Auto merge of #51480 - dtolnay:lifetime, r=kennytm

Enable fall through past $:lifetime matcher

```rust
macro_rules! is_lifetime {
    ($lifetime:lifetime) => { true };
    ($other:tt) => { false };
}

fn main() {
    println!("{}", is_lifetime!('lifetime));
    println!("{}", is_lifetime!(@));
}
```

Before this fix, the `is_lifetime!` invocation would fail to compile with:

```
error: expected a lifetime, found `@`
 --> src/main.rs:8:33
  |
8 |     println!("{}", is_lifetime!(@));
  |                                 ^
```

Fixes #50903.
Fixes #51477.

r? @kennytm

0 files changed, 0 insertions, 0 deletions