error[E0502]: cannot borrow `block_array` as mutable because it is also borrowed as immutable
  --> tests/ui/array/local_only/immutable_borrow.rs:8:28
   |
7  |     let block_slice = block_array.as_slice();
   |                       ----------- immutable borrow occurs here
8  |     let _mut_block_slice = block_array.as_mut_slice();
   |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^ mutable borrow occurs here
9  |     let _task = async {
10 |         println!("vec {:?}",block_slice);
   |                             ----------- immutable borrow later captured here by closure