Avoid UncanonicalizedIter during prefetch

It's not really necessary. It's okay if it takes us slightly longer to
generate an error.

src/cargo/sources/registry/index.rs

@@ -112,6 +112,9 @@ impl<'s> Iterator for UncanonicalizedIter<'s> {
  return None;
  }
 
+ // TODO:
+ // This implementation can currently generate paths like en/v-/env_logger,
+ // which doesn't _seem_ like a useful candidate to test?
  let ret = Some(
  self.input
  .chars()
@@ -494,15 +497,16 @@ impl<'cfg> RegistryIndex<'cfg> {
 
  // Seed the prefetching with the root dependencies.
  for dep in deps {
- let raw_path = relative(&*dep.package_name());
- for relative in UncanonicalizedIter::new(&raw_path).take(1024) {
- load.prefetch(
- root,
- &Path::new(&relative),
- dep.package_name(),
- dep.version_req(),
- )?;
- }
+ let relative = relative(&*dep.package_name());
+ // NOTE: We do not use UncanonicalizedIter here or below because if the user gave a
+ // misspelling, it's fine if we don't prefetch their misspelling. The resolver will be
+ // a bit slower, but then give them an error.
+ load.prefetch(
+ root,
+ &Path::new(&relative),
+ dep.package_name(),
+ dep.version_req(),
+ )?;
  }
 
  // Now, continuously iterate by walking dependencies we've loaded and fetching the index
@@ -567,17 +571,13 @@ impl<'cfg> RegistryIndex<'cfg> {
  continue;
  }
 
- let raw_path = relative(&*dep.package_name());
- for relative in UncanonicalizedIter::new(&raw_path).take(1024) {
- // NOTE: Many of these prefetches will "miss", but that's okay.
- // They're going to be pipelined anyway.
- load.prefetch(
- root,
- Path::new(&relative),
- dep.package_name(),
- dep.version_req(),
- )?;
- }
+ let relative = relative(&*dep.package_name());
+ load.prefetch(
+ root,
+ Path::new(&relative),
+ dep.package_name(),
+ dep.version_req(),
+ )?;
  }
  }
  }