Enhancement: The reportUnknownVariableType setting now also checks for unknown or partially-unknown types in return type declaration and return value expressions.
Enhancement: Added new setting reportUnknownArgumentType that emits an error or warning when an argument's expression type is unknown or partially unknown. This setting is enabled in strict mode.
Bug Fix: Changed type checker to enforce invariance of type arguments where appropriate. This includes union types.
Bug Fix: Fixed bug in bidirectional type inference in case where provided object was subclassed from the expected type's class.
Bug Fix: Fixed bug in speculative evaluation mode where cached types from older speculative sessions were still being used in newer speculative sessions, giving the wrong answer.
Bug Fix: Fixed logic for detecting abstract methods that are not overridden. The previous logic didn't work when a mix-in class provided the implementation.