Explain unusual debugging code in librustc

Introduced in #47828 to help track down some bugs, it landed a bit hastily so
this is intended on cleaning it up a bit.

src/librustc_resolve/resolve_imports.rs

@@ -1026,9 +1026,14 @@ fn import_path_to_string(names: &[SpannedIdent],
  if names.is_empty() {
  import_directive_subclass_to_string(subclass)
  } else {
- let x = format!("{}::{}",
- names_to_string(names),
- import_directive_subclass_to_string(subclass));
+ // Note that this code looks a little wonky, it's currently here to
+ // hopefully help debug #48116, but otherwise isn't intended to
+ // cause any problems.
+ let x = format!(
+ "{}::{}",
+ names_to_string(names),
+ import_directive_subclass_to_string(subclass),
+ );
  assert!(!names.is_empty());
  assert!(!x.starts_with("::"));
  return x