pub unit struct constructors can't be resolved cross-crate

[bblum]

...even though mentioning the type works fine. This doesn't work:

use std::util;

fn main() {
    let _: Option<util::NonCopyable> = Some(util::NonCopyable);
}

but replacing the expression with None works fine.

nominating well-covered

[emberian]

Dupe of #7634