Returns true if a given expression was defined. bool __defined(expression); The __defined() function allows checking if a given declaration has been defined. It is useful when writing generic list-based code.

class Class1
{
	typedef logic[4] Type;
}

class Class2
{
	typedef logic[8] Type;
	const int Val = 5;
}

entity Test
{
	generate dummy foreach(any c in __list(Class1, Class2))
	{
		generate inner if (__defined(c.Val))
		{
			signal c.Type sig = c.Val;
		}
		else
		{
			signal c.Type sig;
		}
	}
}

Generated VHDL code:

entity Test is
end entity Test;

architecture Behavioral of Test is
	signal dummy_0_inner_case_2_sig : std_logic_vector(3 downto 0);
	signal dummy_1_inner_case_1_sig : std_logic_vector(7 downto 0) := X"05";
	
	begin
		
end architecture Behavioral;