From cb3b3cf6abcd29f408b28cf3d59489a22ccc8897 Mon Sep 17 00:00:00 2001
From: Yuki Okushi <yuki.okushi@huawei.com>
Date: Fri, 18 Jun 2021 18:22:41 +0900
Subject: Improve `get_by_key_enumerated` more

---
 .../src/sorted_map/index_map.rs                    | 42 ++++------------------
 .../rustc_data_structures/src/sorted_map/tests.rs  |  6 ++--
 compiler/rustc_middle/src/ty/assoc.rs              |  2 +-
 3 files changed, 11 insertions(+), 39 deletions(-)

diff --git a/compiler/rustc_data_structures/src/sorted_map/index_map.rs b/compiler/rustc_data_structures/src/sorted_map/index_map.rs
index 65689ab769c..2054f5eebf5 100644
--- a/compiler/rustc_data_structures/src/sorted_map/index_map.rs
+++ b/compiler/rustc_data_structures/src/sorted_map/index_map.rs
@@ -1,6 +1,5 @@
 //! A variant of `SortedMap` that preserves insertion order.
 
-use std::borrow::Borrow;
 use std::hash::{Hash, Hasher};
 use std::iter::FromIterator;
 
@@ -76,11 +75,7 @@ impl<I: Idx, K: Ord, V> SortedIndexMultiMap<I, K, V> {
     ///
     /// If there are multiple items that are equivalent to `key`, they will be yielded in
     /// insertion order.
-    pub fn get_by_key<Q: 'a>(&'a self, key: &Q) -> impl 'a + Iterator<Item = &'a V>
-    where
-        Q: Ord + ?Sized,
-        K: Borrow<Q>,
-    {
+    pub fn get_by_key(&'a self, key: K) -> impl 'a + Iterator<Item = &'a V> {
         self.get_by_key_enumerated(key).map(|(_, v)| v)
     }
 
@@ -89,35 +84,12 @@ impl<I: Idx, K: Ord, V> SortedIndexMultiMap<I, K, V> {
     ///
     /// If there are multiple items that are equivalent to `key`, they will be yielded in
     /// insertion order.
-    pub fn get_by_key_enumerated<Q>(&self, key: &Q) -> impl '_ + Iterator<Item = (I, &V)>
-    where
-        Q: Ord + ?Sized,
-        K: Borrow<Q>,
-    {
-        match self.binary_search_idx(key) {
-            Err(_) => self.idxs_to_items_enumerated(&[]),
-
-            Ok(idx) => {
-                let start = self.idx_sorted_by_item_key[..idx]
-                    .partition_point(|&i| self.items[i].0.borrow() != key);
-                let end = idx
-                    + self.idx_sorted_by_item_key[idx..]
-                        .partition_point(|&i| self.items[i].0.borrow() == key);
-                self.idxs_to_items_enumerated(&self.idx_sorted_by_item_key[start..end])
-            }
-        }
-    }
-
-    fn binary_search_idx<Q>(&self, key: &Q) -> Result<usize, usize>
-    where
-        Q: Ord + ?Sized,
-        K: Borrow<Q>,
-    {
-        self.idx_sorted_by_item_key.binary_search_by(|&idx| self.items[idx].0.borrow().cmp(key))
-    }
-
-    fn idxs_to_items_enumerated(&'a self, idxs: &'a [I]) -> impl 'a + Iterator<Item = (I, &'a V)> {
-        idxs.iter().map(move |&idx| (idx, &self.items[idx].1))
+    pub fn get_by_key_enumerated(&'a self, key: K) -> impl '_ + Iterator<Item = (I, &V)> {
+        let lower_bound = self.idx_sorted_by_item_key.partition_point(|&i| self.items[i].0 < key);
+        self.idx_sorted_by_item_key[lower_bound..]
+            .iter()
+            .take_while(move |&&i| self.items[i].0.eq(&key))
+            .map(move |&idx| (idx, &self.items[idx].1))
     }
 }
 
diff --git a/compiler/rustc_data_structures/src/sorted_map/tests.rs b/compiler/rustc_data_structures/src/sorted_map/tests.rs
index 7d91e1fdcef..1e977d709f1 100644
--- a/compiler/rustc_data_structures/src/sorted_map/tests.rs
+++ b/compiler/rustc_data_structures/src/sorted_map/tests.rs
@@ -14,11 +14,11 @@ fn test_sorted_index_multi_map() {
     }
 
     // `get_by_key` works.
-    assert_eq!(set.get_by_key(&3).copied().collect::<Vec<_>>(), vec![0]);
-    assert!(set.get_by_key(&4).next().is_none());
+    assert_eq!(set.get_by_key(3).copied().collect::<Vec<_>>(), vec![0]);
+    assert!(set.get_by_key(4).next().is_none());
 
     // `get_by_key` returns items in insertion order.
-    let twos: Vec<_> = set.get_by_key_enumerated(&2).collect();
+    let twos: Vec<_> = set.get_by_key_enumerated(2).collect();
     let idxs: Vec<usize> = twos.iter().map(|(i, _)| *i).collect();
     let values: Vec<usize> = twos.iter().map(|(_, &v)| v).collect();
 
diff --git a/compiler/rustc_middle/src/ty/assoc.rs b/compiler/rustc_middle/src/ty/assoc.rs
index d005f63ed43..2d177551664 100644
--- a/compiler/rustc_middle/src/ty/assoc.rs
+++ b/compiler/rustc_middle/src/ty/assoc.rs
@@ -124,7 +124,7 @@ impl<'tcx> AssocItems<'tcx> {
         &self,
         name: Symbol,
     ) -> impl '_ + Iterator<Item = &ty::AssocItem> {
-        self.items.get_by_key(&name).copied()
+        self.items.get_by_key(name).copied()
     }
 
     /// Returns an iterator over all associated items with the given name.
-- 
cgit 1.4.1-3-g733a5