DefaultMetadataLoader was changed to private, making it difficult to print out metadata

[Ramla-I]

Hi,

A recent commit bdacdfe made the DefaultMetadataLoader struct private to the crate.
This makes it impossible to print out the crate metadata using the given functions unless I define my own struct which implements the MetadataLoader trait. I'm currently just trying to understand the metadata file better, and am working with an older version of the Rust compiler so that I can access this type. I'm wondering why this type was made private.

Here is the code I'm using which works with an older version of the compiler:

fn main() {
    let path = std::env::args().nth(1).expect("no path given");
    let path = Path::new(&path);
    let triple = TargetTriple::from_triple("x86_64-apple-darwin");
    let target = Target::expect_builtin(&triple);
    let mut stdout = io::stdout();

    rustc_span::create_session_globals_then(Edition::Edition2018, || {
        let _ = locator::list_file_metadata(&target, path, &DefaultMetadataLoader, &mut stdout);
    });
}

[workingjubilee]

Because having types be publicly accessible when they do not need to be is not ideal, as none of these constitute a stable API. But as this issue demonstrates, sometimes people try to depend on them anyways.

"It's not stable API" remarks aside, please feel free to submit a PR making an API public again with a note about why. This will allow us to check on the noted reason and determine if it is still relevant if we decide to make it private once more. It likely won't stop us from breaking it, in the end, but it might at least give you a heads up and probably make it so that the next time we break it isn't "literally next week".