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specify that parameter specification should have variance
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‎conformance/results/mypy/generics_paramspec_variance.toml‎

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conformant = "Unsupported"
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conformance_automated = "Fail"
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errors_diff = """
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Line 24: Expected 1 errors
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Line 31: Expected 1 errors
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Line 47: Expected 1 errors
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Line 23: Unexpected errors ['generics_paramspec_variance.py:23: error: Incompatible types in assignment (expression has type "CovariantParamSpec[[int]]", variable has type "CovariantParamSpec[[object]]") [assignment]']
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Line 26: Unexpected errors ['generics_paramspec_variance.py:26: error: The variance and bound arguments to ParamSpec do not have defined semantics yet [misc]']
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Line 30: Unexpected errors ['generics_paramspec_variance.py:30: error: Missing return statement [empty-body]']
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Line 37: Unexpected errors ['generics_paramspec_variance.py:37: error: The variance and bound arguments to ParamSpec do not have defined semantics yet [misc]']
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Line 46: Unexpected errors ['generics_paramspec_variance.py:46: error: Incompatible types in assignment (expression has type "CovariantParamSpecOld[[int]]", variable has type "CovariantParamSpecOld[[object]]") [assignment]']
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"""
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output = """
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generics_paramspec_variance.py:15: error: Incompatible types in assignment (expression has type "ContravariantParamSpec[[int]]", variable has type "ContravariantParamSpec[[object]]") [assignment]
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generics_paramspec_variance.py:23: error: Incompatible types in assignment (expression has type "CovariantParamSpec[[int]]", variable has type "CovariantParamSpec[[object]]") [assignment]
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generics_paramspec_variance.py:26: error: The variance and bound arguments to ParamSpec do not have defined semantics yet [misc]
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generics_paramspec_variance.py:30: error: Missing return statement [empty-body]
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generics_paramspec_variance.py:35: error: Incompatible types in assignment (expression has type "ContravariantParamSpecOld[[int]]", variable has type "ContravariantParamSpecOld[[object]]") [assignment]
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generics_paramspec_variance.py:37: error: The variance and bound arguments to ParamSpec do not have defined semantics yet [misc]
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generics_paramspec_variance.py:41: error: Missing return statement [empty-body]
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generics_paramspec_variance.py:46: error: Incompatible types in assignment (expression has type "CovariantParamSpecOld[[int]]", variable has type "CovariantParamSpecOld[[object]]") [assignment]
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"""

‎conformance/results/pyrefly/generics_paramspec_variance.toml‎

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conformant = "Unsupported"
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conformance_automated = "Fail"
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errors_diff = """
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Line 15: Expected 1 errors
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Line 24: Expected 1 errors
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Line 31: Expected 1 errors
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Line 41: Expected 1 errors
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Line 14: Unexpected errors ['`ContravariantParamSpec[[object]]` is not assignable to `ContravariantParamSpec[[int]]` [bad-assignment]']
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Line 23: Unexpected errors ['`CovariantParamSpec[[int]]` is not assignable to `CovariantParamSpec[[object]]` [bad-assignment]']
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Line 26: Unexpected errors ['Unexpected keyword argument `contravariant` to ParamSpec [invalid-param-spec]']
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Line 34: Unexpected errors ['`ContravariantParamSpecOld[[object]]` is not assignable to `ContravariantParamSpecOld[[int]]` [bad-assignment]']
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Line 37: Unexpected errors ['Unexpected keyword argument `covariant` to ParamSpec [invalid-param-spec]']
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Line 46: Unexpected errors ['`CovariantParamSpecOld[[int]]` is not assignable to `CovariantParamSpecOld[[object]]` [bad-assignment]']
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"""
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output = """
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ERROR generics_paramspec_variance.py:14:39-45: `ContravariantParamSpec[[object]]` is not assignable to `ContravariantParamSpec[[int]]` [bad-assignment]
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ERROR generics_paramspec_variance.py:23:39-46: `CovariantParamSpec[[int]]` is not assignable to `CovariantParamSpec[[object]]` [bad-assignment]
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ERROR generics_paramspec_variance.py:26:24-42: Unexpected keyword argument `contravariant` to ParamSpec [invalid-param-spec]
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ERROR generics_paramspec_variance.py:34:46-56: `ContravariantParamSpecOld[[object]]` is not assignable to `ContravariantParamSpecOld[[int]]` [bad-assignment]
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ERROR generics_paramspec_variance.py:35:14-24: `ContravariantParamSpecOld[[int]]` is not assignable to variable `in_obj_old` with type `ContravariantParamSpecOld[[object]]` [bad-assignment]
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ERROR generics_paramspec_variance.py:37:26-40: Unexpected keyword argument `covariant` to ParamSpec [invalid-param-spec]
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ERROR generics_paramspec_variance.py:46:46-57: `CovariantParamSpecOld[[int]]` is not assignable to `CovariantParamSpecOld[[object]]` [bad-assignment]
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ERROR generics_paramspec_variance.py:47:15-26: `CovariantParamSpecOld[[object]]` is not assignable to variable `out_int_old` with type `CovariantParamSpecOld[[int]]` [bad-assignment]
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"""

