Add regression test for issue 13077

Author: tesuji

tests/ui/needless_option_as_deref.fixed

@@ -52,3 +52,17 @@ struct S<'a> {
 fn from_field<'a>(s: &'a mut S<'a>) -> Option<&'a mut usize> {
     s.opt.as_deref_mut()
 }
+
+mod issue_non_copy_13077 {
+    pub fn something(mut maybe_side_effect: Option<&mut String>) {
+        for _ in 0..10 {
+            let _ = S { field: other(maybe_side_effect) };
+        }
+    }
+
+    fn other(_maybe_side_effect: Option<&mut String>) {
+        unimplemented!()
+    }
+
+    pub struct S { pub field: () }
+}

tests/ui/needless_option_as_deref.rs

@@ -52,3 +52,17 @@ struct S<'a> {
 fn from_field<'a>(s: &'a mut S<'a>) -> Option<&'a mut usize> {
     s.opt.as_deref_mut()
 }
+
+mod issue_non_copy_13077 {
+    pub fn something(mut maybe_side_effect: Option<&mut String>) {
+        for _ in 0..10 {
+            let _ = S { field: other(maybe_side_effect.as_deref_mut()) };
+        }
+    }
+
+    fn other(_maybe_side_effect: Option<&mut String>) {
+        unimplemented!()
+    }
+
+    pub struct S { pub field: () }
+}

tests/ui/needless_option_as_deref.stderr

@@ -19,5 +19,11 @@ error: derefed type is same as origin
 LL |     let _ = x.as_deref_mut();
    |             ^^^^^^^^^^^^^^^^ help: try: `x`
 
-error: aborting due to 3 previous errors
+error: derefed type is same as origin
+  --> tests/ui/needless_option_as_deref.rs:59:38
+   |
+LL |             let _ = S { field: other(maybe_side_effect.as_deref_mut()) };
+   |                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `maybe_side_effect`
+
+error: aborting due to 4 previous errors