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specify that type variable tuple should have variance
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‎conformance/results/mypy/generics_typevartuple_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 35: Expected 1 errors
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Line 41: Expected 1 errors
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Line 23: Unexpected errors ['generics_typevartuple_variance.py:23: error: Incompatible types in assignment (expression has type "CovariantTypeVarTuple[[int]]", variable has type "CovariantTypeVarTuple[[object]]") [assignment]']
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Line 26: Unexpected errors ['generics_typevartuple_variance.py:26: error: Unexpected keyword argument "contravariant" for "TypeVarTuple" [misc]']
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Line 34: Unexpected errors ['generics_typevartuple_variance.py:34: error: Incompatible types in assignment (expression has type "ContravariantTypeVarTupleOld[object]", variable has type "ContravariantTypeVarTupleOld[int]") [assignment]']
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Line 37: Unexpected errors ['generics_typevartuple_variance.py:37: error: Unexpected keyword argument "covariant" for "TypeVarTuple" [misc]']
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Line 42: Unexpected errors ['generics_typevartuple_variance.py:42: error: Missing return statement [empty-body]']
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"""
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output = """
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generics_typevartuple_variance.py:15: error: Incompatible types in assignment (expression has type "ContravariantTypeVarTuple[[int]]", variable has type "ContravariantTypeVarTuple[[object]]") [assignment]
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generics_typevartuple_variance.py:23: error: Incompatible types in assignment (expression has type "CovariantTypeVarTuple[[int]]", variable has type "CovariantTypeVarTuple[[object]]") [assignment]
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generics_typevartuple_variance.py:26: error: Unexpected keyword argument "contravariant" for "TypeVarTuple" [misc]
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generics_typevartuple_variance.py:31: error: Missing return statement [empty-body]
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generics_typevartuple_variance.py:34: error: Incompatible types in assignment (expression has type "ContravariantTypeVarTupleOld[object]", variable has type "ContravariantTypeVarTupleOld[int]") [assignment]
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generics_typevartuple_variance.py:37: error: Unexpected keyword argument "covariant" for "TypeVarTuple" [misc]
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generics_typevartuple_variance.py:42: error: Missing return statement [empty-body]
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generics_typevartuple_variance.py:47: error: Incompatible types in assignment (expression has type "CovariantTypeVarTupleOld[object]", variable has type "CovariantTypeVarTupleOld[int]") [assignment]
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"""

‎conformance/results/pyrefly/generics_typevartuple_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 ['`ContravariantTypeVarTuple[[object]]` is not assignable to `ContravariantTypeVarTuple[[int]]` [bad-assignment]']
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Line 23: Unexpected errors ['`CovariantTypeVarTuple[[int]]` is not assignable to `CovariantTypeVarTuple[[object]]` [bad-assignment]']
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Line 26: Unexpected errors ['Unexpected keyword argument `contravariant` to TypeVarTuple [invalid-type-var-tuple]']
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Line 34: Unexpected errors ['`ContravariantTypeVarTupleOld[object]` is not assignable to `ContravariantTypeVarTupleOld[int]` [bad-assignment]']
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Line 37: Unexpected errors ['Unexpected keyword argument `covariant` to TypeVarTuple [invalid-type-var-tuple]']
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Line 46: Unexpected errors ['`CovariantTypeVarTupleOld[int]` is not assignable to `CovariantTypeVarTupleOld[object]` [bad-assignment]']
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"""
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output = """
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ERROR generics_typevartuple_variance.py:14:42-48: `ContravariantTypeVarTuple[[object]]` is not assignable to `ContravariantTypeVarTuple[[int]]` [bad-assignment]
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ERROR generics_typevartuple_variance.py:23:42-49: `CovariantTypeVarTuple[[int]]` is not assignable to `CovariantTypeVarTuple[[object]]` [bad-assignment]
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ERROR generics_typevartuple_variance.py:26:29-47: Unexpected keyword argument `contravariant` to TypeVarTuple [invalid-type-var-tuple]
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ERROR generics_typevartuple_variance.py:34:49-59: `ContravariantTypeVarTupleOld[object]` is not assignable to `ContravariantTypeVarTupleOld[int]` [bad-assignment]
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ERROR generics_typevartuple_variance.py:35:14-24: `ContravariantTypeVarTupleOld[int]` is not assignable to variable `in_obj_old` with type `ContravariantTypeVarTupleOld[object]` [bad-assignment]
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ERROR generics_typevartuple_variance.py:37:31-45: Unexpected keyword argument `covariant` to TypeVarTuple [invalid-type-var-tuple]
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ERROR generics_typevartuple_variance.py:46:49-60: `CovariantTypeVarTupleOld[int]` is not assignable to `CovariantTypeVarTupleOld[object]` [bad-assignment]
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ERROR generics_typevartuple_variance.py:47:15-26: `CovariantTypeVarTupleOld[object]` is not assignable to variable `out_int_old` with type `CovariantTypeVarTupleOld[int]` [bad-assignment]
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"""

