@0x/contracts-utils: Use simple assembly instead of abi.decode() in LibERC20Token._callWithOptionalBooleanResult().

`@0x/contracts-exchange-forwarder`: Use `LibERC20Token` in `MixinAssets`.
`@0x/order-utils`: Remove `TransferFailedError` from `ForwarderRevertErrors`.

contracts/exchange-forwarder/CHANGELOG.json

@@ -1,4 +1,12 @@
 [
+    {
+        "changes": [
+            {
+                "note": "Use `LibERC20Token` in `MixinAssets`",
+                "pr": 2309
+            }
+        ]
+    },
     {
         "version": "3.1.0-beta.0",
         "changes": [

contracts/exchange-forwarder/contracts/src/MixinAssets.sol

@@ -19,6 +19,7 @@
 pragma solidity ^0.5.9;
 
 import "@0x/contracts-utils/contracts/src/LibBytes.sol";
+import "@0x/contracts-utils/contracts/src/LibERC20Token.sol";
 import "@0x/contracts-utils/contracts/src/LibRichErrors.sol";
 import "@0x/contracts-utils/contracts/src/Ownable.sol";
 import "@0x/contracts-erc20/contracts/src/interfaces/IERC20Token.sol";
@@ -105,38 +106,8 @@ contract MixinAssets is
         internal
     {
         address token = assetData.readAddress(16);
-
         // Transfer tokens.
-        // We do a raw call so we can check the success separate
-        // from the return data.
-        (bool success, bytes memory returnData) = token.call(abi.encodeWithSelector(
-            ERC20_TRANSFER_SELECTOR,
-            msg.sender,
-            amount
-        ));
-        if (!success) {
-            LibRichErrors.rrevert(LibForwarderRichErrors.TransferFailedError(returnData));
-        }
-
-        // Check return data.
-        // If there is no return data, we assume the token incorrectly
-        // does not return a bool. In this case we expect it to revert
-        // on failure, which was handled above.
-        // If the token does return data, we require that it is a single
-        // value that evaluates to true.
-        assembly {
-            if returndatasize {
-                success := 0
-                if eq(returndatasize, 32) {
-                    // First 64 bytes of memory are reserved scratch space
-                    returndatacopy(0, 0, 32)
-                    success := mload(0)
-                }
-            }
-        }
-        if (!success) {
-            LibRichErrors.rrevert(LibForwarderRichErrors.TransferFailedError(returnData));
-        }
+        LibERC20Token.transfer(token, msg.sender, amount);
     }
 
     /// @dev Decodes ERC721 assetData and transfers given amount to sender.

contracts/exchange-forwarder/contracts/src/libs/LibForwarderRichErrors.sol

@@ -51,10 +51,6 @@ library LibForwarderRichErrors {
     bytes4 internal constant OVERSPENT_WETH_ERROR_SELECTOR =
         0xcdcbed5d;
 
-    // bytes4(keccak256("TransferFailedError(bytes)"))
-    bytes4 internal constant TRANSFER_FAILED_ERROR_SELECTOR =
-        0x5e7eb60f;
-
     // bytes4(keccak256("DefaultFunctionWethContractOnlyError(address)"))
     bytes4 internal constant DEFAULT_FUNCTION_WETH_CONTRACT_ONLY_ERROR_SELECTOR =
         0x08b18698;
@@ -160,19 +156,6 @@ library LibForwarderRichErrors {
         );
     }
 
-    function TransferFailedError(
-        bytes memory errorData
-    )
-        internal
-        pure
-        returns (bytes memory)
-    {
-        return abi.encodeWithSelector(
-            TRANSFER_FAILED_ERROR_SELECTOR,
-            errorData
-        );
-    }
-
     function DefaultFunctionWethContractOnlyError(
         address senderAddress
     )

contracts/utils/contracts/src/LibERC20Token.sol

@@ -101,7 +101,8 @@ library LibERC20Token {
                 return;
             }
             if (resultData.length == 32) {
-                uint256 result = abi.decode(resultData, (uint256));
+                uint256 result;
+                assembly { result := mload(add(resultData, 0x20)) }
                 if (result == 1) {
                     return;
                 }

packages/order-utils/src/forwarder_revert_errors.ts

@@ -60,12 +60,6 @@ export class OverspentWethError extends RevertError {
     }
 }
 
-export class TransferFailedError extends RevertError {
-    constructor(errorData?: string) {
-        super('TransferFailedError', 'TransferFailedError(bytes errorData)', { errorData });
-    }
-}
-
 export class DefaultFunctionWethContractOnlyError extends RevertError {
     constructor(senderAddress?: string) {
         super('DefaultFunctionWethContractOnlyError', 'DefaultFunctionWethContractOnlyError(address senderAddress)', {