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J-ZhengLiJ-ZhengLi
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implement unoptimized code logic for [infinite_loops]
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‎CHANGELOG.md

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Original file line numberDiff line numberDiff line change
@@ -5147,6 +5147,7 @@ Released 2018-09-13
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[`inefficient_to_string`]: https://rust-lang.github.io/rust-clippy/master/index.html#inefficient_to_string
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[`infallible_destructuring_match`]: https://rust-lang.github.io/rust-clippy/master/index.html#infallible_destructuring_match
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[`infinite_iter`]: https://rust-lang.github.io/rust-clippy/master/index.html#infinite_iter
5150+
[`infinite_loops`]: https://rust-lang.github.io/rust-clippy/master/index.html#infinite_loops
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[`inherent_to_string`]: https://rust-lang.github.io/rust-clippy/master/index.html#inherent_to_string
51515152
[`inherent_to_string_shadow_display`]: https://rust-lang.github.io/rust-clippy/master/index.html#inherent_to_string_shadow_display
51525153
[`init_numbered_fields`]: https://rust-lang.github.io/rust-clippy/master/index.html#init_numbered_fields

‎clippy_lints/src/declared_lints.rs

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Original file line numberDiff line numberDiff line change
@@ -263,6 +263,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
263263
crate::loops::EXPLICIT_INTO_ITER_LOOP_INFO,
264264
crate::loops::EXPLICIT_ITER_LOOP_INFO,
265265
crate::loops::FOR_KV_MAP_INFO,
266+
crate::loops::INFINITE_LOOPS_INFO,
266267
crate::loops::ITER_NEXT_LOOP_INFO,
267268
crate::loops::MANUAL_FIND_INFO,
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crate::loops::MANUAL_FLATTEN_INFO,

‎clippy_lints/src/loops/infinite_loops.rs

+92
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,92 @@
1+
use clippy_utils::diagnostics::span_lint_and_then;
2+
use clippy_utils::is_lint_allowed;
3+
use hir::intravisit::{walk_expr, Visitor};
4+
use hir::{Block, Destination, Expr, ExprKind, FnRetTy, Ty, TyKind};
5+
use rustc_ast::Label;
6+
use rustc_errors::Applicability;
7+
use rustc_hir as hir;
8+
use rustc_lint::LateContext;
9+
10+
use super::INFINITE_LOOPS;
11+
12+
pub(super) fn check(
13+
cx: &LateContext<'_>,
14+
expr: &Expr<'_>,
15+
loop_block: &Block<'_>,
16+
label: Option<Label>,
17+
parent_fn_ret_ty: FnRetTy<'_>,
18+
) {
19+
if is_lint_allowed(cx, INFINITE_LOOPS, expr.hir_id)
20+
|| matches!(
21+
parent_fn_ret_ty,
22+
FnRetTy::Return(Ty {
23+
kind: TyKind::Never,
24+
..
25+
})
26+
)
27+
{
28+
return;
29+
}
30+
31+
// First, find any `break` or `return` without entering any inner loop,
32+
// then, find `return` or labeled `break` which breaks this loop with entering inner loop,
33+
// otherwise this loop is a infinite loop.
34+
let mut direct_br_or_ret_finder = BreakOrRetFinder::default();
35+
direct_br_or_ret_finder.visit_block(loop_block);
36+
37+
let is_finite_loop = direct_br_or_ret_finder.found || {
38+
let mut inner_br_or_ret_finder = BreakOrRetFinder {
39+
label,
40+
enter_nested_loop: true,
41+
..Default::default()
42+
};
43+
inner_br_or_ret_finder.visit_block(loop_block);
44+
inner_br_or_ret_finder.found
45+
};
46+
47+
if !is_finite_loop {
48+
span_lint_and_then(cx, INFINITE_LOOPS, expr.span, "infinite loop detected", |diag| {
49+
if let FnRetTy::DefaultReturn(ret_span) = parent_fn_ret_ty {
50+
diag.span_suggestion(
51+
ret_span,
52+
"if this is intentional, consider specifing `!` as function return",
53+
" -> !",
54+
Applicability::MaybeIncorrect,
55+
);
56+
} else {
57+
diag.span_help(
58+
expr.span,
59+
"if this is not intended, add a `break` or `return` condition in this loop",
60+
);
61+
}
62+
});
63+
}
64+
}
65+
66+
#[derive(Default)]
67+
struct BreakOrRetFinder {
68+
label: Option<Label>,
69+
found: bool,
70+
enter_nested_loop: bool,
71+
}
72+
73+
impl<'hir> Visitor<'hir> for BreakOrRetFinder {
74+
fn visit_expr(&mut self, ex: &'hir Expr<'_>) {
75+
match &ex.kind {
76+
ExprKind::Break(Destination { label, .. }, ..) => {
77+
// When entering nested loop, only by breaking this loop's label
78+
// would be considered as exiting this loop.
79+
if self.enter_nested_loop {
80+
if label.is_some() && *label == self.label {
81+
self.found = true;
82+
}
83+
} else {
84+
self.found = true;
85+
}
86+
},
87+
ExprKind::Ret(..) => self.found = true,
88+
ExprKind::Loop(..) if !self.enter_nested_loop => (),
89+
_ => walk_expr(self, ex),
90+
}
91+
}
92+
}

