fix: Treat NewType as their underlying runtime type #3337
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| // PY-85543: Treat typing.NewType instances as their underlying runtime type for assignability checks. | ||
| // NewType is only a static marker; at runtime it's the supertype, so unwrap it early. | ||
| if (actual instanceof PyTypingNewType typingNewType) { | ||
| actual = new PyClassTypeImpl(typingNewType.getPyClass(), typingNewType.isDefinition()); |
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Bug: Generic type parameters lost when unwrapping NewType
When actual is a PyTypingNewType, the code converts it to a new PyClassTypeImpl using only getPyClass() and isDefinition(). This discards generic type parameters if the underlying type is a PyCollectionType like Dict[str, int]. For example, NewType("KeyValue", dict[str, int]) would be treated as just dict, causing incorrect type matching where KeyValue values could incorrectly pass checks for dict[str, str]. The underlying classType holds the complete type information including generics, but this information is lost in the conversion.
python/python-psi-impl/src/com/jetbrains/python/psi/types/PyTypeChecker.java
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Also, keep type parameters
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Fixes https://youtrack.jetbrains.com/issue/PY-85543
Note
Unwrap
typing.NewTypeto its underlying class inPyTypeCheckermatching and add targeted tests (including generics and f-stringint()call).PyTypingNewTypeto its runtime supertype inPyTypeChecker.matchImplfor assignability checks, including handling NewType ancestry and early equality.testNewTypeAcceptedByIntCallInsideFStringandtestNewTypeWithGenericsinpython/testSrc/.../Py3TypeCheckerInspectionTest.java.python/testData/inspections/PyTypeCheckerInspection/NewTypeWithGenerics.pyverifyingNewTypewithDictgenerics.Written by Cursor Bugbot for commit f89130f. This will update automatically on new commits. Configure here.