‎conformance/results/pyright/generics_paramspec_variance.toml‎

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conformant = "Unsupported"
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conformance_automated = "Fail"
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errors_diff = """
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Line 31: Expected 1 errors
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Line 41: Expected 1 errors
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Line 14: Unexpected errors ['generics_paramspec_variance.py:14:39 - error: Type "ContravariantParamSpec[(object)]" is not assignable to declared type "ContravariantParamSpec[(int)]"']
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Line 23: Unexpected errors ['generics_paramspec_variance.py:23:39 - error: Type "CovariantParamSpec[(int)]" is not assignable to declared type "CovariantParamSpec[(object)]"']
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Line 26: Unexpected errors ['generics_paramspec_variance.py:26:24 - error: "contravariant" is unknown parameter to ParamSpec (reportGeneralTypeIssues)']
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Line 34: Unexpected errors ['generics_paramspec_variance.py:34:46 - error: Type "ContravariantParamSpecOld[(object)]" is not assignable to declared type "ContravariantParamSpecOld[(int)]"']
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Line 37: Unexpected errors ['generics_paramspec_variance.py:37:26 - error: "covariant" is unknown parameter to ParamSpec (reportGeneralTypeIssues)']
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Line 46: Unexpected errors ['generics_paramspec_variance.py:46:46 - error: Type "CovariantParamSpecOld[(int)]" is not assignable to declared type "CovariantParamSpecOld[(object)]"']
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"""
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output = """
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generics_paramspec_variance.py:14:39 - error: Type "ContravariantParamSpec[(object)]" is not assignable to declared type "ContravariantParamSpec[(int)]"
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  "ContravariantParamSpec[(object)]" is not assignable to "ContravariantParamSpec[(int)]"
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    Type parameter "InP@ContravariantParamSpec" is invariant, but "(object)" is not the same as "(int)" (reportAssignmentType)
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generics_paramspec_variance.py:15:10 - error: Type "ContravariantParamSpec[(int)]" is not assignable to declared type "ContravariantParamSpec[(object)]"
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  "ContravariantParamSpec[(int)]" is not assignable to "ContravariantParamSpec[(object)]"
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    Type parameter "InP@ContravariantParamSpec" is invariant, but "(int)" is not the same as "(object)" (reportAssignmentType)
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generics_paramspec_variance.py:23:39 - error: Type "CovariantParamSpec[(int)]" is not assignable to declared type "CovariantParamSpec[(object)]"
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  "CovariantParamSpec[(int)]" is not assignable to "CovariantParamSpec[(object)]"
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    Type parameter "OutP@CovariantParamSpec" is invariant, but "(int)" is not the same as "(object)" (reportAssignmentType)
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generics_paramspec_variance.py:24:11 - error: Type "CovariantParamSpec[(object)]" is not assignable to declared type "CovariantParamSpec[(int)]"
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  "CovariantParamSpec[(object)]" is not assignable to "CovariantParamSpec[(int)]"
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    Type parameter "OutP@CovariantParamSpec" is invariant, but "(object)" is not the same as "(int)" (reportAssignmentType)
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generics_paramspec_variance.py:26:24 - error: "contravariant" is unknown parameter to ParamSpec (reportGeneralTypeIssues)
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generics_paramspec_variance.py:34:46 - error: Type "ContravariantParamSpecOld[(object)]" is not assignable to declared type "ContravariantParamSpecOld[(int)]"
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  "ContravariantParamSpecOld[(object)]" is not assignable to "ContravariantParamSpecOld[(int)]"
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    Type parameter "InP@ContravariantParamSpecOld" is invariant, but "(object)" is not the same as "(int)" (reportAssignmentType)
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generics_paramspec_variance.py:35:14 - error: Type "ContravariantParamSpecOld[(int)]" is not assignable to declared type "ContravariantParamSpecOld[(object)]"
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  "ContravariantParamSpecOld[(int)]" is not assignable to "ContravariantParamSpecOld[(object)]"
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    Type parameter "InP@ContravariantParamSpecOld" is invariant, but "(int)" is not the same as "(object)" (reportAssignmentType)
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generics_paramspec_variance.py:37:26 - error: "covariant" is unknown parameter to ParamSpec (reportGeneralTypeIssues)
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generics_paramspec_variance.py:46:46 - error: Type "CovariantParamSpecOld[(int)]" is not assignable to declared type "CovariantParamSpecOld[(object)]"
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  "CovariantParamSpecOld[(int)]" is not assignable to "CovariantParamSpecOld[(object)]"
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    Type parameter "OutP@CovariantParamSpecOld" is invariant, but "(int)" is not the same as "(object)" (reportAssignmentType)
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generics_paramspec_variance.py:47:15 - error: Type "CovariantParamSpecOld[(object)]" is not assignable to declared type "CovariantParamSpecOld[(int)]"
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  "CovariantParamSpecOld[(object)]" is not assignable to "CovariantParamSpecOld[(int)]"
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    Type parameter "OutP@CovariantParamSpecOld" is invariant, but "(object)" is not the same as "(int)" (reportAssignmentType)
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"""

