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Fix match statement issue#11363

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gramster wants to merge 2 commits intomicrosoft:mainfrom
gramster:fix-match-statement-issue
Open

Fix match statement issue#11363
gramster wants to merge 2 commits intomicrosoft:mainfrom
gramster:fix-match-statement-issue

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@gramster gramster commented Apr 7, 2026

Fix pattern matching regression for variadic tuple types
When a tuple with an unbounded entry (e.g., tuple[int, *tuple[str, ...], int])
is matched against a pattern shorter than the tuple, the unbounded entry is
removed to make lengths match. However, this loses the information that the
tuple was originally variadic and could have different lengths.

The fix tracks when an unbounded entry is removed (removedIndeterminate flag)
and marks such matches as isPotentialNoMatch=true. This prevents the entire
variadic tuple from being eliminated in negative narrowing, preserving
reachability of subsequent match cases.

Fixes #10845

Copilot AI and others added 2 commits April 6, 2026 17:30
When a tuple with an unbounded entry (e.g., tuple[int, *tuple[str, ...], int])
is matched against a pattern shorter than the tuple, the unbounded entry is
removed to make lengths match. However, this loses the information that the
tuple was originally variadic and could have different lengths.

The fix tracks when an unbounded entry is removed (removedIndeterminate flag)
and marks such matches as isPotentialNoMatch=true. This prevents the entire
variadic tuple from being eliminated in negative narrowing, preserving
reachability of subsequent match cases.
@gramster gramster requested review from heejaechang and rchiodo April 7, 2026 00:36
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github-actions bot commented Apr 7, 2026

Diff from mypy_primer, showing the effect of this PR on open source code:

