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Fix inference with UninhabitedType by cdce8p · Pull Request #16994 · python/mypy · GitHub
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Fix inference with UninhabitedType #16994

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Merged
merged 4 commits into from
Mar 7, 2024
Merged

Fix inference with UninhabitedType #16994

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08154ab
Fix inference with UninhabitedType
cdce8p Mar 6, 2024
8ec9fc5
Use proper type
cdce8p Mar 6, 2024
d9e93e0
Add additional test cases
cdce8p Mar 6, 2024
cd4600f
Deal with edge case
cdce8p Mar 7, 2024
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Deal with edge case
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@cdce8p
cdce8p committed Mar 7, 2024
commit cd4600f5bf48db080307447a6eed2bce83da8b7a
4 changes: 2 additions & 2 deletions mypy/join.py
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Expand Up @@ -108,9 +108,9 @@ def join_instances(self, t: Instance, s: Instance) -> ProperType:
# TODO: contravariant case should use meet but pass seen instances as
# an argument to keep track of recursive checks.
elif type_var.variance in (INVARIANT, CONTRAVARIANT):
if isinstance(ta_proper, UninhabitedType):
if isinstance(ta_proper, UninhabitedType) and not ta_proper.is_noreturn:
new_type = sa
elif isinstance(sa_proper, UninhabitedType):
elif isinstance(sa_proper, UninhabitedType) and not sa_proper.is_noreturn:
new_type = ta
elif not is_equivalent(ta, sa):
self.seen_instances.pop()
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9 changes: 8 additions & 1 deletion test-data/unit/check-inference.test
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Expand Up @@ -3815,7 +3815,7 @@ reveal_type(Combine(m1, m2)) # N: Revealed type is "builtins.float"
[builtins fixtures/list.pyi]

[case testInferenceWithUninhabitedType]
from typing import Dict, Generic, TypeVar
from typing import Dict, Generic, List, Never, TypeVar

T = TypeVar("T")

Expand All @@ -3839,4 +3839,11 @@ def a3() -> None:
reveal_type(a) # N: Revealed type is "builtins.dict[Any, Any]"
reveal_type(b) # N: Revealed type is "builtins.dict[builtins.int, builtins.dict[Any, Any]]"
reveal_type(c) # N: Revealed type is "builtins.dict[builtins.int, builtins.dict[builtins.str, builtins.dict[Any, Any]]]"

def a4(x: List[str], y: List[Never]) -> None:
z1 = [x, y]
z2 = [y, x]
reveal_type(z1) # N: Revealed type is "builtins.list[builtins.object]"
reveal_type(z2) # N: Revealed type is "builtins.list[builtins.object]"
z1[1].append("asdf") # E: "object" has no attribute "append"
[builtins fixtures/dict.pyi]