‎conformance/results/results.html‎

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@@ -335,6 +335,13 @@ <h3>Python Type System Conformance Test Results</h3>
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<th class="column col2 conformant">Pass</th>
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<th class="column col2 conformant">Pass</th>
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</tr>
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<tr><th class="column col1">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;generics_paramspec_variance</th>
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<th class="column col2 not-conformant">Unsupported</th>
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<th class="column col2 not-conformant">Unsupported</th>
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<th class="column col2 not-conformant">Unsupported</th>
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<th class="column col2 not-conformant">Unsupported</th>
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<th class="column col2 not-conformant">Unsupported</th>
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</tr>
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<tr><th class="column col1">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;generics_scoping</th>
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<th class="column col2 conformant">Pass</th>
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<th class="column col2 conformant">Pass</th>

‎conformance/results/ty/generics_paramspec_variance.toml‎

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conformant = "Unsupported"
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conformance_automated = "Fail"
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errors_diff = """
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Line 15: Expected 1 errors
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Line 24: Expected 1 errors
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Line 35: Expected 1 errors
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Line 47: Expected 1 errors
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Line 26: Unexpected errors ['generics_paramspec_variance.py:26:7: error[invalid-paramspec] The variance and bound arguments for `ParamSpec` do not have defined semantics yet']
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Line 29: Unexpected errors ['generics_paramspec_variance.py:29:33: error[invalid-argument-type] `ParamSpec` is not a valid argument to `Generic`']
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Line 30: Unexpected errors ['generics_paramspec_variance.py:30:23: error[empty-body] Function always implicitly returns `None`, which is not assignable to return type `(...) -> Unknown`', 'generics_paramspec_variance.py:30:32: error[invalid-type-form] Variable of type `ParamSpec` is not allowed in a return type annotation', 'generics_paramspec_variance.py:30:32: error[invalid-type-form] The first argument to `Callable` must be either a list of types, ParamSpec, Concatenate, or `...`']
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Line 37: Unexpected errors ['generics_paramspec_variance.py:37:8: error[invalid-paramspec] The variance and bound arguments for `ParamSpec` do not have defined semantics yet']
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Line 40: Unexpected errors ['generics_paramspec_variance.py:40:29: error[invalid-argument-type] `ParamSpec` is not a valid argument to `Generic`']
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Line 42: Unexpected errors ['generics_paramspec_variance.py:42:34: error[invalid-type-form] Variable of type `ParamSpec` is not allowed in a parameter annotation', 'generics_paramspec_variance.py:42:34: error[invalid-type-form] The first argument to `Callable` must be either a list of types, ParamSpec, Concatenate, or `...`']
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"""
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output = """
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generics_paramspec_variance.py:26:7: error[invalid-paramspec] The variance and bound arguments for `ParamSpec` do not have defined semantics yet
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generics_paramspec_variance.py:29:33: error[invalid-argument-type] `ParamSpec` is not a valid argument to `Generic`
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generics_paramspec_variance.py:30:23: error[empty-body] Function always implicitly returns `None`, which is not assignable to return type `(...) -> Unknown`
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generics_paramspec_variance.py:30:32: error[invalid-type-form] Variable of type `ParamSpec` is not allowed in a return type annotation
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generics_paramspec_variance.py:30:32: error[invalid-type-form] The first argument to `Callable` must be either a list of types, ParamSpec, Concatenate, or `...`
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generics_paramspec_variance.py:31:34: error[invalid-type-form] Variable of type `ParamSpec` is not allowed in a parameter annotation
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generics_paramspec_variance.py:31:34: error[invalid-type-form] The first argument to `Callable` must be either a list of types, ParamSpec, Concatenate, or `...`
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generics_paramspec_variance.py:37:8: error[invalid-paramspec] The variance and bound arguments for `ParamSpec` do not have defined semantics yet
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generics_paramspec_variance.py:40:29: error[invalid-argument-type] `ParamSpec` is not a valid argument to `Generic`
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generics_paramspec_variance.py:41:23: error[empty-body] Function always implicitly returns `None`, which is not assignable to return type `(...) -> Unknown`
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generics_paramspec_variance.py:41:32: error[invalid-type-form] Variable of type `ParamSpec` is not allowed in a return type annotation
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generics_paramspec_variance.py:41:32: error[invalid-type-form] The first argument to `Callable` must be either a list of types, ParamSpec, Concatenate, or `...`
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generics_paramspec_variance.py:42:34: error[invalid-type-form] Variable of type `ParamSpec` is not allowed in a parameter annotation
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generics_paramspec_variance.py:42:34: error[invalid-type-form] The first argument to `Callable` must be either a list of types, ParamSpec, Concatenate, or `...`
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"""

