1 files changed, 51 insertions, 0 deletions
diff --git a/tests/ui/collections/hashset-connected-border-12860.rs b/tests/ui/collections/hashset-connected-border-12860.rs
new file mode 100644
index 00000000000..40185bef7c8
--- /dev/null
+++ b/tests/ui/collections/hashset-connected-border-12860.rs
@@ -0,0 +1,51 @@
+//! Regression test for https://github.com/rust-lang/rust/issues/12860
+
+//@ run-pass
+use std::collections::HashSet;
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash)]
+struct XYZ {
+    x: isize,
+    y: isize,
+    z: isize
+}
+
+fn main() {
+    let mut connected = HashSet::new();
+    let mut border = HashSet::new();
+
+    let middle = XYZ{x: 0, y: 0, z: 0};
+    border.insert(middle);
+
+    while !border.is_empty() && connected.len() < 10000 {
+        let choice = *(border.iter().next().unwrap());
+        border.remove(&choice);
+        connected.insert(choice);
+
+        let cxp = XYZ{x: choice.x + 1, y: choice.y, z: choice.z};
+        let cxm = XYZ{x: choice.x - 1, y: choice.y, z: choice.z};
+        let cyp = XYZ{x: choice.x, y: choice.y + 1, z: choice.z};
+        let cym = XYZ{x: choice.x, y: choice.y - 1, z: choice.z};
+        let czp = XYZ{x: choice.x, y: choice.y, z: choice.z + 1};
+        let czm = XYZ{x: choice.x, y: choice.y, z: choice.z - 1};
+
+        if !connected.contains(&cxp) {
+            border.insert(cxp);
+        }
+        if  !connected.contains(&cxm){
+            border.insert(cxm);
+        }
+        if !connected.contains(&cyp){
+            border.insert(cyp);
+        }
+        if !connected.contains(&cym) {
+            border.insert(cym);
+        }
+        if !connected.contains(&czp){
+            border.insert(czp);
+        }
+        if !connected.contains(&czm) {
+            border.insert(czm);
+        }
+    }
+}