when using typedefs of structs
their constructors return the original type instead of the new type

struct Ca {
	this(int a) {
		_answer = a / 2;
	}

	int _answer;
}

void testClasses() {
	typedef Ca Da;

	Ca a = Ca(84);
	Da c = Da(84);
	
}

tests0.d(38):

Error: cannot implicitly convert expression (((Ca __ctmp276 = __ctmp276 = 0;
) , __ctmp276).this(84)) of type Ca to Da

A cast is required for the code to work.