1 files changed, 15 insertions, 0 deletions
diff --git a/src/test/ui/typeck/assign-non-lval-derefmut.rs b/src/test/ui/typeck/assign-non-lval-derefmut.rs
new file mode 100644
index 000000000..ec1882f52
--- /dev/null
+++ b/src/test/ui/typeck/assign-non-lval-derefmut.rs
@@ -0,0 +1,15 @@
+// run-rustfix
+
+fn main() {
+    let x = std::sync::Mutex::new(1usize);
+    x.lock().unwrap() = 2;
+    //~^ ERROR invalid left-hand side of assignment
+    x.lock().unwrap() += 1;
+    //~^ ERROR binary assignment operation `+=` cannot be applied to type `MutexGuard<'_, usize>`
+
+    let mut y = x.lock().unwrap();
+    y = 2;
+    //~^ ERROR mismatched types
+    y += 1;
+    //~^ ERROR binary assignment operation `+=` cannot be applied to type `MutexGuard<'_, usize>`
+}