error[E0425]: cannot find function `foo` in this scope
  --> $DIR/issue-4366.rs:18:29
   |
LL |         fn sub() -> isize { foo(); 1 }
   |                             ^^^ not found in this scope
   |
help: consider importing this function
   |
LL +         use foo::foo;
   |

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0425`.