For some reason this Go code works:

r := regexp.MustCompile("foo{bar}")

this seems strange since the "foo{bar}" doesn’t seem like a valid regular expression ({ and }) are not escaped.

On the contrary the equivalent Rust code (using regex crate) fails with an error:

let r = regex::Regex::new("foo{bar}").unwrap();

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
regex parse error:
    foo{bar}
        ^
error: repetition quantifier expects a valid decimal
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Is this a feature of Go’s regexp package to treat curly braces without valid repetition quantifiers literally, or am I missing something else?