Warning: type alias is never used: Foo but it's used in newtype patern.

[Stargateur]

This simple code:

type Foo = i32;
struct Bar(Foo);

fn main() {
    let bar = Bar(42);

    println!("{:?}", bar.0);
}

produce the following warning:

   Compiling rustc 1.18.0
warning: type alias is never used: `Foo`
 --> src/main.rs:1:1
  |
1 | type Foo = i32;
  | ^^^^^^^^^^^^^^^
  |
  = note: #[warn(dead_code)] on by default

This issue is probably related to #43123

[Mark-Simulacrum]

Closing in favor of #18290.