1 files changed, 16 insertions, 0 deletions
diff --git a/tests/ui/pattern/issue-52240.rs b/tests/ui/pattern/issue-52240.rs
new file mode 100644
index 00000000000..5def557789f
--- /dev/null
+++ b/tests/ui/pattern/issue-52240.rs
@@ -0,0 +1,16 @@
+// issue-52240: Can turn immutable into mut with `ref mut`
+
+enum Foo {
+    Bar(i32),
+}
+
+fn main() {
+    let arr = vec!(Foo::Bar(0));
+    if let (Some(Foo::Bar(ref mut val)), _) = (&arr.get(0), 0) {
+        //~^ ERROR cannot borrow data in a `&` reference as mutable
+        *val = 9001;
+    }
+    match arr[0] {
+        Foo::Bar(ref s) => println!("{}", s)
+    }
+}