Implement ERC1404 (extention of ERC20)

contracts/token/ERC20/ERC1404.sol

@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "./ERC20.sol";
+import "./IERC1404.sol";
+import "../../utils/Strings.sol";
+
+/**
+ * @title ERC-1404: Simple Restricted Token Standard
+ * @dev see https://github.com/ethereum/eips/issues/1404
+ */
+abstract contract ERC1404 is ERC20, IERC1404 {
+    /**
+     * @dev Implement transfer restriction codes. Override this function to
+     * implement your restriction policy.
+     */
+    function detectTransferRestriction(address /*from*/, address /*to*/, uint256 /*amount*/) public virtual override view returns (uint8) {
+        return uint8(0);
+    }
+
+    /**
+     * @dev Provides error messages for each restriction codes. Override this
+     * function to return meaningfull revert reasons.
+     */
+    function messageForTransferRestriction(uint8 restrictionCode) public virtual override view returns (string memory) {
+        return string(abi.encodePacked("ERC1404: Transfer restriction with code ", Strings.toString(uint256(restrictionCode))));
+    }
+
+    /**
+     * @dev See {ERC20-_beforeTokenTransfer}.
+     *
+     * Requirements:
+     *
+     * - transfer must abide by the transfer restriction rules.
+     */
+    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual override {
+        uint8 restrictionCode = detectTransferRestriction(from, to, amount);
+        if (restrictionCode != uint8(0)) {
+            revert(messageForTransferRestriction(restrictionCode));
+        }
+        super._beforeTokenTransfer(from, to, amount);
+    }
+}

contracts/token/ERC20/IERC1404.sol

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+// SPDX-License-Identifier: MIT
+
+pragma solidity >=0.6.0 <0.9.0;
+
+import "./IERC20.sol";
+
+/**
+ * @dev Interface of the ERC1404 standard as defined in the EIP.
+ */
+interface IERC1404 is IERC20 {
+    function detectTransferRestriction(address from, address to, uint256 amount) external view returns (uint8);
+    function messageForTransferRestriction(uint8 restrictionCode) external view returns (string memory);
+}