Use less common slot for EOA implementation (#69)

* set EOA implementation slot to deaddeaddead....

* fix tests

packages/contracts/contracts/optimistic-ethereum/OVM/accounts/OVM_ProxyEOA.sol

@@ -11,6 +11,8 @@ import { Lib_SafeExecutionManagerWrapper } from "../../libraries/wrappers/Lib_Sa
  */
 contract OVM_ProxyEOA {
 
+    bytes32 constant IMPLEMENTATION_KEY = 0xdeaddeaddeaddeaddeaddeaddeaddeaddeaddeaddeaddeaddeaddeaddeaddead;
+
     /***************
      * Constructor *
      ***************/
@@ -72,7 +74,7 @@ contract OVM_ProxyEOA {
     {
         return address(uint160(uint256(
             Lib_SafeExecutionManagerWrapper.safeSLOAD(
-                bytes32(uint256(0))
+                IMPLEMENTATION_KEY
             )
         )));
     }
@@ -87,7 +89,7 @@ contract OVM_ProxyEOA {
         internal
     {
         Lib_SafeExecutionManagerWrapper.safeSSTORE(
-            bytes32(uint256(0)),
+            IMPLEMENTATION_KEY,
             bytes32(uint256(uint160(_implementation)))
         );
     }

packages/contracts/test/contracts/OVM/accounts/OVM_ProxyEOA.spec.ts

@@ -100,6 +100,7 @@ describe('OVM_ProxyEOA', () => {
     })
   })
   describe('upgrade()', () => {
+    const implSlotKey = '0xdeaddeaddeaddeaddeaddeaddeaddeaddeaddeaddeaddeaddeaddeaddeaddead'
     it(`should upgrade the proxy implementation`, async () => {
       const newImpl = `0x${'81'.repeat(20)}`
       const newImplBytes32 = addrToBytes32(newImpl)
@@ -108,7 +109,7 @@ describe('OVM_ProxyEOA', () => {
       ])
       const ovmSSTORE: any =
         Mock__OVM_ExecutionManager.smocked.ovmSSTORE.calls[0]
-      expect(ovmSSTORE._key).to.equal(`0x${'00'.repeat(32)}`)
+      expect(ovmSSTORE._key).to.equal(implSlotKey)
       expect(ovmSSTORE._value).to.equal(newImplBytes32)
     })
     it(`should not allow upgrade of the proxy implementation by another account`, async () => {

packages/contracts/test/contracts/OVM/execution/OVM_ExecutionManager/ovmCREATEEOA.spec.ts

@@ -65,7 +65,7 @@ const test_ovmCREATEEOA: TestDefinition = {
             address: '0x17ec8597ff92C3F44523bDc65BF0f1bE632917ff',
           },
           expectedReturnStatus: true,
-          expectedReturnValue: 1619,
+          expectedReturnValue: 1682,
         },
       ],
     },