As of 2.049 ElementType is defined as follows:

template ElementType2(R)
{
    //alias typeof({ R r; return front(r[]); }()) ElementType;
    static if (is(typeof({return R.init.front();}()) T))
        alias T ElementType;
    else
        alias void ElementType;
}

However, the only function required of output ranges is: put(r, e)

Here is a simple test case using std.algorithm.copy and std.range.appender

import std.range;
import std.algorithm;

void main(string[] args) {
    string  str;
    copy("hello world",appender(&str));
    return;
}