Playground

import System;

into namespace Bank
{
	public exception InsufficientFunds
	{
		public:
			i32 Missing;

			new(i32 missing) : base("insufficient funds")
			{
				Missing = missing;
			}
	}

	Withdraw(i32 balance, i32 amount) : i32
	{
		if (amount > balance)
			throw new InsufficientFundsException(amount - balance);
		return balance - amount;
	}

	Main()
	{
		try
		{
			Console.WriteLine(Withdraw(30, 10));
			Console.WriteLine(Withdraw(10, 25));
		}
		catch (InsufficientFundsException e)
		{
			Console.WriteLine(e.Message + ": " + e.Missing + " missing");
		}
		finally
		{
			Console.WriteLine("done");
		}
	}
}