app_dirs crate no longer builds on nightly

[jdm]

   Compiling app_dirs v1.1.1
error[E0619]: the type of this value must be known in this context
  --> /Users/travis/.cargo/registry/src/github.heygears.com-1ecc6299db9ec823/app_dirs-1.1.1/src/imp/platform/macos.rs:10:40
   |
10 |         Ok(Component::RootDir.as_ref().into())
   |                                        ^^^^
error: aborting due to previous error

This is a regression from nightlies from a month ago.

[jdm]

This regressed between the 1/12 and 1/13 nightlies, so the range is 73ac5d6...51b0b37.

[jdm]

I suspect e0855ff out of that range, which is #46985. cc @Diggsey

[jdm]

The relevant code is https://github.com/AndyBarron/app-dirs-rs/blob/ab58239b56fd5bbad8e47ce97051b74f6a68a066/src/imp/platform/macos.rs#L8-L10.

[Diggsey]

According to the stability guidelines, it is acceptable to change type inference in ways that may occasionally require new type annotations. However, if this has a wider impact than just one crate, it may be worth reverting - I don't feel qualified to make that assessment. cc @BurntSushi

[Mark-Simulacrum]

Closing in favor of #48716.