From f2d0304537616dc5c13e038935939bfdb813f17c Mon Sep 17 00:00:00 2001
From: Julian R <56316686+julianmrodri@users.noreply.github.com>
Date: Mon, 13 Jul 2020 19:13:30 -0300
Subject: [PATCH] feat: use extcodesize for isContract to reduce gas

---
 contracts/utils/Address.sol | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/contracts/utils/Address.sol b/contracts/utils/Address.sol
index 1d952cc0777..fe3ba653709 100644
--- a/contracts/utils/Address.sol
+++ b/contracts/utils/Address.sol
@@ -24,14 +24,14 @@ library Address {
      * ====
      */
     function isContract(address account) internal view returns (bool) {
-        // According to EIP-1052, 0x0 is the value returned for not-yet created accounts
-        // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
-        // for accounts without code, i.e. `keccak256('')`
-        bytes32 codehash;
-        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
+        // This method relies in extcodesize, which returns 0 for contracts in
+        // construction, since the code is only stored at the end of the
+        // constructor execution.
+
+        uint256 size;
         // solhint-disable-next-line no-inline-assembly
-        assembly { codehash := extcodehash(account) }
-        return (codehash != accountHash && codehash != 0x0);
+        assembly { size := extcodesize(account) }
+        return size > 0;
     }
 
     /**