‎conformance/results/pyright/generics_typevartuple_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_typevartuple_variance.py:14:42 - error: Type "ContravariantTypeVarTuple[(object)]" is not assignable to declared type "ContravariantTypeVarTuple[(int)]"']
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Line 23: Unexpected errors ['generics_typevartuple_variance.py:23:42 - error: Type "CovariantTypeVarTuple[(int)]" is not assignable to declared type "CovariantTypeVarTuple[(object)]"']
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Line 26: Unexpected errors ['generics_typevartuple_variance.py:26:29 - error: "contravariant" is unknown parameter to TypeVarTuple (reportGeneralTypeIssues)']
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Line 34: Unexpected errors ['generics_typevartuple_variance.py:34:49 - error: Type "ContravariantTypeVarTupleOld[object]" is not assignable to declared type "ContravariantTypeVarTupleOld[int]"']
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Line 37: Unexpected errors ['generics_typevartuple_variance.py:37:31 - error: "covariant" is unknown parameter to TypeVarTuple (reportGeneralTypeIssues)']
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Line 46: Unexpected errors ['generics_typevartuple_variance.py:46:49 - error: Type "CovariantTypeVarTupleOld[int]" is not assignable to declared type "CovariantTypeVarTupleOld[object]"']
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"""
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output = """
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generics_typevartuple_variance.py:14:42 - error: Type "ContravariantTypeVarTuple[(object)]" is not assignable to declared type "ContravariantTypeVarTuple[(int)]"
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  "ContravariantTypeVarTuple[(object)]" is not assignable to "ContravariantTypeVarTuple[(int)]"
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    Type parameter "InTs@ContravariantTypeVarTuple" is invariant, but "(object)" is not the same as "(int)" (reportAssignmentType)
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generics_typevartuple_variance.py:15:10 - error: Type "ContravariantTypeVarTuple[(int)]" is not assignable to declared type "ContravariantTypeVarTuple[(object)]"
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  "ContravariantTypeVarTuple[(int)]" is not assignable to "ContravariantTypeVarTuple[(object)]"
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    Type parameter "InTs@ContravariantTypeVarTuple" is invariant, but "(int)" is not the same as "(object)" (reportAssignmentType)
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generics_typevartuple_variance.py:23:42 - error: Type "CovariantTypeVarTuple[(int)]" is not assignable to declared type "CovariantTypeVarTuple[(object)]"
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  "CovariantTypeVarTuple[(int)]" is not assignable to "CovariantTypeVarTuple[(object)]"
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    Type parameter "OutTs@CovariantTypeVarTuple" is invariant, but "(int)" is not the same as "(object)" (reportAssignmentType)
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generics_typevartuple_variance.py:24:11 - error: Type "CovariantTypeVarTuple[(object)]" is not assignable to declared type "CovariantTypeVarTuple[(int)]"
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  "CovariantTypeVarTuple[(object)]" is not assignable to "CovariantTypeVarTuple[(int)]"
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    Type parameter "OutTs@CovariantTypeVarTuple" is invariant, but "(object)" is not the same as "(int)" (reportAssignmentType)
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generics_typevartuple_variance.py:26:29 - error: "contravariant" is unknown parameter to TypeVarTuple (reportGeneralTypeIssues)
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generics_typevartuple_variance.py:34:49 - error: Type "ContravariantTypeVarTupleOld[object]" is not assignable to declared type "ContravariantTypeVarTupleOld[int]"
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  "ContravariantTypeVarTupleOld[object]" is not assignable to "ContravariantTypeVarTupleOld[int]"
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    Type parameter "InTs@ContravariantTypeVarTupleOld" is invariant, but "*tuple[object]" is not the same as "*tuple[int]" (reportAssignmentType)
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generics_typevartuple_variance.py:35:14 - error: Type "ContravariantTypeVarTupleOld[int]" is not assignable to declared type "ContravariantTypeVarTupleOld[object]"
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  "ContravariantTypeVarTupleOld[int]" is not assignable to "ContravariantTypeVarTupleOld[object]"
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    Type parameter "InTs@ContravariantTypeVarTupleOld" is invariant, but "*tuple[int]" is not the same as "*tuple[object]" (reportAssignmentType)
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generics_typevartuple_variance.py:37:31 - error: "covariant" is unknown parameter to TypeVarTuple (reportGeneralTypeIssues)
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generics_typevartuple_variance.py:46:49 - error: Type "CovariantTypeVarTupleOld[int]" is not assignable to declared type "CovariantTypeVarTupleOld[object]"
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  "CovariantTypeVarTupleOld[int]" is not assignable to "CovariantTypeVarTupleOld[object]"
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    Type parameter "OutTs@CovariantTypeVarTupleOld" is invariant, but "*tuple[int]" is not the same as "*tuple[object]" (reportAssignmentType)
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generics_typevartuple_variance.py:47:15 - error: Type "CovariantTypeVarTupleOld[object]" is not assignable to declared type "CovariantTypeVarTupleOld[int]"
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  "CovariantTypeVarTupleOld[object]" is not assignable to "CovariantTypeVarTupleOld[int]"
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    Type parameter "OutTs@CovariantTypeVarTupleOld" is invariant, but "*tuple[object]" is not the same as "*tuple[int]" (reportAssignmentType)
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"""

