message: Make all code paths in main return an explcit exit code
diff: @@ -73,7 +73,7 @@ impl From<&str> for Input {
  const MAX_PRETTY_WIDTH: usize = 80;
  -fn main() {
  +fn main() -> ! {
  let mut writer = BufferedStandardStream::stderr(ColorChoice::Auto);
  let term_config = codespan_reporting::term::Config::default();
  @@ -105,6 +105,8 @@ fn main() {
  let doc = context.ann(&term, &r#type).into_doc();
  println!("{}", doc.pretty(pretty_width));
  +
  + std::process::exit(0);
  } else {
  std::process::exit(1);
  }
  @@ -129,6 +131,8 @@ fn main() {
  let doc = context.ann(&term, &r#type).into_doc();
  println!("{}", doc.pretty(pretty_width));
  +
  + std::process::exit(0);
  } else {
  std::process::exit(1);
  }
  @@ -151,6 +155,8 @@ fn main() {
  let doc = context.term(&r#type).into_doc();
  println!("{}", doc.pretty(pretty_width));
  +
  + std::process::exit(0);
  } else {
  std::process::exit(1);
  }
  