1 files changed, 35 insertions, 0 deletions
diff --git a/src/test/ui/dynamically-sized-types/dst-deref-mut.rs b/src/test/ui/dynamically-sized-types/dst-deref-mut.rs
new file mode 100644
index 000000000..1d62f42bd
--- /dev/null
+++ b/src/test/ui/dynamically-sized-types/dst-deref-mut.rs
@@ -0,0 +1,35 @@
+// run-pass
+// Test that a custom deref with a fat pointer return type does not ICE
+
+
+use std::ops::{Deref, DerefMut};
+
+pub struct Arr {
+    ptr: Box<[usize]>
+}
+
+impl Deref for Arr {
+    type Target = [usize];
+
+    fn deref(&self) -> &[usize] {
+        panic!();
+    }
+}
+
+impl DerefMut for Arr {
+    fn deref_mut(&mut self) -> &mut [usize] {
+        &mut *self.ptr
+    }
+}
+
+pub fn foo(arr: &mut Arr) {
+    let x: &mut [usize] = &mut **arr;
+    assert_eq!(x[0], 1);
+    assert_eq!(x[1], 2);
+    assert_eq!(x[2], 3);
+}
+
+fn main() {
+    let mut a = Arr { ptr: Box::new([1, 2, 3]) };
+    foo(&mut a);
+}