8000 Fix simplification of some unions · python/mypy@f43fd8f · GitHub
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JukkaLJukkaL
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Fix simplification of some unions
In particular, this helps with classes that have Any base classes. This is enough to fix #2712. This is almost a subset of #2714 and should land before that, as this should cause less disruption.
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+74
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lines changed

3 files changed

+74
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‎mypy/types.py

Lines changed: 6 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1034,13 +1034,18 @@ def make_simplified_union(items: List[Type], line: int = -1, column: int = -1) -
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return AnyType()
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from mypy.subtypes import is_subtype
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from mypy.sametypes import is_same_type
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removed = set() # type: Set[int]
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for i, ti in enumerate(items):
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if i in removed: continue
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# Keep track of the truishness info for deleted subtypes which can be relevant
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cbt = cbf = False
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for j, tj in enumerate(items):
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if i != j and is_subtype(tj, ti):
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if (i != j
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and is_subtype(tj, ti)
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and (not (isinstance(tj, Instance) and tj.type.fallback_to_any)
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or is_same_type(ti, tj))):
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removed.add(j)
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cbt = cbt or tj.can_be_true
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cbf = cbf or tj.can_be_false

‎test-data/unit/check-optional.test

Lines changed: 19 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -525,3 +525,22 @@ f = None # type: Optional[Callable[[int], None]]
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f = lambda x: None
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f(0)
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[builtins fixtures/function.pyi]
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[case testUnionSimplificationWithStrictOptional]
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from typing import Any, TypeVar, Union
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class C(Any): pass
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T = TypeVar('T')
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S = TypeVar('S')
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def u(x: T, y: S) -> Union[S, T]: pass
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a = None # type: Any
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# Test both orders
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reveal_type(u(C(), None)) # E: Revealed type is 'Union[builtins.None, __main__.C*]'
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reveal_type(u(None, C())) # E: Revealed type is 'Union[__main__.C*, builtins.None]'
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# This will be fixed later
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reveal_type(u(a, None)) # E: Revealed type is 'Any'
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reveal_type(u(None, a)) # E: Revealed type is 'Any'
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reveal_type(u(1, None)) # E: Revealed type is 'Union[builtins.None, builtins.int*]'
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reveal_type(u(None, 1)) # E: Revealed type is 'Union[builtins.int*, builtins.None]'

‎test-data/unit/check-unions.test

Lines changed: 49 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -168,3 +168,52 @@ if foo():
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def g(x: Union[int, str, bytes]) -> None: pass
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else:
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def g(x: Union[int, str]) -> None: pass # E: All conditional function variants must have identical signatures
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[case testUnionSimplificationSpecialCases]
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from typing import Any, TypeVar, Union
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class C(Any): pass
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T = TypeVar('T')
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S = TypeVar('S')
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def u(x: T, y: S) -> Union[S, T]: pass
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a = None # type: Any
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reveal_type(u(C(), None)) # E: Revealed type is '__main__.C*'
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reveal_type(u(None, C())) # E: Revealed type is '__main__.C*'
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# This will be fixed later
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reveal_type(u(C(), a)) # E: Revealed type is 'Any'
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reveal_type(u(a, C())) # E: Revealed type is 'Any'
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reveal_type(u(C(), C())) # E: Revealed type is '__main__.C*'
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reveal_type(u(a, a)) # E: Revealed type is 'Any'
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[case testUnionSimplificationSpecialCase2]
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from typing import Any, TypeVar, Union
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class C(Any): pass
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T = TypeVar('T')
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S = TypeVar('S')
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def u(x: T, y: S) -> Union[S, T]: pass
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def f(x: T) -> None:
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reveal_type(u(C(), x)) # E: Revealed type is 'Union[T`-1, __main__.C*]'
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reveal_type(u(x, C())) # E: Revealed type is 'Union[__main__.C*, T`-1]'
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[case testUnionSimplificationSpecialCase3]
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from typing import Any, TypeVar, Generic, Union
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class C(Any): pass
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V = TypeVar('V')
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T = TypeVar('T')
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class M(Generic[V]):
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def get(self, default: T) -> Union[V, T]: ...
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def f(x: M[C]) -> None:
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y = x.get(None)
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reveal_type(y) # E: Revealed type is '__main__.C'

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