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Optimize tuple and map emptiness checks #15619

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Merged
josevalim merged 2 commits into from
Jul 16, 2026
Merged

Optimize tuple and map emptiness checks #15619

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7feaf6e
Optimize tuple emptiness checks
josevalim Jul 16, 2026
bc34a8f
Optimize maps too
josevalim Jul 16, 2026
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40 changes: 28 additions & 12 deletions lib/elixir/lib/module/types/descr.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -4432,13 +4432,22 @@ defmodule Module.Types.Descr do
end

defp map_line_meet_empty?(key, type, neg_type, t1, t2, tag, neg_tag, acc_meet, negs, seen) do
diff = bare_difference(type, neg_type)
meet = bare_intersection(type, neg_type)

(empty_seen?(diff, seen) or
map_line_empty?(tag, Enum.reverse(acc_meet, [{key, diff} | t1]), negs, seen)) and
(empty_seen?(meet, seen) or
map_line_meet_empty?(t1, t2, tag, neg_tag, [{key, meet} | acc_meet], negs, seen))
if empty_seen?(meet, seen) do
# This negative map is disjoint from the current line at this field.
map_line_empty?(tag, Enum.reverse(acc_meet, [{key, type} | t1]), negs, seen)
else
diff = bare_difference(type, neg_type)

if empty_seen?(diff, seen) do
# The field is a subtype of the negative field, so their intersection is type.
map_line_meet_empty?(t1, t2, tag, neg_tag, [{key, type} | acc_meet], negs, seen)
else
map_line_empty?(tag, Enum.reverse(acc_meet, [{key, diff} | t1]), negs, seen) and
map_line_meet_empty?(t1, t2, tag, neg_tag, [{key, meet} | acc_meet], negs, seen)
end
end
end

defp map_line_fields_empty?(
Expand Down Expand Up @@ -5001,15 +5010,22 @@ defmodule Module.Types.Descr do
# Handles the case where {tag, elements} is an open tuple, like {:open, []}
{ty, elements} = List.pop_at(elements, 0, term())

# In this case, there is no intersection between the positive and this negative.
# So we should just "go next"
diff = bare_difference(ty, neg_type)
meet = bare_intersection(ty, neg_type)

(empty_seen?(diff, seen) or
tuple_line_empty?(tag, Enum.reverse(acc_meet, [diff | elements]), negs, seen)) and
(empty_seen?(meet, seen) or
tuple_elements_empty?([meet | acc_meet], tag, elements, neg_elements, negs, seen))
if empty_seen?(meet, seen) do
# This negative tuple is disjoint from the current line at this element.
tuple_line_empty?(tag, Enum.reverse(acc_meet, [ty | elements]), negs, seen)
else
diff = bare_difference(ty, neg_type)

if empty_seen?(diff, seen) do
# The element is a subtype of the negative element, so their intersection is ty.
tuple_elements_empty?([ty | acc_meet], tag, elements, neg_elements, negs, seen)
else
tuple_line_empty?(tag, Enum.reverse(acc_meet, [diff | elements]), negs, seen) and
tuple_elements_empty?([meet | acc_meet], tag, elements, neg_elements, negs, seen)
end
end
end

# Determines if the set difference is empty when:
Expand Down
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