Fix auto import crashes caused by unrelocatable symbols

[andrewbranch]

Fixes #45030

Fixes two separate crashes—one was a simple overlooked case for skipping symbol property names, but the other was caused by a weird symbol merge that I think might be wrong/undesirable—I was expecting to see an alias in the exports of a module symbol, but instead got a merged resolved module symbol—see the comment below the second fourslash test.

[sandersn]

Why can't you include the weird merge? Is it because it doesn't have a usable name?

[andrewbranch]

Why can't you include the weird merge? Is it because it doesn't have a usable name?

Yes. I can include the weird merge, but it would either have bad performance characteristics or require a new/updated checker API to give me the keys along with the symbols when getting all exports and properties of a module, and would require some refactoring to store those in the cache and use them as lookups appropriately. That might be the way forward, but I wanted to get @weswigham’s opinion on whether this merge is valid/expected first.

[sandersn]

I vote to merge this to fix the crash if it's urgent; otherwise wait a few days to get @weswigham's read on whether the merge is expected and/or easy enough to fix.

[andrewbranch]

I’ll wait until tomorrow.

[weswigham]

It's an odd merge, but intentional - if we didn't merge (and we used to not) the interface augmentation would override the base member, rather than merge with it (which is unintuitive and undesirable).

[andrewbranch]

@weswigham but why replace the export alias symbol altogether? Could the alias not merge with the module augmentation, rather than the alias’s target (an external module)?

[andrewbranch]

Going to merge and file a bug for the missing case.