Troubles with taskPool.amap, lambdas and more

[bearophile]

This Rosettacode code task (in two different D versions) seems to 
show some D/Phobos regressions (or just some problems):

http://rosettacode.org/wiki/Parallel_calculations#D

In the second version (that works with dmd 2.066alpha) I have had 
to comment out the pure nothrow here, despite this used to 
compile few months ago:

     this(in ulong n) /*pure nothrow*/ {
         super(&run);
         num = n;
         fac = new ulong[0];
     }


The situation with the first version is worse. This is a 
compilable first version (at the moment the first version on the 
site doesn't have a decompose() function):


import std.stdio, std.algorithm, std.parallelism, std.typecons;

ulong[] decompose(ulong n) pure nothrow {
     typeof(return) result;
     for (ulong i = 2; n >= i * i; i++)
         for (; n % i == 0; n /= i)
             result ~= i;
     if (n != 1)
         result ~= n;
     return result;
}

void main() {
     immutable ulong[] data = [
         2UL^^59-1, 2UL^^59-1, 2UL^^59-1, 112_272_537_195_293UL,
         115_284_584_522_153, 115_280_098_190_773,
         115_797_840_077_099, 112_582_718_962_171,
         112_272_537_095_293, 1_099_726_829_285_419];

     //auto factors = taskPool.amap!(n => tuple(decompose(n), 
n))(data);
     //static enum genPair = (ulong n) pure => tuple(decompose(n), 
n); // ?
     static genPair(ulong n) pure { return tuple(decompose(n), n); 
}
     auto factors = taskPool.amap!genPair(data);

     auto pairs = factors.map!(p => tuple(p[0].reduce!min, p[1]));
     writeln("N. with largest min factor: ", pairs.reduce!max[1]);
}


A problem (that is not a regression) is that taskPool.amap 
doesn't seem able to accept a lambda for some reason.

It can't accept the static enum lambda either, for other unknown 
reasons.

But even using a normal static inner function, the program 
asserts most times at run-time (but not always), while few months 
ago it used to work reliably. So perhaps in this messy situation 
there's some material for bug reports. Opinions and suggestions 
are welcome.

Bye,
bearophile