src/compatibility/raw_identifiers.md

# Raw identifiers

Rust, like many programming languages, has the concept of "keywords".
These identifiers mean something to the language, and so you cannot use them in
places like variable names, function names, and other places.
Raw identifiers let you use keywords where they would not normally be allowed.
This is particularly useful when Rust introduces new keywords, and a library
using an older edition of Rust has a variable or function with the same name
as a keyword introduced in a newer edition.

For example, consider a crate `foo` compiled with the 2015 edition of Rust that
exports a function named `try`. This keyword is reserved for a new feature in
the 2018 edition, so without raw identifiers, we would have no way to name the
function.

```rust,ignore
extern crate foo;

fn main() {
    foo::try();
}
```

You'll get this error:

```text
error: expected identifier, found keyword `try`
 --> src/main.rs:4:4
  |
4 | foo::try();
  |      ^^^ expected identifier, found keyword
```

You can write this with a raw identifier:

```rust,ignore
extern crate foo;

fn main() {
    foo::r#try();
}
```