error[E0277]: cannot add `std::vec::Vec<B>` to `()`
  --> $DIR/issue-2149.rs:18:33
   |
LL |         for elt in self { r = r + f(*elt); }
   |                                 ^ no implementation for `() + std::vec::Vec<B>`
   |
   = help: the trait `std::ops::Add<std::vec::Vec<B>>` is not implemented for `()`

error[E0599]: no method named `bind` found for type `[&str; 1]` in the current scope
  --> $DIR/issue-2149.rs:23:12
   |
LL |     ["hi"].bind(|x| [x] );
   |            ^^^^
   |
   = help: items from traits can only be used if the trait is implemented and in scope
   = note: the following trait defines an item `bind`, perhaps you need to implement it:
           candidate #1: `vec_monad`

error: aborting due to 2 previous errors

Some errors occurred: E0277, E0599.
For more information about an error, try `rustc --explain E0277`.