function getOpeningParenOfParams(node, sourceCode) {
	// If the node is an arrow function and doesn't have parens, this returns the identifier of the first param.
	if (node.type === "ArrowFunctionExpression" && node.params.length === 1) {
		const argToken = sourceCode.getFirstToken(node.params[0]);
		const maybeParenToken = sourceCode.getTokenBefore(argToken);

		return isOpeningParenToken(maybeParenToken)
			? maybeParenToken
			: argToken;
	}

	// Otherwise, returns paren.
	return node.id
		? sourceCode.getTokenAfter(node.id, isOpeningParenToken)
		: sourceCode.getFirstToken(node, isOpeningParenToken);
}
Gets the `(` token of the given function node.
@param {ASTNode} node The function node to get.
@param {SourceCode} sourceCode The source code object to get tokens.
@returns {Token} `(` token.