1 files changed, 78 insertions, 0 deletions
diff --git a/tests/ui/overloaded/overloaded-deref-count.rs b/tests/ui/overloaded/overloaded-deref-count.rs
new file mode 100644
index 00000000000..e2f1e10b5c8
--- /dev/null
+++ b/tests/ui/overloaded/overloaded-deref-count.rs
@@ -0,0 +1,78 @@
+// run-pass
+
+use std::cell::Cell;
+use std::ops::{Deref, DerefMut};
+use std::vec::Vec;
+
+struct DerefCounter<T> {
+    count_imm: Cell<usize>,
+    count_mut: usize,
+    value: T
+}
+
+impl<T> DerefCounter<T> {
+    fn new(value: T) -> DerefCounter<T> {
+        DerefCounter {
+            count_imm: Cell::new(0),
+            count_mut: 0,
+            value: value
+        }
+    }
+
+    fn counts(&self) -> (usize, usize) {
+        (self.count_imm.get(), self.count_mut)
+    }
+}
+
+impl<T> Deref for DerefCounter<T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        self.count_imm.set(self.count_imm.get() + 1);
+        &self.value
+    }
+}
+
+impl<T> DerefMut for DerefCounter<T> {
+    fn deref_mut(&mut self) -> &mut T {
+        self.count_mut += 1;
+        &mut self.value
+    }
+}
+
+pub fn main() {
+    let mut n = DerefCounter::new(0);
+    let mut v = DerefCounter::new(Vec::new());
+
+    let _ = *n; // Immutable deref + copy a POD.
+    assert_eq!(n.counts(), (1, 0));
+
+    let _ = (&*n, &*v); // Immutable deref + borrow.
+    assert_eq!(n.counts(), (2, 0)); assert_eq!(v.counts(), (1, 0));
+
+    let _ = (&mut *n, &mut *v); // Mutable deref + mutable borrow.
+    assert_eq!(n.counts(), (2, 1)); assert_eq!(v.counts(), (1, 1));
+
+    let mut v2 = Vec::new();
+    v2.push(1);
+
+    *n = 5; *v = v2; // Mutable deref + assignment.
+    assert_eq!(n.counts(), (2, 2)); assert_eq!(v.counts(), (1, 2));
+
+    *n -= 3; // Mutable deref + assignment with binary operation.
+    assert_eq!(n.counts(), (2, 3));
+
+    // Immutable deref used for calling a method taking &self. (The
+    // typechecker is smarter now about doing this.)
+    (*n).to_string();
+    assert_eq!(n.counts(), (3, 3));
+
+    // Mutable deref used for calling a method taking &mut self.
+    (*v).push(2);
+    assert_eq!(v.counts(), (1, 3));
+
+    // Check the final states.
+    assert_eq!(*n, 2);
+    let expected: &[_] = &[1, 2];
+    assert_eq!((*v), expected);
+}