Fix handling of named tuples in class match pattern #18663
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JukkaL
approved these changes
Feb 12, 2025
| def f(t: T) -> None: | ||
| match t: | ||
| case T([K() as k]): | ||
| reveal_type(k) # N: Revealed type is "Tuple[builtins.int, fallback=__main__.K]" |
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I wonder if there is a test case like this, which would cover structural matching of named tuples:
from typing import NamedTuple
class N(NamedTuple):
x: int
y: str
a = N(1, "a")
match a:
case [x, y]:
reveal_type(x)
reveal_type(y)There was a problem hiding this comment.
No, I don't see such test, will add one.
|
According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
ilevkivskyi
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that referenced
this pull request
Feb 13, 2025
Previously a code path was introduced that made fallback a subtype of its tuple type for non-generic tuples, while the intention was to cover `tuple[Any, ...]` and similar. I add a unit test + some refactoring to make this mistake much harder in future. This may need to wait for #18663 to avoid "regressions" (the other fix needed to avoid "regressions" is already merged).
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Fixes #15299
The fix is straightforward, named tuples should be properly represented as tuples with fallback, not as instances.