uma/packages/core/contracts/data-verification-mechanism/implementation/VotingToken.sol

// SPDX-License-Identifier: AGPL-3.0-only
pragma solidity ^0.8.0;

import "../../common/implementation/ExpandedERC20.sol";
import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Snapshot.sol";

/**
 * @title Ownership of this token allows a voter to respond to price requests.
 * @dev Supports snapshotting and allows the Oracle to mint new tokens as rewards.
 */
contract VotingToken is ExpandedERC20, ERC20Snapshot {
    /**
     * @notice Constructs the VotingToken.
     */
    constructor() ExpandedERC20("UMA Voting Token v1", "UMA", 18) ERC20Snapshot() {}

    function decimals() public view virtual override(ERC20, ExpandedERC20) returns (uint8) {
        return super.decimals();
    }

    /**
     * @notice Creates a new snapshot ID.
     * @return uint256 Thew new snapshot ID.
     */
    function snapshot() external returns (uint256) {
        return _snapshot();
    }

    // _transfer, _mint and _burn are ERC20 internal methods that are overridden by ERC20Snapshot,
    // therefore the compiler will complain that VotingToken must override these methods
    // because the two base classes (ERC20 and ERC20Snapshot) both define the same functions

    function _transfer(
        address from,
        address to,
        uint256 value
    ) internal override(ERC20) {
        super._transfer(from, to, value);
    }

    function _mint(address account, uint256 value) internal virtual override(ERC20) {
        super._mint(account, value);
    }

    function _burn(address account, uint256 value) internal virtual override(ERC20) {
        super._burn(account, value);
    }

    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual override(ERC20, ERC20Snapshot) {
        super._beforeTokenTransfer(from, to, amount);
    }
}