having to add the return here concerns me. is it correct?

I would think that just bail() (without both return and semicolon) should work?

me too! but looks like it doesn't. I blame macro shenanigans?

error[E0308]: if and else have incompatible types
   --> src/cargo/util/toml/targets.rs:159:13
    |
159 | /             if legacy_path.exists() {
160 | |                 warnings.push(format!(
161 | |                     "path `{}` was erroneously implicitly accepted for library `{}`,\n\
162 | |                      please rename the file to `src/lib.rs` or set lib.path in Cargo.toml",
...   |
168 | |                 bail()
169 | |             }
    | |_____________^ expected struct `std::path::PathBuf`, found enum `std::result::Result`
    |
    = note: expected type `std::path::PathBuf`
               found type `std::result::Result<std::option::Option<core::manifest::Target>, failure::Error>`

Hm, weird.... Anyway, I hope we can get rid of this closure altogether, as I've mentioned in other comments.

Let's use the bail macro here as well?

sadly looks like no, because bail returns failure::Error and there's a codepath that buffers error strings in a vec

Hm, let's just wrap this if-let into an addition if edition >= 2018, so as to avoid introducing local closures?

of course.. I find out you can't use && with if let and somehow forgot about just nesting 😆

also I assumed the closure was free. good to know it's not.

Hm, let's add && edition == 2015 to this condition, instead of introducing the bail closure?