1 files changed, 15 insertions, 0 deletions
diff --git a/tests/ui/mut/mut-pattern-internal-mutability.rs b/tests/ui/mut/mut-pattern-internal-mutability.rs
new file mode 100644
index 000000000..bcee878e3
--- /dev/null
+++ b/tests/ui/mut/mut-pattern-internal-mutability.rs
@@ -0,0 +1,15 @@
+fn main() {
+    let foo = &mut 1;
+
+    let &mut x = foo;
+    x += 1; //~ ERROR cannot assign twice to immutable variable `x`
+
+    // explicitly mut-ify internals
+    let &mut mut x = foo;
+    x += 1;
+
+    // check borrowing is detected successfully
+    let &mut ref x = foo;
+    *foo += 1; //~ ERROR cannot assign to `*foo` because it is borrowed
+    drop(x);
+}