1 files changed, 17 insertions, 0 deletions
diff --git a/src/test/ui/unboxed-closures/unboxed-closure-immutable-capture.rs b/src/test/ui/unboxed-closures/unboxed-closure-immutable-capture.rs
new file mode 100644
index 000000000..3eba9c4d4
--- /dev/null
+++ b/src/test/ui/unboxed-closures/unboxed-closure-immutable-capture.rs
@@ -0,0 +1,17 @@
+// Test that even unboxed closures that are capable of mutating their
+// environment cannot mutate captured variables that have not been
+// declared mutable (#18335)
+
+fn set(x: &mut usize) { *x = 0; }
+
+fn main() {
+    let x = 0;
+    move || x = 1; //~ ERROR cannot assign
+    move || set(&mut x); //~ ERROR cannot borrow
+    move || x = 1; //~ ERROR cannot assign
+    move || set(&mut x); //~ ERROR cannot borrow
+    || x = 1; //~ ERROR cannot assign
+    || set(&mut x); //~ ERROR cannot borrow
+    || x = 1; //~ ERROR cannot assign
+    || set(&mut x); //~ ERROR cannot borrow
+}