From 99ce411ed67fd73fc9d3e4afebbdf3472d25bd10 Mon Sep 17 00:00:00 2001
From: Samuel Tardieu <sam@rfc1149.net>
Date: Sun, 6 Oct 2024 17:38:36 +0200
Subject: [PATCH] `infinite_loop`: continuing an outer loop leaves the inner
 loop

---
 clippy_lints/src/loops/infinite_loop.rs | 17 ++++++-
 tests/ui/infinite_loops.rs              | 38 +++++++++++++++
 tests/ui/infinite_loops.stderr          | 64 ++++++++++++++++++++++++-
 3 files changed, 117 insertions(+), 2 deletions(-)

diff --git a/clippy_lints/src/loops/infinite_loop.rs b/clippy_lints/src/loops/infinite_loop.rs
index 64ae08070152..e25c03db5344 100644
--- a/clippy_lints/src/loops/infinite_loop.rs
+++ b/clippy_lints/src/loops/infinite_loop.rs
@@ -42,6 +42,7 @@ pub(super) fn check<'tcx>(
     let mut loop_visitor = LoopVisitor {
         cx,
         label,
+        inner_labels: label.into_iter().collect(),
         is_finite: false,
         loop_depth: 0,
     };
@@ -93,6 +94,7 @@ fn get_parent_fn_ret_ty<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) -> Option
 struct LoopVisitor<'hir, 'tcx> {
     cx: &'hir LateContext<'tcx>,
     label: Option<Label>,
+    inner_labels: Vec<Label>,
     loop_depth: usize,
     is_finite: bool,
 }
@@ -108,11 +110,24 @@ impl<'hir> Visitor<'hir> for LoopVisitor<'hir, '_> {
                     self.is_finite = true;
                 }
             },
+            ExprKind::Continue(hir::Destination { label, .. }) => {
+                // Check whether we are leaving this loop by continuing into an outer loop
+                // whose label we did not encounter.
+                if label.is_some_and(|label| !self.inner_labels.contains(&label)) {
+                    self.is_finite = true;
+                }
+            },
             ExprKind::Ret(..) => self.is_finite = true,
-            ExprKind::Loop(..) => {
+            ExprKind::Loop(_, label, _, _) => {
+                if let Some(label) = label {
+                    self.inner_labels.push(*label);
+                }
                 self.loop_depth += 1;
                 walk_expr(self, ex);
                 self.loop_depth -= 1;
+                if label.is_some() {
+                    self.inner_labels.pop();
+                }
             },
             _ => {
                 // Calls to a function that never return
diff --git a/tests/ui/infinite_loops.rs b/tests/ui/infinite_loops.rs
index b2d522fa011b..b6cb7ff49b0a 100644
--- a/tests/ui/infinite_loops.rs
+++ b/tests/ui/infinite_loops.rs
@@ -390,4 +390,42 @@ fn span_inside_fn() {
     }
 }
 
+fn continue_outer() {
+    // Should not lint (issue #13511)
+    let mut count = 0;
+    'outer: loop {
+        if count != 0 {
+            break;
+        }
+
+        loop {
+            count += 1;
+            continue 'outer;
+        }
+    }
+
+    // This should lint as we continue the loop itself
+    'infinite: loop {
+        //~^ ERROR: infinite loop detected
+        loop {
+            continue 'infinite;
+        }
+    }
+    // This should lint as we continue an inner loop
+    loop {
+        //~^ ERROR: infinite loop detected
+        'inner: loop {
+            loop {
+                continue 'inner;
+            }
+        }
+    }
+
+    // This should lint as we continue the loop itself
+    loop {
+        //~^ ERROR: infinite loop detected
+        continue;
+    }
+}
+
 fn main() {}
diff --git a/tests/ui/infinite_loops.stderr b/tests/ui/infinite_loops.stderr
index ec6bd81dc175..7635a7442f4a 100644
--- a/tests/ui/infinite_loops.stderr
+++ b/tests/ui/infinite_loops.stderr
@@ -255,5 +255,67 @@ LL | |     })
    |
    = help: if this is not intended, try adding a `break` or `return` condition in the loop
 
-error: aborting due to 17 previous errors
+error: infinite loop detected
+  --> tests/ui/infinite_loops.rs:408:5
+   |
+LL | /     'infinite: loop {
+LL | |
+LL | |         loop {
+LL | |             continue 'infinite;
+LL | |         }
+LL | |     }
+   | |_____^
+   |
+help: if this is intentional, consider specifying `!` as function return
+   |
+LL | fn continue_outer() -> ! {
+   |                     ++++
+
+error: infinite loop detected
+  --> tests/ui/infinite_loops.rs:415:5
+   |
+LL | /     loop {
+LL | |
+LL | |         'inner: loop {
+LL | |             loop {
+...  |
+LL | |         }
+LL | |     }
+   | |_____^
+   |
+help: if this is intentional, consider specifying `!` as function return
+   |
+LL | fn continue_outer() -> ! {
+   |                     ++++
+
+error: infinite loop detected
+  --> tests/ui/infinite_loops.rs:417:9
+   |
+LL | /         'inner: loop {
+LL | |             loop {
+LL | |                 continue 'inner;
+LL | |             }
+LL | |         }
+   | |_________^
+   |
+help: if this is intentional, consider specifying `!` as function return
+   |
+LL | fn continue_outer() -> ! {
+   |                     ++++
+
+error: infinite loop detected
+  --> tests/ui/infinite_loops.rs:425:5
+   |
+LL | /     loop {
+LL | |
+LL | |         continue;
+LL | |     }
+   | |_____^
+   |
+help: if this is intentional, consider specifying `!` as function return
+   |
+LL | fn continue_outer() -> ! {
+   |                     ++++
+
+error: aborting due to 21 previous errors