error[E0503]: cannot use `x` because it was mutably borrowed --> $DIR/unboxed-closures-borrow-conflict.rs:9:14 | LL | let f = || x += 1; | -- - borrow occurs due to use of `x` in closure | | | borrow of `x` occurs here LL | let _y = x; | ^ use of borrowed `x` LL | f; | - borrow later used here error: aborting due to previous error For more information about this error, try `rustc --explain E0503`.