[clang] [clang] Fix loss of `dllexport` for exported template specialization (PR #93302)

[Andrew Ng via cfe-commits]

nga888 wrote:

Ok, I have confirmed that the `getMostRecentDecl()` fix does indeed work on the `main` branch. When I started debugging this issue sometime ago, I was working with a downstream branch based off `17.x` using the source file from UE 5.4. I remember trying the use of `getMostRecentDecl()` but it did not work. I thought that it had failed to fix this specific issue but on retrying the fix, it does fix the test case from this patch (haven't retested with UE 5.4 itself). However, this fix also causes a `dllimport` test to fail too, so perhaps that was the "failure" that I encountered, I just don't remember. The same also applies to `18.x`. However, interestingly, this `dllimport` test does not fail on the `main` branch, I think because of other changes since `18.x`, but this does make me feel a little uneasy.

The code changes in this patch have been tested across `17.x`, `18.x` and `main` with no "extra" issues.

@zmodem, how would you like to proceed? If the removal of the dropping of `dllexport` is not acceptable, then I guess a new PR based on a fix using `getMostRecentDecl()`?


https://github.com/llvm/llvm-project/pull/93302