‎clippy_lints/src/loops/mod.rs

+71-8
Original file line numberDiff line numberDiff line change
@@ -3,6 +3,7 @@ mod explicit_counter_loop;
33
mod explicit_into_iter_loop;
44
mod explicit_iter_loop;
55
mod for_kv_map;
6+
mod infinite_loops;
67
mod iter_next_loop;
78
mod manual_find;
89
mod manual_flatten;
@@ -22,7 +23,7 @@ mod while_let_on_iterator;
2223

2324
use clippy_config::msrvs::Msrv;
2425
use clippy_utils::higher;
25-
use rustc_hir::{Expr, ExprKind, LoopSource, Pat};
26+
use rustc_hir::{self as hir, Expr, ExprKind, LoopSource, Pat};
2627
use rustc_lint::{LateContext, LateLintPass};
2728
use rustc_session::{declare_tool_lint, impl_lint_pass};
2829
use rustc_span::source_map::Span;
@@ -635,20 +636,64 @@ declare_clippy_lint! {
635636
"checking for emptiness of a `Vec` in the loop condition and popping an element in the body"
636637
}
637638

638-
pub struct Loops {
639+
declare_clippy_lint! {
640+
/// ### What it does
641+
/// Checks for infinite loops in a function where the return type is not `!`
642+
/// and lint accordingly.
643+
///
644+
/// ### Why is this bad?
645+
/// A loop should be gently exited somewhere, or at lease mark its parent function as
646+
/// never return (`!`).
647+
///
648+
/// ### Example
649+
/// ```no_run,ignore
650+
/// fn run_forever() {
651+
/// loop {
652+
/// // do something
653+
/// }
654+
/// }
655+
/// ```
656+
/// If infinite loops are as intended:
657+
/// ```no_run,ignore
658+
/// fn run_forever() -> ! {
659+
/// loop {
660+
/// // do something
661+
/// }
662+
/// }
663+
/// ```
664+
/// Otherwise add a `break` or `return` condition:
665+
/// ```no_run,ignore
666+
/// fn run_forever() {
667+
/// loop {
668+
/// // do something
669+
/// if condition {
670+
/// break;
671+
/// }
672+
/// }
673+
/// }
674+
/// ```
675+
#[clippy::version = "1.75.0"]
676+
pub INFINITE_LOOPS,
677+
restriction,
678+
"possibly unintended infinite loops"
679+
}
680+
681+
pub struct Loops<'tcx> {
639682
msrv: Msrv,
640683
enforce_iter_loop_reborrow: bool,
684+
parent_fn_ret_ty: Option<hir::FnRetTy<'tcx>>,
641685
}
642-
impl Loops {
686+
impl<'tcx> Loops<'tcx> {
643687
pub fn new(msrv: Msrv, enforce_iter_loop_reborrow: bool) -> Self {
644688
Self {
645689
msrv,
646690
enforce_iter_loop_reborrow,
691+
parent_fn_ret_ty: None,
647692
}
648693
}
649694
}
650695

651-
impl_lint_pass!(Loops => [
696+
impl_lint_pass!(Loops<'_> => [
652697
MANUAL_MEMCPY,
653698
MANUAL_FLATTEN,
654699
NEEDLESS_RANGE_LOOP,
@@ -669,9 +714,10 @@ impl_lint_pass!(Loops => [
669714
MANUAL_FIND,
670715
MANUAL_WHILE_LET_SOME,
671716
UNUSED_ENUMERATE_INDEX,
717+
INFINITE_LOOPS,
672718
]);
673719

674-
impl<'tcx> LateLintPass<'tcx> for Loops {
720+
impl<'tcx> LateLintPass<'tcx> for Loops<'tcx> {
675721
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
676722
let for_loop = higher::ForLoop::hir(expr);
677723
if let Some(higher::ForLoop {
@@ -707,10 +753,13 @@ impl<'tcx> LateLintPass<'tcx> for Loops {
707753
// check for `loop { if let {} else break }` that could be `while let`
708754
// (also matches an explicit "match" instead of "if let")
709755
// (even if the "match" or "if let" is used for declaration)
710-
if let ExprKind::Loop(block, _, LoopSource::Loop, _) = expr.kind {
756+
if let ExprKind::Loop(block, label, LoopSource::Loop, _) = expr.kind {
711757
// also check for empty `loop {}` statements, skipping those in #[panic_handler]
712758
empty_loop::check(cx, expr, block);
713759
while_let_loop::check(cx, expr, block);
760+
if let Some(parent_fn_ret_ty) = self.parent_fn_ret_ty {
761+
infinite_loops::check(cx, expr, block, label, parent_fn_ret_ty);
762+
}
714763
}
715764

716765
while_let_on_iterator::check(cx, expr);
@@ -722,11 +771,25 @@ impl<'tcx> LateLintPass<'tcx> for Loops {
722771
}
723772
}
724773

774+
fn check_fn(
775+
&mut self,
776+
_: &LateContext<'tcx>,
777+
kind: hir::intravisit::FnKind<'tcx>,
778+
decl: &'tcx hir::FnDecl<'tcx>,
779+
_: &'tcx hir::Body<'tcx>,
780+
_: Span,
781+
_: rustc_span::def_id::LocalDefId,
782+
) {
783+
if let hir::intravisit::FnKind::ItemFn(..) = kind {
784+
self.parent_fn_ret_ty = Some(decl.output);
785+
}
786+
}
787+
725788
extract_msrv_attr!(LateContext);
726789
}
727790

728-
impl Loops {
729-
fn check_for_loop<'tcx>(
791+
impl<'tcx> Loops<'tcx> {
792+
fn check_for_loop(
730793
&self,
731794
cx: &LateContext<'tcx>,
732795
pat: &'tcx Pat<'_>,

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