‎conformance/results/zuban/generics_paramspec_variance.toml‎

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conformant = "Unsupported"
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conformance_automated = "Fail"
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errors_diff = """
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Line 24: Expected 1 errors
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Line 31: Expected 1 errors
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Line 47: Expected 1 errors
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Line 23: Unexpected errors ['generics_paramspec_variance.py:23: error: Incompatible types in assignment (expression has type "CovariantParamSpec[[int]]", variable has type "CovariantParamSpec[[object]]") [assignment]']
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Line 26: Unexpected errors ['generics_paramspec_variance.py:26: error: The variance and bound arguments to ParamSpec do not have defined semantics yet [misc]']
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Line 30: Unexpected errors ['generics_paramspec_variance.py:30: error: Missing return statement [empty-body]']
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Line 37: Unexpected errors ['generics_paramspec_variance.py:37: error: The variance and bound arguments to ParamSpec do not have defined semantics yet [misc]']
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Line 46: Unexpected errors ['generics_paramspec_variance.py:46: error: Incompatible types in assignment (expression has type "CovariantParamSpecOld[[int]]", variable has type "CovariantParamSpecOld[[object]]") [assignment]']
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"""
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output = """
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generics_paramspec_variance.py:15: error: Incompatible types in assignment (expression has type "ContravariantParamSpec[[int]]", variable has type "ContravariantParamSpec[[object]]") [assignment]
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generics_paramspec_variance.py:23: error: Incompatible types in assignment (expression has type "CovariantParamSpec[[int]]", variable has type "CovariantParamSpec[[object]]") [assignment]
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generics_paramspec_variance.py:26: error: The variance and bound arguments to ParamSpec do not have defined semantics yet [misc]
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generics_paramspec_variance.py:30: error: Missing return statement [empty-body]
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generics_paramspec_variance.py:35: error: Incompatible types in assignment (expression has type "ContravariantParamSpecOld[[int]]", variable has type "ContravariantParamSpecOld[[object]]") [assignment]
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generics_paramspec_variance.py:37: error: The variance and bound arguments to ParamSpec do not have defined semantics yet [misc]
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generics_paramspec_variance.py:41: error: Missing return statement [empty-body]
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generics_paramspec_variance.py:46: error: Incompatible types in assignment (expression has type "CovariantParamSpecOld[[int]]", variable has type "CovariantParamSpecOld[[object]]") [assignment]
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"""

‎conformance/tests/generics_paramspec_variance.py‎

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"""
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Tests variance of ParamSpec.
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"""
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# Specification: https://typing.readthedocs.io/en/latest/spec/generics.html#semantics
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from typing import Callable, Generic, ParamSpec
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class ContravariantParamSpec[**InP]:
