Pyright

New Feature: Extended type constraint logic for isinstance calls that pass a tuple of types for the second parameter.
New Feature: Improved definition provider ("show definitions") to handle multiple declarations. This occurs when overrides are used and when a member is declared in different places for types in a union.
New Feature: Types used for TypeVar bound and constraint types are now validated to ensure that they are not generic (i.e. use other TypeVars).
New Feature: Implemented proper type inference for dictionary literals that use list comprehensions.
New Feature: Annotated types for function parameters are now enforced, so an attempt to reassign the parameter will generate an error if the assigned value doesn't match the annotated type.
Bug Fix: Fixed reported bug with specialized type aliases.
Bug Fix: Type constraint logic was not properly handling the case where an assignment targeted a property.
Bug Fix: Imports of the form "from . import X" are now properly checked, and an error is reported if X doesn't exist.

New Feature: Type checker now honors type annotations on `*args` and `**kwargs` function parameters.
New Feature: Changed the way assignments are handled when the target of the assignment has a declared type. The type checker now uses the source (RHS) of the assignment to constrain the declared type if it is a union.
Bug Fix: Unbound or potentially-unbound variables are once again flagged as such.
Bug Fix: Fixed type inference for instantiation of generic class based on arguments passed to its constructor or init routine.
Bug Fix: Fixed several bugs relating to list comprehension type analysis.
Bug Fix: Fixed code flow analysis logic for for/else statements.
Bug Fix: Arguments with a literal type need to be "genericized" before performing type var matching on generic functions.
Bug Fix: Literal types with a value of 0 or empty string were not being printed as a literal in error messages.
Bug Fix: Fixed another bug in the datetime.pyi typeshed stub file relating to the `datetime.combine` method.
Bug Fix: Fixed a bug in the builtins.pyi typeshed stub file in the `tuple.__add__` method. It required that the parameter be of the same tuple type.

New Feature: Added support for Literal type in typing_extensions.
New Feature: Added typing_extensions.pyi fallback type stub file.
New Feature: Types for arg and kwarg parameters are now correctly inferred to be of type List[X] and Dict[str, X] where X is either specified by the type annotation or assumed to be Unknown.
New Feature: Added type constraint logic for expressions of the form "type(X) is Y" and "type(X) is not Y".
New Feature: Added validation for ClassVar parameters to ensure that it doesn't contain any type variables.
Bug Fix: Fixed bug in "datetime.combine" method in datetime.pyi typeshed type stub.
Bug Fix: Type checker was not properly handling assignments where the LHS was a tuple and the RHS was an utterable type.
Improved responsiveness of VS Code extension.

Bug Fix: Fixed bad regression introduced in 1.0.20 where imported modules that are imported with the `import xyz` statement (as opposed to the `from xyz import abc` form) are reported as 'unbound'. This occurs only if there is no type stub file found for that import.

New Feature: Added "reportUntypedNamedTuple" config switch for reporting the use of "namedtuple", which is an untyped version of "NamedTuple".
New Feature: Added type inference support for list comprehension statements.
New Feature: Improved type inference when indexing into a tuple type with a constant integer index. It now uses the appropriate type for that tuple entry if it's known.
Bug Fix 101: Type inference engine now infers a return type of Generator[Y] for generator functions rather than Iterator[Y].
Bug Fix: Fixed bug that masked type checking operations for certain built-in types like List and Dict.
Bug Fix: For statements now allow iterators that provide `__getitem__`, as per PEP 234.
Bug Fix: Fixed an issue where classes defined with NamedTuple were not providing correct type checks.
Bug Fix: Fixed bug in completion handler that caused completion recommendations to appear when pressing period within a comment.
Bug Fix: Pyright was failing to search beyond the first search path when using fall-back paths from the python interpreter.

This release includes a significant set of changes to the core type engine that are required to enable the next round of functionality. I've done my best to avoid introducing regressions, but they are possible in a change of this size.
One known regression is that unbound or potentially-unbound variables are no longer flagged in many cases.

New Feature: Added new config switch "reportUnknownParameterType" that reports input and return parameters with an unknown type.
New Feature: Added new config switch "reportUnknownVariableType" that reports local variables with an unknown type.
New Feature: Added new config switch "reportUnknownMemberType" that reports class members (instance variables and class variables) with an unknown type.
New Feature: Further improved logging to diagnose import failures.
New Feature: Added "strict mode" that can be enabled on a per-file basis by adding the comment " pyright: strict". This enables all type-checking configuration flags for that file.
New Feature: Added support in type check engine for expression type constraints involving the "or" operator.
Bug Fix 91: Added code to convert file specs passed to command-line from relative to absolute.
Bug Fix: Added code path lookups for both "lib" and "Lib" within virtual environment to accommodate capitalization convention on Windows.
Bug Fix: Removed limitation that type annotation strings not use bytes, unicode or raw strings.