update comments

contracts/core/test/extensions/order_matcher.ts

@@ -11,6 +11,7 @@ import {
     txDefaults,
     web3Wrapper,
 } from '@0x/contracts-test-utils';
+import { artifacts as tokenArtifacts, DummyERC20TokenContract, DummyERC721TokenContract } from '@0x/contracts-tokens';
 import { BlockchainLifecycle } from '@0x/dev-utils';
 import { assetDataUtils } from '@0x/order-utils';
 import { RevertReason } from '@0x/types';
@@ -20,8 +21,6 @@ import * as chai from 'chai';
 import { LogWithDecodedArgs } from 'ethereum-types';
 import * as _ from 'lodash';
 
-import { DummyERC20TokenContract } from '../../generated-wrappers/dummy_erc20_token';
-import { DummyERC721TokenContract } from '../../generated-wrappers/dummy_erc721_token';
 import { ERC20ProxyContract } from '../../generated-wrappers/erc20_proxy';
 import { ERC721ProxyContract } from '../../generated-wrappers/erc721_proxy';
 import { ExchangeContract, ExchangeFillEventArgs } from '../../generated-wrappers/exchange';
@@ -444,7 +443,7 @@ describe('OrderMatcher', () => {
                 signedOrderLeft.signature,
                 signedOrderRight.signature,
             );
-            const logDecoder = new LogDecoder(web3Wrapper, artifacts);
+            const logDecoder = new LogDecoder(web3Wrapper, { ...artifacts, ...tokenArtifacts });
             const txReceipt = await logDecoder.getTxWithDecodedLogsAsync(
                 await web3Wrapper.sendTransactionAsync({
                     data,
@@ -457,6 +456,7 @@ describe('OrderMatcher', () => {
                 txReceipt.logs,
                 log => (log as LogWithDecodedArgs<ExchangeFillEventArgs>).event === 'Fill',
             );
+            // Only 2 Fill logs should exist for `matchOrders` call. `fillOrder` should not have been called and should not have emitted a Fill event.
             expect(fillLogs.length).to.be.equal(2);
         });
         it('should only take a spread in rightMakerAsset if entire leftMakerAssetSpread amount can be used to fill rightOrder after matchOrders call', async () => {
@@ -680,7 +680,7 @@ describe('OrderMatcher', () => {
         });
         it('should allow owner to withdraw ERC721 tokens', async () => {
             const erc721Token = await DummyERC721TokenContract.deployFrom0xArtifactAsync(
-                artifacts.DummyERC721Token,
+                tokenArtifacts.DummyERC721Token,
                 provider,
                 txDefaults,
                 constants.DUMMY_TOKEN_NAME,
@@ -725,7 +725,7 @@ describe('OrderMatcher', () => {
         });
         it('should be able to approve an ERC721 token by passing in allowance = 1', async () => {
             const erc721Token = await DummyERC721TokenContract.deployFrom0xArtifactAsync(
-                artifacts.DummyERC721Token,
+                tokenArtifacts.DummyERC721Token,
                 provider,
                 txDefaults,
                 constants.DUMMY_TOKEN_NAME,
@@ -742,7 +742,7 @@ describe('OrderMatcher', () => {
         });
         it('should be able to approve an ERC721 token by passing in allowance > 1', async () => {
             const erc721Token = await DummyERC721TokenContract.deployFrom0xArtifactAsync(
-                artifacts.DummyERC721Token,
+                tokenArtifacts.DummyERC721Token,
                 provider,
                 txDefaults,
                 constants.DUMMY_TOKEN_NAME,

contracts/extensions/contracts/OrderMatcher/MixinAssets.sol

@@ -20,8 +20,8 @@ pragma solidity 0.4.24;
 
 import "@0x/contracts-utils/contracts/utils/LibBytes/LibBytes.sol";
 import "@0x/contracts-utils/contracts/utils/Ownable/Ownable.sol";
-import "../../tokens/ERC20Token/IERC20Token.sol";
-import "../../tokens/ERC721Token/IERC721Token.sol";
+import "@0x/contracts-tokens/contracts/tokens/ERC20Token/IERC20Token.sol";
+import "@0x/contracts-tokens/contracts/tokens/ERC721Token/IERC721Token.sol";
 import "./mixins/MAssets.sol";
 import "./libs/LibConstants.sol";
 
