Type inference error

code.rs

        let def_ids: Arc<DefIdSet> = tcx.collect_and_partition_mono_items(LOCAL_CRATE).0;     
        let def_ids: DefIdSet = def_ids.borrow().clone();                            

error.txt

error[E0282]: type annotations needed
    --> src/librustc_interface/passes.rs:1108:50
     |
1108 |         let def_ids: DefIdSet = def_ids.borrow().clone();
     |                                                  ^^^^^ cannot infer type for `Borrowed`
     |
     = note: type must be known at this point

error: aborting due to previous error