Avoiding construction of dead dictionaries

I have another optimization problem. ConCat includes this definition: (<+) :: Con a => (Con b => r) -> (a |- b) -> r r <+ Entail (Sub Dict) = r The right-hand argument of <+ leads to a dictionary construction that is a proof of a certain property, but the dictionary itself ends up being dead, like so: case $w$dOpCon_r2kGJ ... of { (# ww1_s27L3 #) -> ... } ^^^^^^^^^ never used Yet, ghc (8.10.4) never elides this code. (I'm naively assuming because of the unboxed tuple, but actually have no clue.) Is there any chance of convincing ghc of erasing the dictionary construction? Help would be much appreciated! -- Regards, Mike