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tuple slice should not propagate fallback #16154

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merged 6 commits into from
Oct 1, 2023
Merged

tuple slice should not propagate fallback #16154

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450d83d
tuple slice should not propagate fallback
graingert Sep 21, 2023
aa5889f
[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Sep 21, 2023
c1f221a
Merge branch 'master' into tuple-fallback-fix
graingert Sep 30, 2023
db88805
Update mypy/types.py
graingert Oct 1, 2023
d8aaa18
add testTupleSubclassSlice case
graingert Oct 1, 2023
f350785
Merge branch 'master' into tuple-fallback-fix
graingert Oct 1, 2023
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2 changes: 1 addition & 1 deletion mypy/checkexpr.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4271,7 +4271,7 @@ def visit_tuple_slice_helper(self, left_type: TupleType, slic: SliceExpr) -> Typ

items: list[Type] = []
for b, e, s in itertools.product(begin, end, stride):
item = left_type.slice(b, e, s)
item = left_type.slice(b, e, s, fallback=self.named_type("builtins.tuple"))
if item is None:
self.chk.fail(message_registry.AMBIGUOUS_SLICE_OF_VARIADIC_TUPLE, slic)
return AnyType(TypeOfAny.from_error)
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9 changes: 7 additions & 2 deletions mypy/types.py
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Expand Up @@ -2416,7 +2416,12 @@ def copy_modified(
items = self.items
return TupleType(items, fallback, self.line, self.column)

def slice(self, begin: int | None, end: int | None, stride: int | None) -> TupleType | None:
def slice(
self, begin: int | None, end: int | None, stride: int | None, *, fallback: Instance | None
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@graingert graingert Sep 21, 2023 •
edited

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fallback should always be named_type("builtins.tuple") but I'm not sure how to make one without access to a TypeChecker instance

) -> TupleType | None:
if fallback is None:
fallback = self.partial_fallback

if any(isinstance(t, UnpackType) for t in self.items):
total = len(self.items)
unpack_index = find_unpack_in_list(self.items)
Expand Down Expand Up @@ -2462,7 +2467,7 @@ def slice(self, begin: int | None, end: int | None, stride: int | None) -> Tuple
return None
else:
slice_items = self.items[begin:end:stride]
return TupleType(slice_items, self.partial_fallback, self.line, self.column, self.implicit)
return TupleType(slice_items, fallback, self.line, self.column, self.implicit)


class TypedDictType(ProperType):
Expand Down
9 changes: 5 additions & 4 deletions test-data/unit/check-literal.test
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Expand Up @@ -1872,8 +1872,9 @@ reveal_type(tup2[idx3]) # N: Revealed type is "__main__.D"
reveal_type(tup2[idx4]) # N: Revealed type is "__main__.E"
reveal_type(tup2[idx_neg1]) # N: Revealed type is "__main__.E"
tup2[idx5] # E: Tuple index out of range
reveal_type(tup2[idx2:idx4]) # N: Revealed type is "Tuple[__main__.C, __main__.D, fallback=__main__.Tup2Class]"
reveal_type(tup2[::idx2]) # N: Revealed type is "Tuple[__main__.A, __main__.C, __main__.E, fallback=__main__.Tup2Class]"
reveal_type(tup2[idx2:idx4]) # N: Revealed type is "Tuple[__main__.C, __main__.D]"
reveal_type(tup2[::idx2]) # N: Revealed type is "Tuple[__main__.A, __main__.C, __main__.E]"
tup3: Tup2Class = tup2[:] # E: Incompatible types in assignment (expression has type "Tuple[A, B, C, D, E]", variable has type "Tup2Class")
[builtins fixtures/slice.pyi]

[case testLiteralIntelligentIndexingTypedDict]
Expand Down Expand Up @@ -1977,8 +1978,8 @@ reveal_type(tup1[0::idx1]) # N: Revealed type is "Union[Tuple[__main__.A, _
tup1[idx_bad] # E: Tuple index out of range

reveal_type(tup2[idx1]) # N: Revealed type is "Union[__main__.B, __main__.C]"
reveal_type(tup2[idx1:idx2]) # N: Revealed type is "Union[Tuple[__main__.B, __main__.C, fallback=__main__.Tup2Class], Tuple[__main__.B, __main__.C, __main__.D, fallback=__main__.Tup2Class], Tuple[__main__.C, fallback=__main__.Tup2Class], Tuple[__main__.C, __main__.D, fallback=__main__.Tup2Class]]"
reveal_type(tup2[0::idx1]) # N: Revealed type is "Union[Tuple[__main__.A, __main__.B, __main__.C, __main__.D, __main__.E, fallback=__main__.Tup2Class], Tuple[__main__.A, __main__.C, __main__.E, fallback=__main__.Tup2Class]]"
reveal_type(tup2[idx1:idx2]) # N: Revealed type is "Union[Tuple[__main__.B, __main__.C], Tuple[__main__.B, __main__.C, __main__.D], Tuple[__main__.C], Tuple[__main__.C, __main__.D]]"
reveal_type(tup2[0::idx1]) # N: Revealed type is "Union[Tuple[__main__.A, __main__.B, __main__.C, __main__.D, __main__.E], Tuple[__main__.A, __main__.C, __main__.E]]"
tup2[idx_bad] # E: Tuple index out of range
[builtins fixtures/slice.pyi]
[out]
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10 changes: 10 additions & 0 deletions test-data/unit/check-tuples.test
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Expand Up @@ -1681,3 +1681,13 @@ def g(t: Tuple):
reveal_type(zip(*t)) # N: Revealed type is "typing.Iterator[builtins.tuple[Any, ...]]"
reveal_type(zip(t)) # N: Revealed type is "typing.Iterator[Tuple[Any]]"
[builtins fixtures/tuple.pyi]

[case testTupleSubclassSlice]
from typing import Tuple

class A: ...

class tuple_aa_subclass(Tuple[A, A]): ...

inst_tuple_aa_subclass: tuple_aa_subclass = tuple_aa_subclass((A(), A()))[:] # E: Incompatible types in assignment (expression has type "Tuple[A, A]", variable has type "tuple_aa_subclass")
[builtins fixtures/tuple.pyi]