[clang] [clang][Modules] Reject export declarations in implementation partitions (PR #188698)

[Chuanqi Xu via cfe-commits]

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@@ -9931,9 +9914,10 @@ class Sema final : public SemaBase {
 
   /// Is the module scope we are an implementation unit?
   bool currentModuleIsImplementation() const {
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ChuanqiXu9 wrote:

Let's not touch this. Module implementation unit and Module Partition Implementation Unit have very different properties. Let's not mixing them if possible.

We should judge if it is interface unit at the diganosing point.

https://github.com/llvm/llvm-project/pull/188698