Due to an oversight, when users use an unexported declaration from
implicit global module, the diagnostic will show "please #include"
instead of "please import". This patch corrects the behavior.
Also previously, when users use an unexported declarations from module
partitions, the diagnostic message will always show the partition name
no matter if that partition name is visible to the users. Now the users
may only see the partition name if the users are in the same module with
the partition unit.
Now the implementation would accept following code:
```
//--- impl.cppm
module M:impl;
class A {};
//--- M.cppm
export module M;
import :impl;
//--- Use.cpp
import M;
void test() {
A a; // Expected error. A is not visible here.
}
```
which is clearly wrong. The root cause is the implementation of
`isInCurrentModule` would return true if the module is a partition! So
in the above example, although Use.cpp is not a module unit,
`isInCurrentModule ` would still return true when the compiler tries to
see if the owning module of `A` is the current module. I believe this is
an oversight. This patch tries to fix this problem.
Reviewed By: iains
Differential Revision: https://reviews.llvm.org/D123837
