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Optimise and_conditional_maps when using meet #22253

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Merged
hauntsaninja merged 1 commit into from
Oct 21, 2026
Merged

Optimise and_conditional_maps when using meet #22253

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13 changes: 4 additions & 9 deletions mypy/checker.py
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Original file line number Diff line number Diff line change
Expand Up @@ -9081,7 +9081,10 @@ def and_conditional_maps(m1: TypeMap, m2: TypeMap, *, use_meet: bool = False) ->
result[e1] = m1[e1]
continue

if not use_meet:
if use_meet:
e2 = m2_exprs[e1_hash]
result[e1] = meet_types(m1[e1], m2[e2])
else:
# If use_meet=False and the same expression's type is refined by both conditions,
# we somewhat arbitrarily give precedence to m2, unless a) m1's value is Never, or
# b) m2's value is Any and m1 isn't a union that could have been narrowed to Any.
Expand All @@ -9098,14 +9101,6 @@ def and_conditional_maps(m1: TypeMap, m2: TypeMap, *, use_meet: bool = False) ->
):
result[e1] = t1

if use_meet:
# For now, meet common keys only if specifically requested.
# This is currently used for tuple types narrowing, where having
# a precise result is important.
for e1 in m1:
for e2 in m2:
if literal_hash(e1) == literal_hash(e2):
result[e1] = meet_types(m1[e1], m2[e2])
return result


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