message: Make exported_symbols return &str
  Summary: A more natural type given what it does.
diff: @@ -22,7 +22,7 @@ use crate::{
  use indexmap::IndexMap;
  // Which symbols are exported by a module
  -pub fn exported_symbols(module: &AstModule) -> Vec<(SpanLoc, String)> {
  +pub fn exported_symbols(module: &AstModule) -> Vec<(SpanLoc, &str)> {
  // Map since we only want to store the first of each export
  // IndexMap since we want the order to match the order they were defined in
  let mut result = IndexMap::new();
  @@ -40,7 +40,7 @@ pub fn exported_symbols(module: &AstModule) -> Vec<(SpanLoc, String)> {
  result
  .into_iter()
  .filter(|(name, _)| !name.starts_with('_'))
  - .map(|(name, span)| (module.codemap.look_up_span(span), name.to_owned()))
  + .map(|(name, span)| (module.codemap.look_up_span(span), name.as_str()))
  .collect()
  }
  @@ -56,7 +56,7 @@ mod test {
  #[test]
  fn test_lint_exported() {
  - let res = exported_symbols(&module(
  + let modu = module(
  r#"
  load("test", "a")
  def b(): pass
  @@ -64,7 +64,8 @@ d = 1
  def _e(): pass
  d = 2
  "#,
  - ));
  + );
  + let res = exported_symbols(&modu);
  assert_eq!(
  res.map(|(loc, name)| format!("{} {}", loc, name)),
  &["X:3:5: 3:6 b", "X:4:1: 4:2 d"]
  