Enhancement: Reimplemented handling of f-strings in accordance with PEP 701, which is included in Python 3.12.0b1. This is a significant change with potential for regressions.
Enhancement: Implemented ReadOnly TypedDict fields to explore proposed PEP 705 variant as discussed in this discussion thread. This prototype will help inform which direction to take with PEP 705.
Bug Fix: Fixed regression that caused an internal assertion (and therefore a crash) when type checking a constructor whose arguments are not type compatible.
Bug Fix: Fixed bug that led to a "leaked" unsolved type variable if a __new__ method used a function-scoped type variable and there was no __init__ method for the class.
Enhancement: A class created with "NewType" should be treated as though it is implicitly @final. The runtime enforces this. Pyright now correctly generates an error if such a class is used as a base class.
Bug Fix: Fixed a false positive error with the reportImplicitOverride check that occurs when the @override decorator is applied to a method that is decorated with a wrapper function that completely replaces the original function with another.
Bug Fix: Fixed places in the pyright code where lists were being expanded on the stack, resulting in a stack overflow (and therefore a crash) if the list is too large.
Enhancement: Added special-case synthesis of the update method for a TypedDict class. For TypedDicts that include at least one read-only field, no updates are allowed. For TypedDicts that are writable, a "partial" type is synthesized that allows for any subset of keys (required or not required) to be passed to the update method.
Behavior Change: Changed protocol matching behavior for protocols that include a variable annotated as ClassVar. A class that defines this same variable as a "regular class variable" (one that is declared at the class level but can be overwritten on a per-instance basis) is now considered compatible with such a protocol.
Behavior Change: Changed type narrowing on assignment for member access expressions that involve an asymmetric __getattr__ and __setattr__ method. As with asymmetric descriptors, it is not safe in this case to assume that the written value will be the same as the read value.
Bug Fix: Fixed a bug that led to a false positive error in certain circumstances with nested call expressions where the expected type of the parameter was a union.
Behavior Change: Changed the behavior when a parameter whose type is a "naked" TypeVar has a default argument value. Mypy doesn't allow this case. Pyright allows it but previously modified the parameter type to be a union of the TypeVar and the type of the default argument. This behavior closed some type validation holes, but it created other problems and was very unintuitive for users. See #3130. See #2507 for a discussion that led to this original change. This change reverses this behavior. It potentially allows for some unsafe "creative" uses that will go unreported.
Bug Fix: Fixed recent regression that caused useLibraryCodeForTypes setting not to be applied if it was specified in the language server settings (as opposed to the config file).
Enhancement: Updated typeshed stubs to the latest version.
Bug Fix: Fixed bug that resulted in a false positive error when the "expected type" for a lambda is a function that includes a ParamSpec.
Bug Fix (thanks to @LyricLy for the contribution!): Preserve parentheses around unary operators for printing.
Bug Fix: Fixed a couple of bugs in the method override consistency check that resulted in false positives when ParamSpecs were involved.
Bug Fix: Fixed bug that led to the incorrect type evaluation of an async generator when an await operator was used within a nested expression.
Performance: Addressed a performance issue that occurs when analyzing complex functions with deeply nested lambdas. This change adds a more sophisticated type caching mechanism that avoids emptying the cache when analyzing lambdas.
Performance: Added perf optimization to stripLiteralValue method to handle large unions comprised only of literal values.
Performance: Modified constraint solver to limit the number of subtypes in a union for the narrow bound of a type variable. Under certain rare circumstances, this can grow to a very large number and cause perf issues and hangs.
Bug Fix: Fixed a bug that caused an internal cache to be corrupted leading to a false positive error in specific circumstances.