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Fix nondeterministic type checking caused by nonassociative of None joins #19158

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Merged
merged 2 commits into from
May 28, 2025
Merged

Fix nondeterministic type checking caused by nonassociative of None joins #19158

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b35fba1
Fix nondeterministic type checking caused by nonassociative of None j…
hauntsaninja May 28, 2025
51ddef5
fix test
hauntsaninja May 28, 2025
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2 changes: 2 additions & 0 deletions mypy/solve.py
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Original file line number Diff line number Diff line change
Expand Up @@ -250,6 +250,8 @@ def solve_iteratively(
def _join_sorted_key(t: Type) -> int:
t = get_proper_type(t)
if isinstance(t, UnionType):
return -2
if isinstance(t, NoneType):
return -1
return 0

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13 changes: 13 additions & 0 deletions test-data/unit/check-generics.test
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Expand Up @@ -3602,4 +3602,17 @@ def draw(
reveal_type(c1) # N: Revealed type is "Union[builtins.int, builtins.str]"
reveal_type(c2) # N: Revealed type is "Union[builtins.int, builtins.str]"
reveal_type(c3) # N: Revealed type is "Union[builtins.int, builtins.str]"

def takes_int_str_none(x: int | str | None) -> None: ...

def draw_none(
colors1: A[str] | B[str] | C[int] | D[None],
colors2: A[str] | B[str] | C[int] | D[None],
colors3: A[str] | B[str] | C[int] | D[None],
) -> None:
for c1, c2, c3 in zip2(colors1, colors2, colors3):
# TODO: can't do reveal type because the union order is not deterministic
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I wonder if there is a way to avoid non-deterministic union order altogether, e.g. by not putting types into sets?

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Nvm, you mention this in the issue description.

takes_int_str_none(c1)
takes_int_str_none(c2)
takes_int_str_none(c3)
[builtins fixtures/tuple.pyi]
2 changes: 1 addition & 1 deletion test-data/unit/check-varargs.test
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Expand Up @@ -631,7 +631,7 @@ T = TypeVar('T')
def f(*args: T) -> T: ...
reveal_type(f(*(1, None))) # N: Revealed type is "Union[Literal[1]?, None]"
reveal_type(f(1, *(None, 1))) # N: Revealed type is "Union[Literal[1]?, None]"
reveal_type(f(1, *(1, None))) # N: Revealed type is "Union[builtins.int, None]"
reveal_type(f(1, *(1, None))) # N: Revealed type is "Union[Literal[1]?, None]"
[builtins fixtures/tuple.pyi]


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