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

1 files changed, 1 insertions, 1 deletions

diff --git a/src/test/compile-fail/macro-non-lifetime.rs b/src/test/compile-fail/macro-non-lifetime.rs
index a2706e83229..647d7aaa759 100644
--- a/src/test/compile-fail/macro-non-lifetime.rs
+++ b/src/test/compile-fail/macro-non-lifetime.rs
@@ -16,5 +16,5 @@ macro_rules! m { ($x:lifetime) => { } }
 
 fn main() {
     m!(a);
-    //~^ ERROR expected a lifetime, found `a`
+    //~^ ERROR no rules expected the token `a`
 }