Return expressions without a semicolon compile

[pmarcelll]

My "investigation": #17257 (comment)

Test case:

fn foo() -> i32 {
    return 1 // no semicolon
}

fn main() {
    println!("{}", foo());
}

This compiles, but the reference doesn't mention, that is should.

[Aatch]

The reference also doesn't say it shouldn't. This is expected behaviour as it allows this to be valid Rust code:

let x = match foo {
    1 => do_1(),
    2 => do_2(),
    _ => return 0
}

Since a semicolon here wouldn't be valid syntax. Note that the semicolon isn't part of the return expression at all, it is instead part of statement syntax.

Referencing your comment in the linked issue, there are many constructs that you're unlikely to see in regular Rust code that are, nonetheless, valid. Take a look at this test for some crazy stuff that is perfectly valid Rust code.

[pmarcelll]

Ok, thanks. It really makes sense now (and it makes things a bit more flexible and ergonomic), but I think it should be mentioned in TRPL.