error[E0506]: cannot assign to `_a` because it is borrowed --> $DIR/borrowck-imm-ref-to-mut-rec-field-issue-3162-c.rs:6:9 | LL | let b = &mut _a; | ------- `_a` is borrowed here ... LL | _a = 4; | ^^^^^^ `_a` is assigned to here but it was already borrowed ... LL | drop(b); | - borrow later used here error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0506`.