1 files changed, 20 insertions, 0 deletions
diff --git a/tests/ui/borrowck/issue-115259-suggest-iter-mut.rs b/tests/ui/borrowck/issue-115259-suggest-iter-mut.rs
new file mode 100644
index 000000000..e0f6ab132
--- /dev/null
+++ b/tests/ui/borrowck/issue-115259-suggest-iter-mut.rs
@@ -0,0 +1,20 @@
+// run-rustfix
+#![allow(unused_mut)]
+#![allow(dead_code)]
+
+pub trait Layer {
+    fn process(&mut self) -> u32;
+}
+
+pub struct State {
+    layers: Vec<Box<dyn Layer>>,
+}
+
+impl State {
+    pub fn process(&mut self) -> u32 {
+        self.layers.iter().fold(0, |result, mut layer| result + layer.process())
+        //~^ ERROR cannot borrow `**layer` as mutable, as it is behind a `&` reference
+    }
+}
+
+fn main() {}