From f2112be4d8e2b8798f789b948f2a7625b2350fe7 Mon Sep 17 00:00:00 2001
From: Hadrien Croubois <hadrien.croubois@gmail.com>
Date: Thu, 4 Feb 2021 21:28:13 +0100
Subject: [PATCH] Add revert string to Counter decrement overflow (#2500)

---
 contracts/utils/Counters.sol | 10 ++++++++--
 test/utils/Counters.test.js  |  2 +-
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/contracts/utils/Counters.sol b/contracts/utils/Counters.sol
index c4ee7b718..746a2631e 100644
--- a/contracts/utils/Counters.sol
+++ b/contracts/utils/Counters.sol
@@ -23,10 +23,16 @@ library Counters {
     }
 
     function increment(Counter storage counter) internal {
-        counter._value += 1;
+        unchecked {
+            counter._value += 1;
+        }
     }
 
     function decrement(Counter storage counter) internal {
-        counter._value = counter._value - 1;
+        uint256 value = counter._value;
+        require(value > 0, "Counter: decrement overflow");
+        unchecked {
+            counter._value = value - 1;
+        }
     }
 }
diff --git a/test/utils/Counters.test.js b/test/utils/Counters.test.js
index 5e6424e0e..90a1ae845 100644
--- a/test/utils/Counters.test.js
+++ b/test/utils/Counters.test.js
@@ -43,7 +43,7 @@ contract('Counters', function (accounts) {
 
       it('reverts if the current value is 0', async function () {
         await this.counter.decrement();
-        await expectRevert.unspecified(this.counter.decrement());
+        await expectRevert(this.counter.decrement(), 'Counter: decrement overflow');
       });
     });
     context('after incremented to 3', function () {