use rustc_hir_typeck::expr_use_visitor::{Delegate, ExprUseVisitor, PlaceBase, PlaceWithHirId};
use rustc_lint::LateContext;
use rustc_middle::ty;
use rustc_middle::mir::{FakeReadCause, Mutability};
use rustc_middle::ty::{self, BorrowKind};
use rustc_span::sym;
use super::ITER_OVEREAGER_CLONED;
use crate::redundant_clone::REDUNDANT_CLONE;
use crate::rustc_trait_selection::infer::TyCtxtInferExt;
#[derive(Clone, Copy)]
pub(super) enum Op<'a> {
@ -16,6 +20,10 @@ pub(super) enum Op<'a> {
// e.g. `count`
RmCloned,
// rm `.cloned()`
// e.g. `map` `for_each`
NeedlessMove(&'a str, &'a Expr<'a>),
// later `.cloned()`
// and add `&` to the parameter of closure parameter
// e.g. `find` `filter`
@ -51,8 +59,46 @@ pub(super) fn check<'tcx>(
return;
}
if let Op::NeedlessMove(_, expr) = op {
let rustc_hir::ExprKind::Closure(closure) = expr.kind else { return } ;
let body @ Body { params: [p], .. } = cx.tcx.hir().body(closure.body) else { return };
let mut delegate = MoveDelegate {used_move : HirIdSet::default()};
let infcx = cx.tcx.infer_ctxt().build();
ExprUseVisitor::new(
&mut delegate,
&infcx,
closure.body.hir_id.owner.def_id,
cx.param_env,
cx.typeck_results(),
)
.consume_body(body);
let mut to_be_discarded = false;
p.pat.walk(|it| {
if delegate.used_move.contains(&it.hir_id){
to_be_discarded = true;
return false;
}
match it.kind {
PatKind::Binding(BindingAnnotation(_, Mutability::Mut), _, _, _)
| PatKind::Ref(_, Mutability::Mut) => {
to_be_discarded = true;
false
}
_ => { true }
}
});
if to_be_discarded {
return;
}
}
let (lint, msg, trailing_clone) = match op {
Op::RmCloned => (REDUNDANT_CLONE, "unneeded cloning of iterator items", ""),
Op::RmCloned | Op::NeedlessMove(_, _) => (REDUNDANT_CLONE, "unneeded cloning of iterator items", ""),
Op::LaterCloned | Op::FixClosure(_, _) => (ITER_OVEREAGER_CLONED, "unnecessarily eager cloning of iterator items", ".cloned()"),
};
@ -83,8 +129,33 @@ pub(super) fn check<'tcx>(
diag.span_suggestion(replace_span, "try", snip, Applicability::MachineApplicable);
}
}
Op::NeedlessMove(_, _) => {
let method_span = expr.span.with_lo(cloned_call.span.hi());
if let Some(snip) = snippet_opt(cx, method_span) {
let replace_span = expr.span.with_lo(cloned_recv.span.hi());
diag.span_suggestion(replace_span, "try", snip, Applicability::MaybeIncorrect);
}
}
}
}
);
}
}
struct MoveDelegate {
used_move: HirIdSet,
}
impl<'tcx> Delegate<'tcx> for MoveDelegate {
fn consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, _: HirId) {
if let PlaceBase::Local(l) = place_with_id.place.base {
self.used_move.insert(l);
}
}
fn borrow(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId, _: BorrowKind) {}
fn mutate(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
fn fake_read(&mut self, _: &PlaceWithHirId<'tcx>, _: FakeReadCause, _: HirId) {}
}

14
clippy_lints/src/methods/mod.rs
View File

@ -4001,9 +4001,11 @@ fn check_methods<'tcx>(&self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
manual_try_fold::check(cx, expr, init, acc, call_span, &self.msrv);
unnecessary_fold::check(cx, expr, init, acc, span);
},
("for_each", [_]) => {
if let Some(("inspect", _, [_], span2, _)) = method_call(recv) {
inspect_for_each::check(cx, expr, span2);
("for_each", [arg]) => {
match method_call(recv) {
Some(("inspect", _, [_], span2, _)) => inspect_for_each::check(cx, expr, span2),
Some(("cloned", recv2, [], _, _)) => iter_overeager_cloned::check(cx, expr, recv, recv2, iter_overeager_cloned::Op::NeedlessMove(name, arg), false),
_ => {}
}
},
("get", [arg]) => {
@ -4038,8 +4040,10 @@ fn check_methods<'tcx>(&self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
(name @ ("map" | "map_err"), [m_arg]) => {
if name == "map" {
map_clone::check(cx, expr, recv, m_arg, &self.msrv);
if let Some((map_name @ ("iter" | "into_iter"), recv2, _, _, _)) = method_call(recv) {
iter_kv_map::check(cx, map_name, expr, recv2, m_arg);
match method_call(recv) {
Some((map_name @ ("iter" | "into_iter"), recv2, _, _, _)) => iter_kv_map::check(cx, map_name, expr, recv2, m_arg),
Some(("cloned", recv2, [], _, _)) => iter_overeager_cloned::check(cx, expr, recv, recv2, iter_overeager_cloned::Op::NeedlessMove(name, m_arg), false),
_ => {}
}
} else {
map_err_ignore::check(cx, expr, m_arg);

6
tests/ui/iter_overeager_cloned.fixed
View File

@ -56,14 +56,12 @@ fn main() {
}
}
// Not implemented yet
let _ = vec.iter().cloned().map(|x| x.len());
let _ = vec.iter().map(|x| x.len());
// This would fail if changed.
let _ = vec.iter().cloned().map(|x| x + "2");
// Not implemented yet
let _ = vec.iter().cloned().for_each(|x| assert!(!x.is_empty()));
let _ = vec.iter().for_each(|x| assert!(!x.is_empty()));
// Not implemented yet
let _ = vec.iter().cloned().all(|x| x.len() == 1);

2
tests/ui/iter_overeager_cloned.rs
View File

@ -57,13 +57,11 @@ fn bar<'a>(iter: impl Iterator<Item = &'a S<'a>> + 'a, target: String) -> impl I
}
}
// Not implemented yet
let _ = vec.iter().cloned().map(|x| x.len());
// This would fail if changed.
let _ = vec.iter().cloned().map(|x| x + "2");
// Not implemented yet
let _ = vec.iter().cloned().for_each(|x| assert!(!x.is_empty()));
// Not implemented yet

18
tests/ui/iter_overeager_cloned.stderr
View File

@ -130,5 +130,21 @@ LL | iter.cloned().filter(move |S { a, b }| **a == 1 && b == &target
| |
| help: try: `.filter(move |&S { a, b }| **a == 1 && b == &target).cloned()`
error: aborting due to 15 previous errors
error: unneeded cloning of iterator items
--> $DIR/iter_overeager_cloned.rs:60:13
|
LL | let _ = vec.iter().cloned().map(|x| x.len());
| ^^^^^^^^^^--------------------------
| |
| help: try: `.map(|x| x.len())`
error: unneeded cloning of iterator items
--> $DIR/iter_overeager_cloned.rs:65:13
|
LL | let _ = vec.iter().cloned().for_each(|x| assert!(!x.is_empty()));
| ^^^^^^^^^^----------------------------------------------
| |
| help: try: `.for_each(|x| assert!(!x.is_empty()))`
error: aborting due to 17 previous errors