import std.stdio;

char[] itoa(uint i) {
	if (i < 10) {
		return ""~cast(char)(i + 48);
	} else {
		uint i2 = i / 10;
		return itoa(i2)~cast(char)(i - i2*10 + 48);
	}
}

char[] trycast(int max) {
	char[] result = "";
	for (uint i = 0; i < max; i++)
		result ~= "if (cast(T["~itoa(i)~"])x !is null) { dg["~itoa(i)~"](); return; }";
	return result;
}

template check(T...) {
void check(Tx)(Tx x, void delegate()[] dg ...) {
	static if (is(Tx == T[0])) {
//		writefln("exact match");
        dg[0]();
    } else {
		mixin(trycast(T.length));

		throw new Exception("cast error");
    }
}
}

class TypeA0 { int id = 10; }
	class TypeA : TypeA0 { int id = 11; }
		class TypeA2 : TypeA { int id = 12; }
class TypeB { int id = 20; }

void main() {
	auto x = new TypeA;
	check!(TypeA, TypeB)(x, {writefln("TypeA id=%s", x.id);}, {writefln("TypeB id=%s", x.id);});
}