1 files changed, 30 insertions, 0 deletions
diff --git a/src/test/ui/compile-fail-migration/mut-pattern-internal-mutability.rs b/src/test/ui/compile-fail-migration/mut-pattern-internal-mutability.rs
new file mode 100644
index 00000000000..a05ee64937e
--- /dev/null
+++ b/src/test/ui/compile-fail-migration/mut-pattern-internal-mutability.rs
@@ -0,0 +1,30 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// revisions: ast mir
+//[mir]compile-flags: -Z borrowck=mir
+
+fn main() {
+    let foo = &mut 1;
+
+    let &mut x = foo;
+    x += 1; //[ast]~ ERROR cannot assign twice to immutable variable
+            //[mir]~^ 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; //[ast]~ ERROR cannot assign to `*foo` because it is borrowed
+    //[mir]~^ ERROR cannot assign to `*foo` because it is borrowed
+    drop(x);
+}