‎conformance/results/results.html‎

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@@ -468,6 +468,13 @@ <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 not-conformant">Unsupported</th>
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</tr>
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<tr><th class="column col1">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;generics_typevartuple_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_upper_bound</th>
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<th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Does not reject use of type variable within an upper bound.</p></span></div></th>
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<th class="column col2 conformant">Pass</th>

‎conformance/results/ty/generics_typevartuple_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 41: Expected 1 errors
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Line 47: Expected 1 errors
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Line 26: Unexpected errors ['generics_typevartuple_variance.py:26:29: error[unknown-argument] Argument `contravariant` does not match any known parameter of function `__new__`']
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Line 37: Unexpected errors ['generics_typevartuple_variance.py:37:31: error[unknown-argument] Argument `covariant` does not match any known parameter of function `__new__`']
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Line 42: Unexpected errors ['generics_typevartuple_variance.py:42:24: error[empty-body] Function always implicitly returns `None`, which is not assignable to return type `tuple[@Todo(TypeVarTuple), ...]`']
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"""
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output = """
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generics_typevartuple_variance.py:26:29: error[unknown-argument] Argument `contravariant` does not match any known parameter of function `__new__`
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generics_typevartuple_variance.py:31:24: error[empty-body] Function always implicitly returns `None`, which is not assignable to return type `tuple[@Todo(TypeVarTuple), ...]`
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generics_typevartuple_variance.py:37:31: error[unknown-argument] Argument `covariant` does not match any known parameter of function `__new__`
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generics_typevartuple_variance.py:42:24: error[empty-body] Function always implicitly returns `None`, which is not assignable to return type `tuple[@Todo(TypeVarTuple), ...]`
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"""

‎conformance/results/zuban/generics_typevartuple_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 35: Expected 1 errors
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Line 41: Expected 1 errors
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Line 23: Unexpected errors ['generics_typevartuple_variance.py:23: error: Incompatible types in assignment (expression has type "CovariantTypeVarTuple[[int]]", variable has type "CovariantTypeVarTuple[[object]]") [assignment]']
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Line 26: Unexpected errors ['generics_typevartuple_variance.py:26: error: Unexpected keyword argument "contravariant" for "TypeVarTuple" [call-arg]']
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Line 34: Unexpected errors ['generics_typevartuple_variance.py:34: error: Incompatible types in assignment (expression has type "ContravariantTypeVarTupleOld[object]", variable has type "ContravariantTypeVarTupleOld[int]") [assignment]']
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Line 37: Unexpected errors ['generics_typevartuple_variance.py:37: error: Unexpected keyword argument "covariant" for "TypeVarTuple" [call-arg]']
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Line 42: Unexpected errors ['generics_typevartuple_variance.py:42: error: Missing return statement [empty-body]']
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"""
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output = """
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generics_typevartuple_variance.py:15: error: Incompatible types in assignment (expression has type "ContravariantTypeVarTuple[[int]]", variable has type "ContravariantTypeVarTuple[[object]]") [assignment]
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generics_typevartuple_variance.py:23: error: Incompatible types in assignment (expression has type "CovariantTypeVarTuple[[int]]", variable has type "CovariantTypeVarTuple[[object]]") [assignment]
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generics_typevartuple_variance.py:26: error: Unexpected keyword argument "contravariant" for "TypeVarTuple" [call-arg]
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generics_typevartuple_variance.py:31: error: Missing return statement [empty-body]
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generics_typevartuple_variance.py:34: error: Incompatible types in assignment (expression has type "ContravariantTypeVarTupleOld[object]", variable has type "ContravariantTypeVarTupleOld[int]") [assignment]
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generics_typevartuple_variance.py:37: error: Unexpected keyword argument "covariant" for "TypeVarTuple" [call-arg]
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generics_typevartuple_variance.py:42: error: Missing return statement [empty-body]
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generics_typevartuple_variance.py:47: error: Incompatible types in assignment (expression has type "CovariantTypeVarTupleOld[object]", variable has type "CovariantTypeVarTupleOld[int]") [assignment]
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"""