sympy (https://github.com/sympy/sympy)
+   .../projects/sympy/sympy/solvers/tests/test_solveset.py:445:30 - error: Cannot access attribute "limit_denominator" for class "NaN"
+     Attribute "limit_denominator" is unknown (reportAttributeAccessIssue)
+   .../projects/sympy/sympy/solvers/tests/test_solveset.py:445:30 - error: Cannot access attribute "limit_denominator" for class "ComplexInfinity"
+     Attribute "limit_denominator" is unknown (reportAttributeAccessIssue)
-   .../projects/sympy/sympy/solvers/tests/test_solveset.py:620:16 - error: No overloads for "__new__" match the provided arguments (reportCallIssue)
-   .../projects/sympy/sympy/solvers/tests/test_solveset.py:620:19 - error: Argument of type "Expr | Unknown | float" cannot be assigned to parameter "arg" of type "Expr" in function "__new__"
-     Type "Expr | Unknown | float" is not assignable to type "Expr"
-       "float" is not assignable to "Expr" (reportArgumentType)
-   .../projects/sympy/sympy/solvers/tests/test_solveset.py:625:16 - error: No overloads for "__new__" match the provided arguments (reportCallIssue)
-   .../projects/sympy/sympy/solvers/tests/test_solveset.py:625:19 - error: Argument of type "Expr | Unknown | float" cannot be assigned to parameter "arg" of type "Expr" in function "__new__"
-     Type "Expr | Unknown | float" is not assignable to type "Expr"
-       "float" is not assignable to "Expr" (reportArgumentType)
+   .../projects/sympy/sympy/stats/crv_types.py:2543:9 - error: Method "_cdf" overrides class "SingleContinuousDistribution" in an incompatible manner
+     Return type mismatch: base method returns type "None", override returns type "ComplexInfinity | NaN | Rational | Unknown"
+       Type "ComplexInfinity | NaN | Rational | Unknown" is not assignable to type "None"
+         "ComplexInfinity" is not assignable to "None" (reportIncompatibleMethodOverride)
+   .../projects/sympy/sympy/stats/crv_types.py:2722:9 - error: Method "_cdf" overrides class "SingleContinuousDistribution" in an incompatible manner
+     Return type mismatch: base method returns type "None", override returns type "Expr | NaN | ComplexInfinity | Rational | Unknown"
+       Type "Expr | NaN | ComplexInfinity | Rational | Unknown" is not assignable to type "None"
+         "Expr" is not assignable to "None" (reportIncompatibleMethodOverride)
+   .../projects/sympy/sympy/stats/frv_types.py:139:17 - error: Argument of type "NaN | ComplexInfinity | Rational | Unknown | Expr" cannot be assigned to parameter "value" of type "int" in function "__setitem__"
+     Type "NaN | ComplexInfinity | Rational | Unknown | Expr" is not assignable to type "int"
+       "Expr" is not assignable to "int" (reportArgumentType)
-   .../projects/sympy/sympy/stats/joint_rv_types.py:576:27 - error: Argument of type "One | NegativeOne | Zero | Integer | NaN | ComplexInfinity | Rational | Unknown | Infinity | NegativeInfinity | Float | Number | Expr" cannot be assigned to parameter "stop" of type "SupportsIndex" in function "__new__"
+   .../projects/sympy/sympy/stats/joint_rv_types.py:576:27 - error: Argument of type "One | NegativeOne | Zero | Integer | NaN | ComplexInfinity | Rational | Infinity | NegativeInfinity | Float | Number | Expr" cannot be assigned to parameter "stop" of type "SupportsIndex" in function "__new__"
-     Type "One | NegativeOne | Zero | Integer | NaN | ComplexInfinity | Rational | Unknown | Infinity | NegativeInfinity | Float | Number | Expr" is not assignable to type "SupportsIndex"
+     Type "One | NegativeOne | Zero | Integer | NaN | ComplexInfinity | Rational | Infinity | NegativeInfinity | Float | Number | Expr" is not assignable to type "SupportsIndex"
-   .../projects/sympy/sympy/stats/rv_interface.py:451:42 - error: Operator "-" not supported for types "Unknown | Basic | Any" and "Rational | Unknown"
+   .../projects/sympy/sympy/stats/rv_interface.py:451:42 - error: Operator "-" not supported for types "Unknown | Basic | Any" and "Rational | NaN | ComplexInfinity"
+     Operator "-" not supported for types "Basic" and "Rational"
+     Operator "-" not supported for types "Basic" and "NaN"
-     Operator "-" not supported for types "Basic" and "Rational" (reportOperatorIssue)
+     Operator "-" not supported for types "Basic" and "ComplexInfinity" (reportOperatorIssue)
-   .../projects/sympy/sympy/stats/tests/test_finite_rv.py:35:23 - error: Operator "/" not supported for types "Unknown | Any | One | NegativeOne | Zero | Integer | NaN | ComplexInfinity | Rational | Expr | MatMul | Infinity | NegativeInfinity | Float | NotImplementedType | tuple[Unknown, ...] | int" and "Unknown | Any | BernoulliDistribution | Probability | Zero | One | tuple[Unknown, ...] | Sum | Expr | ZeroMatrix | NaN | Piecewise | Basic | ComplexInfinity | Float | Infinity | Integer | Lambda | Mul | NegativeInfinity | NegativeOne | Number | Rational | Integral | Literal[0]"
+   .../projects/sympy/sympy/stats/tests/test_finite_rv.py:35:23 - error: Operator "/" not supported for types "Unknown | Any | One | NegativeOne | Zero | Integer | NaN | ComplexInfinity | Rational | Expr | MatMul | tuple[Unknown, ...] | Infinity | NegativeInfinity | int" and "Unknown | Any | BernoulliDistribution | Probability | Zero | One | tuple[Unknown, ...] | Sum | Expr | ZeroMatrix | NaN | Piecewise | Basic | ComplexInfinity | Float | Infinity | Integer | Lambda | Mul | NegativeInfinity | NegativeOne | Number | Rational | Integral | Literal[0]"