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def f(self, *args: InP.args, **kwargs: InP.kwargs): ...
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in_obj: ContravariantParamSpec[object] = ContravariantParamSpec()
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in_int: ContravariantParamSpec[int] = in_obj # OK
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in_obj = in_int # E
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class CovariantParamSpec[**OutP]:
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def f(self, fn: Callable[OutP, None]) -> None: ...
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out_int: CovariantParamSpec[int] = CovariantParamSpec()
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out_obj: CovariantParamSpec[object] = out_int # OK
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out_int = out_obj # E
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InP = ParamSpec("InP", contravariant=True)
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class ContravariantParamSpecOld(Generic[InP]):
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def in_f(self) -> Callable[InP, None]: ... # OK
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def out_f(self, fn: Callable[InP, None]) -> None: ... # E
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in_obj_old: ContravariantParamSpecOld[object] = ContravariantParamSpecOld()
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in_int_old: ContravariantParamSpecOld[int] = in_obj_old # OK
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in_obj_old = in_int_old # E
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OutP = ParamSpec("OutP", covariant=True)
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class CovariantParamSpecOld(Generic[OutP]):
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def in_f(self) -> Callable[OutP, None]: ... # E
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def out_f(self, fn: Callable[OutP, None]) -> None: ... # OK
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out_int_old: CovariantParamSpecOld[int] = CovariantParamSpecOld()
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out_obj_old: CovariantParamSpecOld[object] = out_int_old # OK
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out_int_old = out_obj_old # E

‎docs/spec/generics.rst‎

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@@ -2712,13 +2712,12 @@ The algorithm for computing the variance of a type parameter is as follows.
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For each type parameter in a generic class:
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1. If the type parameter is variadic (``TypeVarTuple``) or a parameter
2716-
specification (``ParamSpec``), it is always considered invariant. No further
2717-
inference is needed.
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1. If the type parameter is variadic (``TypeVarTuple``) it is always
2716+
considered invariant. No further inference is needed.
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2719-
2. If the type parameter comes from a traditional ``TypeVar`` declaration and
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is not specified as ``infer_variance`` (see below), its variance is specified
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by the ``TypeVar`` constructor call. No further inference is needed.
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2. If the type parameter comes from a traditional ``TypeVar``/``ParamSpec``
2719+
declaration and is not specified as ``infer_variance`` (see below), its
2720+
variance is specified by the constructor call. No further inference is needed.
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3. Create two specialized versions of the class. We'll refer to these as
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``upper`` and ``lower`` specializations. In both of these specializations,

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