@@ -98,6 +98,7 @@ contract MixinAssets is
     )
         internal
     {
+        // 4 byte id + 12 0 bytes before ABI encoded token address.
         address token = assetData.readAddress(16);
 
         // Transfer tokens.
@@ -149,7 +150,9 @@ contract MixinAssets is
             "INVALID_AMOUNT"
         );
         // Decode asset data.
+        // 4 byte id + 12 0 bytes before ABI encoded token address.
         address token = assetData.readAddress(16);
+        // 4 byte id + 32 byte ABI encoded token address before token id.
         uint256 tokenId = assetData.readUint256(36);
 
         // Perform transfer.

contracts/extensions/contracts/OrderMatcher/MixinMatchOrders.sol

@@ -230,7 +230,7 @@ contract MixinMatchOrders is
                     // | 932                       | a       | rightMakerAssetData Contents                |
                     // | 932 + a                   | 32      | rightTakerAssetData Length                  |
                     // | 964                       | b       | rightTakerAssetData Contents                |
-                    // | 964 + b                   | 32      | rightSigature Length (always 0)             |
+                    // | 964 + b                   | 32      | rightSignature Length (always 0)            |
 
                     // We assume that `leftOrder.makerAssetData == rightOrder.takerAssetData` and `leftOrder.takerAssetData == rightOrder.makerAssetData`
                     // `EXCHANGE.matchOrders` already makes this assumption, so it is likely
@@ -280,6 +280,7 @@ contract MixinMatchOrders is
                     )
                     mstore(rightSignatureStart, 0)
 
+                    // function selector (4 bytes) + 3 params (3 * 32 bytes) must be stored before `rightOrderStart`
                     let cdStart := sub(rightOrderStart, 100)
 
                     // `fillOrder` selector = 0xb4be83d5
@@ -288,7 +289,7 @@ contract MixinMatchOrders is
                     // Write offset to `rightOrder`
                     mstore(add(cdStart, 4), 96)
 
-                    // Write `takerAssetFillAmount`
+                    // Write `takerAssetFillAmount`, which will be the `leftMakerAssetSpreadAmount` received from the `matchOrders` call
                     mstore(add(cdStart, 36), mload(256))
 
                     // Write offset to `rightSignature`

contracts/extensions/contracts/OrderMatcher/interfaces/IMatchOrders.sol

@@ -19,7 +19,7 @@
 pragma solidity 0.4.24;
 pragma experimental ABIEncoderV2;
 
-import "../../../protocol/Exchange/libs/LibOrder.sol";
+import "@0x/contracts-libs/contracts/libs/LibOrder.sol";
 
 
 contract IMatchOrders {

contracts/extensions/contracts/OrderMatcher/interfaces/IOrderMatcher.sol

@@ -18,7 +18,7 @@
 
 pragma solidity 0.4.24;
 
-import "../../../utils/Ownable/IOwnable.sol";
+import "@0x/contract-utils/contracts/utils/Ownable/IOwnable.sol";
 import "./IMatchOrders.sol";
 import "./IAssets.sol";
 

contracts/extensions/contracts/OrderMatcher/libs/LibConstants.sol

@@ -18,7 +18,7 @@
 
 pragma solidity 0.4.24;
 
-import "../../../protocol/Exchange/interfaces/IExchange.sol";
+import "@0x/contracts-interfaces/contracts/protocol/Exchange/IExchange.sol";
 
 
 contract LibConstants {