Merge branch 'master' into solc-0.7

contracts/utils/EnumerableSet.sol

@@ -23,8 +23,8 @@ pragma solidity ^0.7.0;
  * }
  * ```
  *
- * As of v3.0.0, only sets of type `address` (`AddressSet`) and `uint256`
- * (`UintSet`) are supported.
+ * As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)
+ * and `uint256` (`UintSet`) are supported.
  */
 library EnumerableSet {
     // To implement this library for multiple types with as little code
@@ -132,6 +132,60 @@ library EnumerableSet {
         return set._values[index];
     }
 
+    // Bytes32Set
+
+    struct Bytes32Set {
+        Set _inner;
+    }
+
+    /**
+     * @dev Add a value to a set. O(1).
+     *
+     * Returns true if the value was added to the set, that is if it was not
+     * already present.
+     */
+    function add(Bytes32Set storage set, bytes32 value) internal returns (bool) {
+        return _add(set._inner, value);
+    }
+
+    /**
+     * @dev Removes a value from a set. O(1).
+     *
+     * Returns true if the value was removed from the set, that is if it was
+     * present.
+     */
+    function remove(Bytes32Set storage set, bytes32 value) internal returns (bool) {
+        return _remove(set._inner, value);
+    }
+
+    /**
+     * @dev Returns true if the value is in the set. O(1).
+     */
+    function contains(Bytes32Set storage set, bytes32 value) internal view returns (bool) {
+        return _contains(set._inner, value);
+    }
+
+    /**
+     * @dev Returns the number of values in the set. O(1).
+     */
+    function length(Bytes32Set storage set) internal view returns (uint256) {
+        return _length(set._inner);
+    }
+
+   /**
+    * @dev Returns the value stored at position `index` in the set. O(1).
+    *
+    * Note that there are no guarantees on the ordering of values inside the
+    * array, and it may change when more values are added or removed.
+    *
+    * Requirements:
+    *
+    * - `index` must be strictly less than {length}.
+    */
+    function at(Bytes32Set storage set, uint256 index) internal view returns (bytes32) {
+        return _at(set._inner, index);
+    }
+
     // AddressSet
 
     struct AddressSet {