-   .../projects/sympy/sympy/stats/tests/test_finite_rv.py:247:19 - error: Argument of type "Rational | Unknown" cannot be assigned to parameter "p" of type "Half" in function "Coin"
+   .../projects/sympy/sympy/stats/tests/test_finite_rv.py:247:19 - error: Argument of type "Rational | NaN | ComplexInfinity" cannot be assigned to parameter "p" of type "Half" in function "Coin"
-     Type "Rational | Unknown" is not assignable to type "Half"
+     Type "Rational | NaN | ComplexInfinity" is not assignable to type "Half"
-       "Rational" is not assignable to "Half" (reportArgumentType)
+       "ComplexInfinity" is not assignable to "Half" (reportArgumentType)
-   .../projects/sympy/sympy/tensor/array/expressions/from_array_to_matrix.py:402:32 - error: Cannot access attribute "shape" for class "Infinity"
-     Attribute "shape" is unknown (reportAttributeAccessIssue)
-   .../projects/sympy/sympy/tensor/array/expressions/from_array_to_matrix.py:402:32 - error: Cannot access attribute "shape" for class "NegativeInfinity"
-     Attribute "shape" is unknown (reportAttributeAccessIssue)
-   .../projects/sympy/sympy/tensor/array/expressions/from_array_to_matrix.py:402:32 - error: Cannot access attribute "shape" for class "Float"
-     Attribute "shape" is unknown (reportAttributeAccessIssue)
-   .../projects/sympy/sympy/tensor/array/expressions/from_array_to_matrix.py:428:25 - error: Cannot access attribute "shape" for class "Infinity"
-     Attribute "shape" is unknown (reportAttributeAccessIssue)
-   .../projects/sympy/sympy/tensor/array/expressions/from_array_to_matrix.py:428:25 - error: Cannot access attribute "shape" for class "NegativeInfinity"
-     Attribute "shape" is unknown (reportAttributeAccessIssue)
-   .../projects/sympy/sympy/tensor/array/expressions/from_array_to_matrix.py:428:25 - error: Cannot access attribute "shape" for class "Float"
-     Attribute "shape" is unknown (reportAttributeAccessIssue)
-   .../projects/sympy/sympy/tensor/array/expressions/from_array_to_matrix.py:438:31 - error: Operator "*" not supported for types "Zero | ZeroArray | Unknown | ArrayContraction | Basic | PermuteDims | Any | Transpose | One | NegativeOne | Integer | NaN | ComplexInfinity | Rational | Infinity | NegativeInfinity | Float | NotImplementedType | Expr | MatMul" and "Zero | ZeroArray | Unknown | ArrayContraction | Basic | PermuteDims | Any | Transpose | MatrixExpr"
+   .../projects/sympy/sympy/tensor/array/expressions/from_array_to_matrix.py:438:31 - error: Operator "*" not supported for types "Zero | ZeroArray | Unknown | ArrayContraction | Basic | PermuteDims | Any | Transpose | One | NegativeOne | Integer | NaN | ComplexInfinity | Rational | Expr | MatMul" and "Zero | ZeroArray | Unknown | ArrayContraction | Basic | PermuteDims | Any | Transpose | MatrixExpr"
+   .../projects/sympy/sympy/tensor/tensor.py:4366:42 - error: Operator "*" not supported for types "One | NegativeOne | Zero | Integer | NaN | ComplexInfinity | Rational | Unknown" and "Basic | Unknown"
+     Operator "*" not supported for types "ComplexInfinity" and "Basic" when expected type is "One | NegativeOne | Zero | Integer | NaN | ComplexInfinity | Rational | Unknown" (reportOperatorIssue)
-   .../projects/sympy/sympy/tensor/tests/test_functions.py:41:17 - error: Cannot access attribute "shape" for class "Infinity"
-     Attribute "shape" is unknown (reportAttributeAccessIssue)
-   .../projects/sympy/sympy/tensor/tests/test_functions.py:41:17 - error: Cannot access attribute "shape" for class "NegativeInfinity"
-     Attribute "shape" is unknown (reportAttributeAccessIssue)
-   .../projects/sympy/sympy/tensor/tests/test_functions.py:41:17 - error: Cannot access attribute "shape" for class "Float"
-     Attribute "shape" is unknown (reportAttributeAccessIssue)
-   .../projects/sympy/sympy/tensor/tests/test_functions.py:41:17 - error: Cannot access attribute "shape" for class "Expr"
-     Attribute "shape" is unknown (reportAttributeAccessIssue)
-     Attribute "rank" is unknown (reportAttributeAccessIssue)
-   .../projects/sympy/sympy/tensor/tests/test_functions.py:42:17 - error: Cannot access attribute "rank" for class "Infinity"
-     Attribute "rank" is unknown (reportAttributeAccessIssue)
-   .../projects/sympy/sympy/tensor/tests/test_functions.py:42:17 - error: Cannot access attribute "rank" for class "NegativeInfinity"
-     Attribute "rank" is unknown (reportAttributeAccessIssue)

... (truncated 540 lines) ...

jax (https://github.com/google/jax)
+   .../projects/jax/jax/_src/pallas/mosaic/sc_lowering.py:785:11 - error: "log_buffer" is not a known attribute of module "jaxlib.mosaic.python.tpu" (reportAttributeAccessIssue)
+   .../projects/jax/jax/_src/pallas/mosaic/sc_lowering.py:787:11 - error: "log" is not a known attribute of module "jaxlib.mosaic.python.tpu" (reportAttributeAccessIssue)
- 3083 errors, 83 warnings, 0 informations
+ 3085 errors, 83 warnings, 0 informations

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Methods of a variadic generic class become uncallable when specified with TypeVarTuple and a suffix

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