From f7f015257352135d4a5c61a7806bae0e9f05323c Mon Sep 17 00:00:00 2001
From: Lawrence Forman <lawrence@0xproject.com>
Date: Wed, 22 Apr 2020 15:07:44 -0400
Subject: [PATCH] `@0x/contracts-zero-ex`: Add `Unused` to `StorageId` enum

---
 contracts/zero-ex/contracts/src/features/Migrate.sol   | 2 +-
 contracts/zero-ex/contracts/src/features/Ownable.sol   | 2 +-
 contracts/zero-ex/contracts/src/storage/LibStorage.sol | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/contracts/zero-ex/contracts/src/features/Migrate.sol b/contracts/zero-ex/contracts/src/features/Migrate.sol
index 8bbc20cd6c..cc78fa1263 100644
--- a/contracts/zero-ex/contracts/src/features/Migrate.sol
+++ b/contracts/zero-ex/contracts/src/features/Migrate.sol
@@ -72,7 +72,7 @@ contract Migrate is
             // If the owner is already set to ourselves then we've reentered.
             _rrevert(LibMigrateRichErrors.AlreadyMigratingError());
         }
-        // Temporarily set the owner to ourselves.
+        // Temporarily set the owner to ourselves to enable admin functions.
         ownableStor.owner = address(this);
         stor.migrationOwner = prevOwner;
 
diff --git a/contracts/zero-ex/contracts/src/features/Ownable.sol b/contracts/zero-ex/contracts/src/features/Ownable.sol
index 609aecbfc6..1b8429434c 100644
--- a/contracts/zero-ex/contracts/src/features/Ownable.sol
+++ b/contracts/zero-ex/contracts/src/features/Ownable.sol
@@ -48,7 +48,7 @@ contract Ownable is
     /// @param impl the actual address of this feature contract.
     /// @return success Magic bytes if successful.
     function bootstrap(address impl) external returns (bytes4 success) {
-        // Set the owner.
+        // Set the owner to ourselves to allow bootstrappers to call `extend()`.
         LibOwnableStorage.getStorage().owner = address(this);
 
         // Register feature functions.
diff --git a/contracts/zero-ex/contracts/src/storage/LibStorage.sol b/contracts/zero-ex/contracts/src/storage/LibStorage.sol
index 403a1440c6..083f933a4f 100644
--- a/contracts/zero-ex/contracts/src/storage/LibStorage.sol
+++ b/contracts/zero-ex/contracts/src/storage/LibStorage.sol
@@ -30,6 +30,7 @@ library LibStorage {
 
     /// @dev Storage IDs for feature storage buckets.
     enum StorageId {
+        Unused, // Unused buffer for state accidents.
         Proxy,
         SimpleFunctionRegistry,
         Ownable,
@@ -44,7 +45,6 @@ library LibStorage {
         pure
         returns (uint256 offset)
     {
-        // We don't use safeMul here to save gas.
         // This should never overflow with a reasonable `STORAGE_OFFSET_MULTIPLIER`
         // because Solidity will do a range check on `storageId` during the cast.
         return uint256(storageId) * STORAGE_OFFSET_MULTIPLIER;