[clang] [C++][Modules] Import declaration should in global module fragment, module interface or module implementation (PR #164106)

[Hubert Tong via cfe-commits]

https://github.com/hubert-reinterpretcast commented:

I am unaware of any such restriction.
An _pp-import_ is a _control-line_, which is in turn a _group-part_.
A _preprocessing-file_ can directly contain a _group_ with being a _module-file_.

There _is_ a restriction on _pp-global-module-fragment_‌s: at the start of phase 4, they can contain neither a _pp-import_ nor a _text-line_.

https://github.com/llvm/llvm-project/pull/164106