Function is_rust_path 

fn is_rust_path(dest: &str) -> bool

Whether dest is a Rust path as an inline link destination writes it: identifiers joined by ::, with an optional () or ! suffix. A URL with a /, ., #, ? or lone : never is one, even with a :: in it (https://a.b/c::d). A bare Foo can be either, so the caller also asks for a ::.