‎conformance/tests/generics_typevartuple_variance.py‎

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"""
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Tests variance of TypeVarTuple.
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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, TypeVarTuple
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class ContravariantTypeVarTuple[**InTs]:
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def f(self, *args: InTs.args, **kwargs: InTs.kwargs): ...
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in_obj: ContravariantTypeVarTuple[object] = ContravariantTypeVarTuple()
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in_int: ContravariantTypeVarTuple[int] = in_obj # OK
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in_obj = in_int # E
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class CovariantTypeVarTuple[**OutTs]:
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def f(self, fn: Callable[OutTs, None]) -> None: ...
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out_int: CovariantTypeVarTuple[int] = CovariantTypeVarTuple()
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out_obj: CovariantTypeVarTuple[object] = out_int # OK
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out_int = out_obj # E
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InTs = TypeVarTuple("InTs", contravariant=True)
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class ContravariantTypeVarTupleOld(Generic[*InTs]):
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def in_f(self, *args: *InTs) -> None: ... # OK
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def out_f(self) -> tuple[*InTs]: ... # E
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in_obj_old: ContravariantTypeVarTupleOld[object] = ContravariantTypeVarTupleOld()
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in_int_old: ContravariantTypeVarTupleOld[int] = in_obj_old # OK
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in_obj_old = in_int_old # E
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OutTs = TypeVarTuple("OutTs", covariant=True)
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class CovariantTypeVarTupleOld(Generic[*OutTs]):
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def in_f(self, *args: *OutTs) -> None: ... # E
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def out_f(self) -> tuple[*OutTs]: ... # OK
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out_int_old: CovariantTypeVarTupleOld[int] = CovariantTypeVarTupleOld()
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out_obj_old: CovariantTypeVarTupleOld[object] = out_int_old # OK
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out_int_old = out_obj_old # E

‎docs/spec/generics.rst‎

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@@ -1189,12 +1189,11 @@ for two reasons:
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* To improve readability: the star also functions as an explicit visual
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indicator that the type variable tuple is not a normal type variable.
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1192-
Variance, Type Constraints and Type Bounds: Not Supported
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Type Constraints and Type Bounds: Not Supported
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"""""""""""""""""""""""""""""""""""""""""""""""""""""""""
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11951195
``TypeVarTuple`` does not currently support specification of:
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1197-
* Variance (e.g. ``TypeVar('T', covariant=True)``)
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* Type constraints (``TypeVar('T', int, float)``)
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* Type bounds (``TypeVar('T', bound=ParentClass)``)
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@@ -2712,14 +2711,12 @@ The algorithm for computing the variance of a type parameter is as follows.
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27132712
For each type parameter in a generic class:
27142713

2715-
1. If the type parameter is variadic (``TypeVarTuple``) it is always
2716-
considered invariant. No further inference is needed.
2714+
1. If the type parameter comes from a traditional
2715+
``TypeVar``/``TypeVarTuple``/``ParamSpec`` declaration and is not specified
2716+
as ``infer_variance`` (see below), its variance is specified by the
2717+
constructor call. No further inference is needed.
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2718-
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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2722-
3. Create two specialized versions of the class. We'll refer to these as
2719+
2. 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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replace all type parameters other than the one being inferred by a dummy type
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instance (a concrete anonymous class that is assumed to meet the bounds or
@@ -2729,7 +2726,7 @@ specialization ignores the type parameter's upper bound or constraints. In the
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``lower`` specialized class, specialize the target type parameter with itself
27302727
(i.e. the corresponding type argument is the type parameter itself).
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2732-
4. Determine whether ``lower`` can be assigned to ``upper`` using normal
2729+
3. Determine whether ``lower`` can be assigned to ``upper`` using normal
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assignability rules. If so, the target type parameter is covariant. If not,
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determine whether ``upper`` can be assigned to ``lower``. If so, the target
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type parameter is contravariant. If neither of these combinations are

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