addressing the memory leak issue in EnumerableMap

contracts/mocks/EnumerableMapMock.sol

@@ -34,7 +34,15 @@ contract EnumerableMapMock {
     }
 
 
+    function tryGet(uint256 key) public view returns (bool, address) {
+        return _map.tryGet(key);
+    }
+
     function get(uint256 key) public view returns (address) {
         return _map.get(key);
     }
+
+    function getWithMessage(uint256 key, string calldata errorMessage) public view returns (address) {
+        return _map.get(key, errorMessage);
+    }
 }

contracts/utils/EnumerableMap.sol

@@ -143,6 +143,16 @@ library EnumerableMap {
         return (entry._key, entry._value);
     }
 
+    /**
+     * @dev Tries to returns the value associated with `key`.  O(1).
+     * Does not revert if `key` is not in the map.
+     */
+    function _tryGet(Map storage map, bytes32 key) private view returns (bool, bytes32) {
+        uint256 keyIndex = map._indexes[key];
+        if (keyIndex == 0) return (false, 0); // Equivalent to contains(map, key)
+        return (true, map._entries[keyIndex - 1]._value); // All indexes are 1-based
+    }
+
     /**
      * @dev Returns the value associated with `key`.  O(1).
      *
@@ -151,7 +161,9 @@ library EnumerableMap {
      * - `key` must be in the map.
      */
     function _get(Map storage map, bytes32 key) private view returns (bytes32) {
-        return _get(map, key, "EnumerableMap: nonexistent key");
+        uint256 keyIndex = map._indexes[key];
+        require(keyIndex != 0, "EnumerableMap: nonexistent key"); // Equivalent to contains(map, key)
+        return map._entries[keyIndex - 1]._value; // All indexes are 1-based
     }
 
     /**
@@ -217,6 +229,15 @@ library EnumerableMap {
         return (uint256(key), address(uint160(uint256(value))));
     }
 
+    /**
+     * @dev Tries to returns the value associated with `key`.  O(1).
+     * Does not revert if `key` is not in the map.
+     */
+    function tryGet(UintToAddressMap storage map, uint256 key) internal view returns (bool, address) {
+        (bool success, bytes32 value) = _tryGet(map._inner, bytes32(key));
+        return (success, address(uint160(uint256(value))));
+    }
+
     /**
      * @dev Returns the value associated with `key`.  O(1).
      *

test/utils/EnumerableMap.test.js

@@ -1,4 +1,4 @@
-const { BN, expectEvent } = require('@openzeppelin/test-helpers');
+const { BN, constants, expectEvent, expectRevert } = require('@openzeppelin/test-helpers');
 const { expect } = require('chai');
 
 const zip = require('lodash.zip');
@@ -139,4 +139,44 @@ contract('EnumerableMap', function (accounts) {
       expect(await this.map.contains(keyB)).to.equal(false);
     });
   });
+
+  describe('read', function () {
+    beforeEach(async function () {
+      await this.map.set(keyA, accountA);
+    });
+
+    describe('get', function () {
+      it('existing value', async function () {
+        expect(await this.map.get(keyA)).to.be.equal(accountA);
+      });
+      it('missing value', async function () {
+        await expectRevert(this.map.get(keyB), "EnumerableMap: nonexistent key");
+      });
+    });
+
+    describe('get with message', function () {
+      it('existing value', async function () {
+        expect(await this.map.getWithMessage(keyA, "custom error string")).to.be.equal(accountA);
+      });
+      it('missing value', async function () {
+        await expectRevert(this.map.getWithMessage(keyB, "custom error string"), "custom error string");
+      });
+    });
+
+    describe('tryGet', function () {
+      it('existing value', async function () {
+        expect(await this.map.tryGet(keyA)).to.be.deep.equal({
+          '0': true,
+          '1': accountA
+        });
+      });
+      it('missing value', async function () {
+        expect(await this.map.tryGet(keyB)).to.be.deep.equal({
+          '0': false,
+          '1': constants.ZERO_ADDRESS
+        });
+      });
+    });
+
+  });
 });