Consider adding a "TopLevel" keyword that stands in for the top level bound of a corresponding type variable

Summary

Please consider a new typing keyword that stands in for the top level type of a corresponding type variable.

Motivation

Consider a test here and the corresponding definition of DistributionInfo here. The test loses all typing information because I used DistributionInfo[Any, Any, Any]. So if I want typing information, I have to use:

def test_flatten(generator: Generator,
                 distribution_info: DistributionInfo[NaturalParametrization[ExpectationParmetrization, JaxComplexArray],
                                                     ExpectationParametrization[NaturalParmetrization],
                                                     NumpyComplexArray]) -> None:

I would much rather just do

def test_flatten(generator: Generator,
                 distribution_info: DistributionInfo[TopLevel, TopLevel, TopLevel]) -> None:

It's not just shorter, but it reduces churn if the type definitions change. Note that TopLevel is recursive (it chooses the top level of the nested types too).

从链接的 tests/test_flatten.py 和 tests/distribution_info.py 开始，了解使用 DistributionInfo[Any, Any, Any] 时会丢失哪些类型信息。明确 TopLevel 的预期递归语义，以及它与现有类型变量行为的区别。当提案包含精确的规范和已达成一致的验证路径时，即视为完成。