Rust namespaces everything in the standard library to std:: or core::, and has a clear distinction between them.
However, it does implicitly include the entirety of the std::prelude namespace (https://doc.rust-lang.org/std/prelude/index.html) into every source file, as well as including every macro directly exported under std:: (including println!). This enables the unprefixed use of things like Result, Option, Some, Send, etc.
The prelude and std:: macros are the closest thing that Rust has to a global namespace, and even they can be disabled in crates that specifically request it.
However, it does implicitly include the entirety of the std::prelude namespace (https://doc.rust-lang.org/std/prelude/index.html) into every source file, as well as including every macro directly exported under std:: (including println!). This enables the unprefixed use of things like Result, Option, Some, Send, etc.
The prelude and std:: macros are the closest thing that Rust has to a global namespace, and even they can be disabled in crates that specifically request it.