This is an outdated statement:

"While a non-static nested class can access the stack variables of its enclosing function, that access becomes invalid once the enclosing function exits: 

class Base
{
    int foo() { return 1; }
}

Base func()
{   int m = 3;

    class Nested : Base
    {
	int foo() { return m; }
    }

    Base b = new Nested;

    assert(b.foo() == 3);	// Ok, func() is still active
    return b;
}

int test()
{
    Base b = func();
    return b.foo();		// Error, func().m is undefined
}
"

As is stated in TDPL, variables in the local function get allocated on the heap if DMD detects that a returning class needs access to it. This section needs to be updated.

The next section with the code example for a workaround can be removed:

"If this kind of functionality is needed, the way to make it work is to make copies of the needed variables within the nested class's constructor"