Discrepancy between spec and tests on indexing TypedDicts with non-literal variables

Splitting issue from PR https://github.com/python/typing/pull/1978

Spec says that it should be generally rejected (ref)

A key that is not a literal should generally be rejected, since its value is unknown during type checking, and thus can cause some of the above violations.

But currently conformance tests do not reflect it.

https://github.com/python/typing/blob/2d88da2a407b556f5b52b4c6ad1bd659873bb9ac/conformance/tests/typeddicts_operations.py#L34-L38

So in theory to resolve this, either strictness should be reflected in conformance tests or spec should be amended allowing optional enforcement.

Related discussion - https://discuss.python.org/t/indexing-typeddict-with-a-non-literal-variable/88929

先从 TypedDict 操作规范部分以及第 34-38 行附近的 conformance/tests/typeddicts_operations.py 开始，然后阅读 PR 1978 和链接的讨论。确定一致性测试是否应拒绝非字面量索引，或者规范是否应允许可选强制执行。规范和一致性测试一致地描述约定的行为，即表示完成。