error[E0434]: can't capture dynamic environment in a fn item
  --> $DIR/capture1.rs:5:32
   |
LL |     fn foo() -> isize { return bar; }
   |                                ^^^
   |
   = help: use the `|| { ... }` closure form instead

error: aborting due to previous error

For more information about this error, try `rustc --explain E0434`.