Unparameterized use of generic types results in diagnostics

The current main branch has implementation in https://github.com/fastavro/fastavro/blob/master/fastavro/types.py which uses Python generic types (Dict, List) with insufficient type parameterization.

DictSchema = Dict
Schema = Union[str, List, DictSchema]
NamedSchemas = Dict[str, Dict]

When used with the pyright / pylance type checker, this effectively pollutes fastavro API usage with type warnings, as "Dict" is seen as "Dict[Unknown]".

I am aware of the existence of the "better_typing" branch at https://github.com/fastavro/fastavro/blob/better_typing/fastavro/types.py and do notice considerable effort going into providing comprehensive typing support.

Still, possibly as a temporary stop-gap measure, refactoring the existing implementation on main to use the Any type, for instance like

DictSchema = Dict[Any, Any]
Schema = Union[str, List[Any], DictSchema]
NamedSchemas = Dict[str, Dict[Any, Any]]

could make a lot of code "type-safe" simply by declaring "anything goes, don't know", effectively suppressing the type warnings at the library end. (cf https://docs.python.org/3/library/typing.html#the-any-type)

The Any type was introduced with Python 3.5, so it should be usable.

Happy to provide a PR if that is a way forward?

fastavro / fastavro

Unparameterized use of generic types results in diagnostics #797