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eliminate the second visit to save a bit performance.

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Thanks @y21 for the hint!
This commit is contained in:
J-ZhengLi 2023-11-27 10:30:47 +08:00
parent 3e9a6d142e
commit 0d26f9183b
1 changed files with 14 additions and 25 deletions
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39
clippy_lints/src/loops/infinite_loops.rs
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@ -34,27 +34,15 @@ pub(super) fn check<'tcx>(
return; return;
} }
// First, find any `break` or `return` without entering any inner loop, let mut loop_visitor = LoopVisitor {
// then, find `return` or labeled `break` which breaks this loop with entering inner loop,
// otherwise this loop is a infinite loop.
let mut direct_visitor = LoopVisitor {
cx, cx,
label, label,
is_finite: false, is_finite: false,
enter_nested_loop: false, loop_depth: 0,
}; };
direct_visitor.visit_block(loop_block); loop_visitor.visit_block(loop_block);
let is_finite_loop = direct_visitor.is_finite || { let is_finite_loop = loop_visitor.is_finite;
let mut inner_loop_visitor = LoopVisitor {
cx,
label,
is_finite: false,
enter_nested_loop: true,
};
inner_loop_visitor.visit_block(loop_block);
inner_loop_visitor.is_finite
};
if !is_finite_loop { if !is_finite_loop {
span_lint_and_then(cx, INFINITE_LOOPS, expr.span, "infinite loop detected", |diag| { span_lint_and_then(cx, INFINITE_LOOPS, expr.span, "infinite loop detected", |diag| {
@ -103,26 +91,27 @@ fn get_parent_fn_ret_ty<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) -> Option
struct LoopVisitor<'hir, 'tcx> { struct LoopVisitor<'hir, 'tcx> {
cx: &'hir LateContext<'tcx>, cx: &'hir LateContext<'tcx>,
label: Option<Label>, label: Option<Label>,
loop_depth: usize,
is_finite: bool, is_finite: bool,
enter_nested_loop: bool,
} }
impl<'hir> Visitor<'hir> for LoopVisitor<'hir, '_> { impl<'hir> Visitor<'hir> for LoopVisitor<'hir, '_> {
fn visit_expr(&mut self, ex: &'hir Expr<'_>) { fn visit_expr(&mut self, ex: &'hir Expr<'_>) {
match &ex.kind { match &ex.kind {
ExprKind::Break(hir::Destination { label, .. }, ..) => { ExprKind::Break(hir::Destination { label, .. }, ..) => {
// When entering nested loop, only by breaking this loop's label // Assuming breaks the loop when `loop_depth` is 0,
// would be considered as exiting this loop. // as it could only means this `break` breaks current loop or any of its upper loop.
if self.enter_nested_loop { // Or, the depth is not zero but the label is matched.
if label.is_some() && *label == self.label { if self.loop_depth == 0 || (label.is_some() && *label == self.label) {
self.is_finite = true;
}
} else {
self.is_finite = true; self.is_finite = true;
} }
}, },
ExprKind::Ret(..) => self.is_finite = true, ExprKind::Ret(..) => self.is_finite = true,
ExprKind::Loop(..) if !self.enter_nested_loop => (), ExprKind::Loop(..) => {
self.loop_depth += 1;
walk_expr(self, ex);
self.loop_depth = self.loop_depth.saturating_sub(1);
},
_ => { _ => {
// Calls to a function that never return // Calls to a function that never return
if let Some(did) = fn_def_id(self.cx, ex) { if let Some(did) = fn_def_id(self.cx, ex) {