trait_and_borrow.rs

#![feature(impl_trait_in_bindings)]

fn iter_returner<'a>(names: Vec<&'a str>) -> impl Iterator<Item=String> + 'a  {
    let it = names.into_iter()
        .map(|n| format!("hello {}", n))
        .map(String::from);
    it
}

fn main() {
    let i: impl Iterator<Item=String> = iter_returner(vec!["name1", "name2", "name3"]);
    println!("{}", i.collect());
}

// warning: the feature `impl_trait_in_bindings` is incomplete and may cause the compiler to crash
//  --> test.rs:1:12
//   |
// 1 | #![feature(impl_trait_in_bindings)]
//   |            ^^^^^^^^^^^^^^^^^^^^^^
//   |
//   = note: `#[warn(incomplete_features)]` on by default

// error[E0283]: type annotations needed: cannot resolve `_: std::iter::FromIterator<std::string::String>`
//   --> test.rs:12:22
//    |
// 12 |     println!("{}", i.collect());
//    |                      ^^^^^^^

// error: aborting due to previous error

// For more information about this error, try `rustc --explain E0283`.