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The test suite currently fails due to a previous merge conflict that will be resolved by #19118. The Mypy primer differences are only due to different union item orders. @ilevkivskyi: Would you like to review this simple change? It is a small extension of one of your code sections. |
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mypy/meet.py Outdated
| narrow_declared_type(x, narrowed) | ||
| for x in declared.relevant_items() | ||
| narrow_declared_type(d, n) | ||
| for d, n in product( |
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This looks like the correct way of doing that, despite higher comp complexity. What's more mypyc-friendly - itertools.product or a plain listcomp with two for clauses?
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I feel like plain listcomp would be faster (we're consuming all the items anyways), but I would be surprised if this is a hot path because there's an is_subtype check -- surely that's somewhat slow!
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Thanks for the feedback!
I have no experience with Mypyc, so I can only guess, and would agree with @A5rocks that the possible overhead of itertools.product (if it exists) should be negligible compared to the cost of the additional calls to narrow_declared_type, is_overlapping_types, and is_subtype.
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itertools.product may not be a significant bottleneck here, but I'd like to avoid it so that new code is less likely to follow the example and add usages in locations where it will be a bottleneck. Also it might slow things down measurably in very simple cases at least, e.g. union of 2 items. I'd prefer to write this using list comprehensions for these reasons.
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Okay, I removed itertools.product. The second-best readable solution that came to mind. No list comprehensions; I hope that's fine.
A5rocks approved these changes Jun 10, 2025
mypy/meet.py Outdated
| narrow_declared_type(x, narrowed) | ||
| for x in declared.relevant_items() | ||
| narrow_declared_type(d, n) | ||
| for d, n in product( |
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I feel like plain listcomp would be faster (we're consuming all the items anyways), but I would be surprised if this is a hot path because there's an is_subtype check -- surely that's somewhat slow!
Diff from mypy_primer, showing the effect of this PR on open source code: ibis (https://.com/ibis-project/ibis)
- ibis/backends/mssql/__init__.py:691: error: Item "Mapping[str, str | DataType]" of "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]" has no attribute "to_sqlglot" [union-attr]
- ibis/backends/mssql/__init__.py:691: error: Item "Iterable[tuple[str, str | DataType]]" of "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]" has no attribute "to_sqlglot" [union-attr]
- ibis/backends/mssql/__init__.py:738: error: Argument "schema" to "DatabaseTable" has incompatible type "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]"; expected "Schema" [arg-type]
+ ibis/backends/mssql/__init__.py:691: error: Item "Mapping[str, str | DataType]" of "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any" has no attribute "to_sqlglot" [union-attr]
+ ibis/backends/mssql/__init__.py:691: error: Item "Iterable[tuple[str, str | DataType]]" of "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any" has no attribute "to_sqlglot" [union-attr]
+ ibis/backends/mssql/__init__.py:738: error: Argument "schema" to "DatabaseTable" has incompatible type "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any"; expected "Schema" [arg-type]
- ibis/backends/databricks/__init__.py:215: error: Item "Mapping[str, str | DataType]" of "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | None" has no attribute "to_sqlglot" [union-attr]
- ibis/backends/databricks/__init__.py:215: error: Item "Iterable[tuple[str, str | DataType]]" of "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | None" has no attribute "to_sqlglot" [union-attr]
+ ibis/backends/databricks/__init__.py:215: error: Item "Mapping[str, str | DataType]" of "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any | None" has no attribute "to_sqlglot" [union-attr]
+ ibis/backends/databricks/__init__.py:215: error: Item "Iterable[tuple[str, str | DataType]]" of "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any | None" has no attribute "to_sqlglot" [union-attr]
- ibis/backends/databricks/__init__.py:215: error: Item "None" of "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | None" has no attribute "to_sqlglot" [union-attr]
+ ibis/backends/databricks/__init__.py:215: error: Item "None" of "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any | None" has no attribute "to_sqlglot" [union-attr]
- ibis/backends/risingwave/__init__.py:564: error: Item "Mapping[str, str | DataType]" of "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]" has no attribute "to_sqlglot" [union-attr]
- ibis/backends/risingwave/__init__.py:564: error: Item "Iterable[tuple[str, str | DataType]]" of "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]" has no attribute "to_sqlglot" [union-attr]
- ibis/backends/risingwave/__init__.py:602: error: Argument "schema" to "DatabaseTable" has incompatible type "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]"; expected "Schema" [arg-type]
+ ibis/backends/risingwave/__init__.py:564: error: Item "Mapping[str, str | DataType]" of "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any" has no attribute "to_sqlglot" [union-attr]
+ ibis/backends/risingwave/__init__.py:564: error: Item "Iterable[tuple[str, str | DataType]]" of "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any" has no attribute "to_sqlglot" [union-attr]
+ ibis/backends/risingwave/__init__.py:602: error: Argument "schema" to "DatabaseTable" has incompatible type "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any"; expected "Schema" [arg-type]
