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Correct tuple difference comments #15859

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josevalim merged 1 commit into from
Sep 5, 2026
+4 −3
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Correct tuple difference comments #15859

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7 changes: 4 additions & 3 deletions lib/elixir/lib/module/types/descr.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -4954,14 +4954,15 @@ defmodule Module.Types.Descr do
end)
end

# Important: this generates DISJOINT tuples.
# Returns tuples whose union is the difference. The size and content
# branches may overlap.
defp tuple_eliminate_single_negation(tag, elements, {neg_tag, neg_elements}) do
n = length(elements)
m = length(neg_elements)

# Scenarios where the difference is guaranteed to be empty:
# Scenarios where the tuples are disjoint, so the positive tuple is unchanged:
# 1. When removing larger tuples from a fixed-size positive tuple
# 2. When removing smaller tuples from larger tuples
# 2. When removing smaller fixed-size tuples from larger tuples
# 3. When there is no intersection between the elements of the two tuples
if (tag == :closed and n < m) or (neg_tag == :closed and n > m) or
zip_empty_intersection?(elements, neg_elements) do
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