error[E0382]: borrow of moved value: `a.b`
  --> $DIR/issue-52669.rs:13:5
   |
LL | fn bar(mut a: A) -> B {
   |        ----- move occurs because `a` has type `A`, which does not implement the `Copy` trait
LL |     a.b = B;
LL |     foo(a);
   |         - value moved here
LL |     a.b.clone()
   |     ^^^^^^^^^^^ value borrowed here after move

error: aborting due to previous error

For more information about this error, try `rustc --explain E0382`.