cannot call impure function ~this

[Namespace]

I get this error:
----
/d701/f223.d(11): Error: pure function 'f223.getA' cannot call 
impure function 'f223.A.~this'
----

with this code:
----
import std.stdio;

struct A {
public:
	~this() {
		writeln("DTor");
	}
}

A getA() pure nothrow {
	return A();
}

void main()
{
	A a = getA();
	
	writeln("end of main");
}
----

But without pure and nothrow I get this output:
----
end of main
DTor
----

Why the compiler thinks that the function should/could call 
A::~this?