import std.exception, std.stdio;
 
struct CustomInteger(T, T minValue, T maxValue)
{
	T value_;
 
	alias value this;
 
	@property T value() const
	{
		enforce((value_ >= minValue) &&
				(value_ <= maxValue));
 
		return value_;
	}
 
	@property void value(T v)
	{
		value_ = v;
	}
}
 
void main()
{
	alias Balance = CustomInteger!(int, -32_000, 32_000);
 
	auto b = Balance(42);
 
	// b += 5; // Error: 'b += 5' is not a scalar,
	// it is a CustomInteger!(int, -32000, 32000)
 
	writeln(b); // 42
 
	b = 40_000;
 
	writeln(b); // object.Exception@acm.d(11): Enforcement failed
}

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