[millstone]

What does functional language mean here?

Rust is not referentially transparent, does not model effects (any function can rm -Rf your drive), permits shared mutable state (RefCell, etc) includes statements not just expressions (break, return). Its most important safeguard is its affine type system, which is absent from Haskell.

[steveklabnik]

Break and return are both expressions in Rust.

Item declarations, let statements, expression statements, and macro invocation statements are the four kinds of statements in Rust.