C++ types declared within unimportable type are not imported

[egorzhdan]

The MLIRContext C++ type is not imported into Swift by default, because is has a deleted copy constructor: https://github.com/llvm/llvm-project/blob/f0cd5389850589fbf8a3ce77cea2539579bd8028/mlir/include/mlir/IR/MLIRContext.h#L55

However, another type (Threading) declared within MLIRContext is not imported, even though there is nothing preventing Swift from importing it.
https://github.com/llvm/llvm-project/blob/f0cd5389850589fbf8a3ce77cea2539579bd8028/mlir/include/mlir/IR/MLIRContext.h#L57

Can Swift treat MLIRContext as a namespace in this case, importing it as an enum with no cases?