fix #26131, unsound updating of variable upper bounds in subtyping #26737
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| if (jl_subtype(a, b)) return a; | ||
| if (jl_subtype(b, a)) return b; | ||
| } | ||
| return b; |
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Would it make sense to use an arbitrary total ordering on types to consistently decide which one of a and b to return in this case? It seems like it might be beneficial if simple_meet(a, b) == simple_meet(b, a) was guaranteed.
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Perhaps, but I think for now developing such an ordering is more trouble than it's worth. Presumably the ordering would be structural, which means that substituting an equal type with a different representation can still change results, which is not all that different from just picking the second argument here. We have also gotten by pretty well with just simple_meet(a,b) = b :)
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