non-line mod without path attribute false positive

[matklad]

This code

fn main() {
    #[path="foo"]
    mod foo {
        mod bar;
    }
}

Fails to compile because there is no path on the bar, however I think it should work because there is a path on the foo. That is, the following is valid and will look for foo/bar.rs:

fn main() {}

#[path="foo"]
mod foo {
    mod bar;
}

cc @jseyfried d21e908