weird behavior returning delegate

[Carlos Santander]

This code, with DMD 0.162 on Windows:

//-----------------------
T delegate (T) acc (T) (T n)
{
	return (T i) { return n += i; };
}

void foo ()
{
	auto acc1 = acc (4);
	assert (5 == acc1 (1), "5 != 5");
	assert (7 == acc1 (2), "7 != 7");

	auto acc2 = acc (10);
	assert (11 == acc2 (1), "11 != 11");
	assert (12 == acc2 (1), "12 != 12");

	assert (10 == acc1 (3), "10 != 10"); // 16
	assert (20 == acc2 (8), "20 != 20");
}

import std.stdio;

void bar ()
{
	auto acc1 = acc (4);
	writefln (" 5 == %s", acc1 (1));
	writefln (" 7 == %s", acc1 (2));

	auto acc2 = acc (10);
	writefln ("11 == %s", acc2 (1));
	writefln ("12 == %s", acc2 (1));

	writefln ("10 == %s", acc1 (3));
	writefln ("20 == %s", acc2 (8));
	writefln ();
}

void main()
{
	bar ();
	foo ();
}
//-----------------------

Produces this:

  5 == 5
  7 == 10
11 == 11
12 == 9
10 == 13
20 == 17

Error: AssertError Failure test.d(16) 10 != 10

I think the assert failing is somewhat expected (stack frame no longer 
available), but how can the previous asserts work when the values shown with 
writefln are not the ones expected, or supposedly asserting correctly?

-- 
Carlos Santander Bernal