- ibis/backends/postgres/__init__.py:646: error: Item "Mapping[str, str | DataType]" of "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]" has no attribute "to_sqlglot" [union-attr]
- ibis/backends/postgres/__init__.py:646: error: Item "Iterable[tuple[str, str | DataType]]" of "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]" has no attribute "to_sqlglot" [union-attr]
- ibis/backends/postgres/__init__.py:678: error: Argument "schema" to "DatabaseTable" has incompatible type "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]"; expected "Schema" [arg-type]
+ ibis/backends/postgres/__init__.py:646: error: Item "Mapping[str, str | DataType]" of "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any" has no attribute "to_sqlglot" [union-attr]
+ ibis/backends/postgres/__init__.py:646: error: Item "Iterable[tuple[str, str | DataType]]" of "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any" has no attribute "to_sqlglot" [union-attr]
+ ibis/backends/postgres/__init__.py:678: error: Argument "schema" to "DatabaseTable" has incompatible type "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any"; expected "Schema" [arg-type]
- ibis/backends/mysql/__init__.py:411: error: Item "Mapping[str, str | DataType]" of "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]" has no attribute "to_sqlglot" [union-attr]
- ibis/backends/mysql/__init__.py:411: error: Item "Iterable[tuple[str, str | DataType]]" of "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]" has no attribute "to_sqlglot" [union-attr]
- ibis/backends/mysql/__init__.py:438: error: Argument "schema" to "DatabaseTable" has incompatible type "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]"; expected "Schema" [arg-type]
+ ibis/backends/mysql/__init__.py:411: error: Item "Mapping[str, str | DataType]" of "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any" has no attribute "to_sqlglot" [union-attr]
+ ibis/backends/mysql/__init__.py:411: error: Item "Iterable[tuple[str, str | DataType]]" of "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any" has no attribute "to_sqlglot" [union-attr]
+ ibis/backends/mysql/__init__.py:438: error: Argument "schema" to "DatabaseTable" has incompatible type "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any"; expected "Schema" [arg-type]
- ibis/backends/exasol/__init__.py:385: error: Item "Mapping[str, str | DataType]" of "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]" has no attribute "to_sqlglot" [union-attr]
- ibis/backends/exasol/__init__.py:385: error: Item "Iterable[tuple[str, str | DataType]]" of "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]" has no attribute "to_sqlglot" [union-attr]
- ibis/backends/exasol/__init__.py:410: error: Argument "schema" to "DatabaseTable" has incompatible type "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]"; expected "Schema" [arg-type]
+ ibis/backends/exasol/__init__.py:385: error: Item "Mapping[str, str | DataType]" of "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any" has no attribute "to_sqlglot" [union-attr]
+ ibis/backends/exasol/__init__.py:385: error: Item "Iterable[tuple[str, str | DataType]]" of "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any" has no attribute "to_sqlglot" [union-attr]
+ ibis/backends/exasol/__init__.py:410: error: Argument "schema" to "DatabaseTable" has incompatible type "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any"; expected "Schema" [arg-type]
- ibis/backends/duckdb/__init__.py:190: error: Item "Mapping[str, str | DataType]" of "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]" has no attribute "null_fields" [union-attr]
- ibis/backends/duckdb/__init__.py:190: error: Item "Iterable[tuple[str, str | DataType]]" of "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]" has no attribute "null_fields" [union-attr]
- ibis/backends/duckdb/__init__.py:203: error: Item "Mapping[str, str | DataType]" of "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]" has no attribute "to_sqlglot" [union-attr]
- ibis/backends/duckdb/__init__.py:203: error: Item "Iterable[tuple[str, str | DataType]]" of "Schema | Any | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]]" has no attribute "to_sqlglot" [union-attr]
+ ibis/backends/duckdb/__init__.py:190: error: Item "Mapping[str, str | DataType]" of "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any" has no attribute "null_fields" [union-attr]
+ ibis/backends/duckdb/__init__.py:190: error: Item "Iterable[tuple[str, str | DataType]]" of "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any" has no attribute "null_fields" [union-attr]
+ ibis/backends/duckdb/__init__.py:203: error: Item "Mapping[str, str | DataType]" of "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any" has no attribute "to_sqlglot" [union-attr]
+ ibis/backends/duckdb/__init__.py:203: error: Item "Iterable[tuple[str, str | DataType]]" of "Schema | Mapping[str, str | DataType] | Iterable[tuple[str, str | DataType]] | Any" has no attribute "to_sqlglot" [union-attr]
pandas (https://.com/pandas-dev/pandas)
- pandas/core/arrays/_mixins.py:150: error: Argument "dtype" to "view" of "ndarray" has incompatible type "ExtensionDtype | dtype[Any]"; expected "dtype[Any] | _HasDType[dtype[Any]]" [arg-type]
+ pandas/core/arrays/_mixins.py:150: error: Argument "dtype" to "view" of "ndarray" has incompatible type "dtype[Any] | ExtensionDtype"; expected "dtype[Any] | _HasDType[dtype[Any]]" [arg-type]
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Fixes #14987
I was puzzled as to why my previous attempts to avoid false
unreachablewarnings for loops failed for issue #14987. After some debugging, I realised that the underlying problem is that type narrowing does not work with promotions if both the declared type and the constraining type are unions:The fix seems straightforward (but let's see what the Mypy primer says) and is checked by the test cases
testNarrowPromotionsInsideUnions1andtestNarrowPromotionsInsideUnions2.