Why does loop's `break` return expression end in a semi-colon?

[amb85]

In the Rust Book, returning values from loops example, we place a semi-colon ; after break counter * 2.

According to function bodies contain statements and expressions:

If you add a semicolon to the end of an expression, you turn it into a statement, which will then not return a value.

Why is break counter * 2; different and able to return a value from a loop such that the loop is an expression?

[alice]

The break expression assign a value to the loop, not to the break expression itself. Without a semicolon it might look like this:

let a = if counter == 10 {
    break counter * 2
} else {
    10
};

playground

In this case, the break expression has the never type ! since it never returns a value (the program jumps elsewhere), so the if compiles as the never type is convertible into another other type, including integers.