See the following code for CT error.
It seems we cannot take address of auto-return function declared in outside module, but we can if it's declared in the same module. 
The CT error is: "Error: forward reference"


file main.d:
----
import fun;

void run3(Fun,T...)(Fun fun,T args){
	fun(args);
}

class A1{
	void fun1(double x){
	}
	double fun2(double x){
		return x;
	}
	auto fun3(double x){
		return x;
	}
	auto fun4(double x){
	}
}

void main(){
	test1;
	test2;
}
void test1(){
	auto a=new A1;
	run3(&a.fun1,1);
	run3(&a.fun2,1);
	run3(&a.fun3,1);
	run3(&a.fun4,1);
}

void test2(){
	auto a=new A2;
	run3(&a.fun1,1);
	run3(&a.fun2,1);
	run3(&a.fun3,1);//CT error
	run3(&a.fun4,1);//CT error
}


-----

file fun.d:
----
module fun;

class A2{
	void fun1(double x){
	}
	double fun2(double x){
		return x;
	}
	auto fun3(double x){
		return x;
	}
	auto fun4(double x){
	}
}
----