Simple casting?

[Taylor R Hillegeist via Digitalmars-d-learn]

I'm attempting to do a segment group.

details:
alias ProbePoint[3]=triple;
triple[] irqSortedSet = UniqueTriples.keys
                                .sort!("a[1].irqid < 
b[1].irqid",SwapStrategy.stable)
                                .array;         
83:triple[][] irqSortedSets = irqSortedSet.chunkBy!((a,b) => 
a[1].irqid == b[1].irqid);	


GetAllTriplesExtractFileIrqSplit.d(83): Error: cannot implicitly 
convert expression `chunkBy(irqSortedSet)` of type 
`ChunkByImpl!(__lambda4, ProbePoint[3][])` to `ProbePoint[3][][]`

I have something that looks like a triple[][] but I can't seem to 
get that type out.
when I add .array it converts to a Group which doesn't make sense 
to me because I'm not using a unary comparison. Any thought?