Merge upstream openzeppelin-contracts into upstream-patched

CHANGELOG.md

 # Changelog
 
 ## Unreleased
+ * Enumerables: Improve gas cost of removal in `EnumerableSet` and `EnumerableMap`.
+ * Enumerables: Improve gas cost of lookup in `EnumerableSet` and `EnumerableMap`.
+
+## Unreleased
 
  * `IERC20Metadata`: add a new extended interface that includes the optional `name()`, `symbol()` and `decimals()` functions. ([#2561](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2561))
  * `ERC777`: make reception acquirement optional in `_mint`. ([#2552](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2552))

contracts/utils/structs/EnumerableSet.sol

@@ -81,15 +81,14 @@ library EnumerableSet {
             uint256 toDeleteIndex = valueIndex - 1;
             uint256 lastIndex = set._values.length - 1;
 
-            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
-            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.
+            if (lastIndex != toDeleteIndex) {
+                bytes32 lastvalue = set._values[lastIndex];
 
-            bytes32 lastvalue = set._values[lastIndex];
-
-            // Move the last value to the index where the value to delete is
-            set._values[toDeleteIndex] = lastvalue;
-            // Update the index for the moved value
-            set._indexes[lastvalue] = valueIndex; // Replace lastvalue's index to valueIndex
+                // Move the last value to the index where the value to delete is
+                set._values[toDeleteIndex] = lastvalue;
+                // Update the index for the moved value
+                set._indexes[lastvalue] = valueIndex; // Replace lastvalue's index to valueIndex
+            }
 
             // Delete the slot where the moved value was stored
             set._values.pop();
@@ -128,7 +127,6 @@ library EnumerableSet {
     * - `index` must be strictly less than {length}.
     */
     function _at(Set storage set, uint256 index) private view returns (bytes32) {
-        require(set._values.length > index, "EnumerableSet: index out of bounds");
         return set._values[index];
     }
 

docs/modules/ROOT/pages/erc721.adoc

@@ -16,7 +16,6 @@ Here's what a contract for tokenized items might look like:
 // SPDX-License-Identifier: MIT
 pragma solidity ^0.8.0;
 
-import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
 import "@openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol";
 import "@openzeppelin/contracts/utils/Counters.sol";
 
@@ -41,7 +40,7 @@ contract GameItem is ERC721URIStorage {
 }
 ----
 
-The xref:api:token/ERC721.adoc#ERC721[`ERC721`] contract includes all standard extensions (xref:api:token/ERC721.adoc#IERC721Metadata[`IERC721Metadata`] and xref:api:token/ERC721.adoc#IERC721Enumerable[`IERC721Enumerable`]). That's where the xref:api:token/ERC721.adoc#ERC721-_setTokenURI-uint256-string-[`_setTokenURI`] method comes from: we use it to store an item's metadata.
+The xref:api:token/ERC721.adoc#ERC721URIStorage[`ERC721URIStorage`] contract is an implementation of ERC721 that includes all standard extensions (xref:api:token/ERC721.adoc#IERC721Metadata[`IERC721Metadata`] and xref:api:token/ERC721.adoc#IERC721Enumerable[`IERC721Enumerable`]). That's where the xref:api:token/ERC721.adoc#ERC721-_setTokenURI-uint256-string-[`_setTokenURI`] method comes from: we use it to store an item's metadata.
 
 Also note that, unlike ERC20, ERC721 lacks a `decimals` field, since each token is distinct and cannot be partitioned.
 

test/utils/structs/EnumerableSet.behavior.js

@@ -51,7 +51,7 @@ function shouldBehaveLikeSet (valueA, valueB, valueC) {
 
   describe('at', function () {
     it('reverts when retrieving non-existent elements', async function () {
-      await expectRevert(this.set.at(0), 'EnumerableSet: index out of bounds');
+      await expectRevert.unspecified(this.set.at(0));
     });
   });