求助：Solidity代码编译报ParserError错误，期望分号';'却得到关键字'contract'

Hey there! Let's break down why you're hitting this error and how to fix it.

The Root Cause #

Your code is mixing Solidity contract syntax with JavaScript test code (looks like Mocha/Truffle test syntax), which the Solidity compiler can't parse. When the compiler reads your pragma solidity ^0.5.0; line, it expects either a semicolon to end the line or a valid Solidity contract definition next—but instead it sees contract('Token', ([deployer, receiver]) => { which is JavaScript, not Solidity. That's why it throws the ParserError.

The Fix: Split Your Code into Two Files #

You need to separate your Solidity contract and your test code into distinct files, each using their own language's syntax.

1. Create a Solidity Contract File (Token.sol)

This is where you'll define your token contract using valid Solidity syntax:

pragma solidity ^0.5.0;

contract Token {
    // Public state variables for token details
    string public name;
    string public symbol;
    uint8 public decimals;
    uint256 public totalSupply;

    // Constructor runs when the contract is deployed
    constructor() public {
        name = "Arv Token";
        symbol = "ARVV";
        decimals = 18;
        // Calculate total supply with 18 decimals (1 token = 1e18 wei)
        totalSupply = 1000000 * (10 ** uint256(decimals));
    }
}

2. Create a JavaScript Test File (token.test.js)

Put your test logic here (this works for Truffle or Mocha-based testing environments):

const Token = artifacts.require("Token");

// Helper function to convert token amount to wei (matches 18 decimals)
function tokens(n) {
    return web3.utils.toWei(n.toString(), 'ether');
}

contract('Token', ([deployer, receiver]) => {
    const name = 'Arv Token';
    const symbol = 'ARVV';
    const decimals = 18;
    const totalSupply = tokens(1000000);
    let token;

    // Deploy a fresh token instance before each test
    beforeEach(async () => {
        token = await Token.new();
    });

    // Example test case to verify token details
    it('initializes the token with correct values', async () => {
        const tokenName = await token.name();
        assert.equal(tokenName, name, 'Token name matches');

        const tokenSymbol = await token.symbol();
        assert.equal(tokenSymbol, symbol, 'Token symbol matches');

        const tokenDecimals = await token.decimals();
        assert.equal(tokenDecimals.toString(), decimals.toString(), 'Decimals match');

        const tokenTotalSupply = await token.totalSupply();
        assert.equal(tokenTotalSupply.toString(), totalSupply, 'Total supply matches');
    });
});

Why This Works #

• The Solidity compiler only processes the .sol file, which now has valid contract syntax—no more parsing errors.
• The test file uses JavaScript syntax that your testing framework (like Truffle) understands, allowing you to deploy and test your contract correctly.

内容的提问来源于stack exchange，提问作者Christian