Remove `vec_linked_list`.

It provides a way to effectively embed a linked list within an
`IndexVec` and also iterate over that list. It's written in a very
generic way, involving two traits `Links` and `LinkElem`. But the
`Links` trait is only impl'd for `IndexVec` and `&IndexVec`, and the
whole thing is only used in one module within `rustc_borrowck`. So I
think it's over-engineered and hard to read. Plus it has no comments.

This commit removes it, and adds a (non-generic) local iterator for the
use within `rustc_borrowck`. Much simpler.

2 files changed, 0 insertions, 71 deletions

diff --git a/compiler/rustc_data_structures/src/lib.rs b/compiler/rustc_data_structures/src/lib.rs
index 2e5f3806b12..407ee0453e5 100644
--- a/compiler/rustc_data_structures/src/lib.rs
+++ b/compiler/rustc_data_structures/src/lib.rs
@@ -85,7 +85,6 @@ pub mod temp_dir;
 pub mod transitive_relation;
 pub mod unhash;
 pub mod unord;
-pub mod vec_linked_list;
 pub mod work_queue;
 
 mod atomic_ref;
diff --git a/compiler/rustc_data_structures/src/vec_linked_list.rs b/compiler/rustc_data_structures/src/vec_linked_list.rs
deleted file mode 100644
index fda72c9a3b2..00000000000
--- a/compiler/rustc_data_structures/src/vec_linked_list.rs
+++ /dev/null
@@ -1,70 +0,0 @@
-use rustc_index::{Idx, IndexVec};
-
-pub fn iter<Ls>(
-    first: Option<Ls::LinkIndex>,
-    links: &Ls,
-) -> impl Iterator<Item = Ls::LinkIndex> + '_
-where
-    Ls: Links,
-{
-    VecLinkedListIterator { links, current: first }
-}
-
-pub struct VecLinkedListIterator<Ls>
-where
-    Ls: Links,
-{
-    links: Ls,
-    current: Option<Ls::LinkIndex>,
-}
-
-impl<Ls> Iterator for VecLinkedListIterator<Ls>
-where
-    Ls: Links,
-{
-    type Item = Ls::LinkIndex;
-
-    fn next(&mut self) -> Option<Ls::LinkIndex> {
-        if let Some(c) = self.current {
-            self.current = <Ls as Links>::next(&self.links, c);
-            Some(c)
-        } else {
-            None
-        }
-    }
-}
-
-pub trait Links {
-    type LinkIndex: Copy;
-
-    fn next(links: &Self, index: Self::LinkIndex) -> Option<Self::LinkIndex>;
-}
-
-impl<Ls> Links for &Ls
-where
-    Ls: Links,
-{
-    type LinkIndex = Ls::LinkIndex;
-
-    fn next(links: &Self, index: Ls::LinkIndex) -> Option<Ls::LinkIndex> {
-        <Ls as Links>::next(links, index)
-    }
-}
-
-pub trait LinkElem {
-    type LinkIndex: Copy;
-
-    fn next(elem: &Self) -> Option<Self::LinkIndex>;
-}
-
-impl<L, E> Links for IndexVec<L, E>
-where
-    E: LinkElem<LinkIndex = L>,
-    L: Idx,
-{
-    type LinkIndex = L;
-
-    fn next(links: &Self, index: L) -> Option<L> {
-        <E as LinkElem>::next(&links[index])
-    }
-}