Preserve the intersection of disjoint numbers in match analysis #14550
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OlivierBlanvillain
approved these changes
Feb 24, 2022
SethTisue
approved these changes
Feb 24, 2022
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Very elegant that keeping I can't think of any other test coverage that should be added (even after discussing it with Dale, from every different angle either of us could think of). |
The use of provablyDisjoint is a way of simplifying an intersection of two types into the Empty space, using type comparing logic. However, for types like (42L: Long) and (it: Int) (a constant type and a term ref, of two different number types) the two types are provably disjoint, but that doesn't mean that a "case `it` =>" won't match a "42L" scrutinee. So we extend the logic to keep the intersection as it is when numeric value types are in play.
Rather than trying to fix the types such that subtyping returns true for these cases, we can rely on the numeric opt-out of using provablyDisjoint and extend it to boxed numerics.
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The use of provablyDisjoint is a way of simplifying an intersection of
two types into the Empty space, using type comparing logic. However,
for types like (42L: Long) and (it: Int) (a constant type and a term
ref, of two different number types) the two types are provably disjoint,
but that doesn't mean that a "case
it=>" won't match a "42L"scrutinee. So we extend the logic to keep the intersection as it is
when numeric value types are in play.
Closes #14407