chore(tests): Test trait override of MutableReference of struct (#3011)

Co-authored-by: Yordan Madzhunkov <[email protected]>

tooling/nargo_cli/tests/execution_success/trait_override_implementation/src/main.nr

@@ -40,6 +40,11 @@ impl F for Bar {
     fn f3(self) -> Field { 30 }
 }
 
+impl F for &mut Bar {
+    fn f1(self) -> Field { 101 }
+    fn f5(self) -> Field { 505 }
+}
+
 fn main(x: Field) {
     let first = Foo::method2(x);
     assert(first == 3 * x);
@@ -50,4 +55,17 @@ fn main(x: Field) {
     assert(bar.f3() == 30);
     assert(bar.f4() == 4);
     assert(bar.f5() == 50);
+
+    let mut bar_mut = Bar{};
+    assert((&mut bar_mut).f1() == 101);
+    assert((&mut bar_mut).f2() == 2);
+    assert((&mut bar_mut).f3() == 3);
+    assert((&mut bar_mut).f4() == 4);
+    assert((&mut bar_mut).f5() == 505);
+
+    assert(bar_mut.f1() == 10);
+    assert(bar_mut.f2() == 2);
+    assert(bar_mut.f3() == 30);
+    assert(bar_mut.f4() == 4);
+    assert(bar_mut.f5() == 50);
 }