main.d

module main;

import std.stdio;

interface A  {}
class B(T) : A
{
private:
  T val;
public:
	this(T val_)
	{
		val = val_;
	}
}


int main(string[] argv)
{
	auto b = B!(uint)(7);

	writeln("Hello D-World!");
	readln();
	return 0;
}

output.txt

Building Debug\ConsoleApp8.exe...
main.d(20): Error: no property 'opCall' for type 'main.B!(uint).B'