Add disjoint
#559
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Add disjoint
#559
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...to improve the readability of the generated code.
sjakobi
commented
Nov 27, 2025
| disjointSubtrees _s _a Empty = True | ||
| disjointSubtrees s a (Leaf hB (L kB _)) = | ||
| lookupCont (\_ -> True) (\_ _ -> False) hB kB s a | ||
| disjointSubtrees s a b@Collision{} = disjointSubtrees s b a |
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Unfortunately GHC fails to specialize this and we end up with stuff like
disjoint_$s$wdisjointSubtrees @a @b @Int bx bx1 ww $fEqInt wild
or
disjoint_$s$wdisjointSubtrees @a @b @String bx bx1 ww $fEqList_$s$fEqList1 wild
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I misunderstood.
This function seems to be the result of case liberation (EDIT: it's not, it's due to -fspec-constr):
disjoint_$s$wdisjointSubtrees [Occ=LoopBreaker]
:: forall b a k.
Word#
-> SmallArray# (Leaf k a) -> Int# -> Eq k => HashMap k b -> Bool
and I suspect the specialization failure is related to the Eq dict being tucked in the middle of the other parameters instead of being first.
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I can replicate the issue with -O1 -fspec-constr.
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I have made a GHC issue: https://gitlab.haskell.org/ghc/ghc/-/issues/26615
lookupCont can do the work
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