rust-demangler tool strips crate disambiguators with < 16 digits

[richkadel]

Addresses Issue #77615.

[rust-highfive]

r? @Mark-Simulacrum

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[Mark-Simulacrum]

I did not know we had this in tree and am unsure of what exactly it's used for (I guess I can look). r? @eddyb for now though.

[richkadel]

I added the tool a while back. It supports llvm-cov coverage tool's option to use an external demangler when generating coverage reports.

[richkadel]

Just FYI... @wesleywiser @tmandry

This is the PR to resolve the bug report against AArch64 (though I think the bug isn't really specific to that architecture, and could get triggered on any platform depending on the generated hash value).

[tmandry]

It seems pretty clear now that this is a heuristic to remove disambiguators, even if it's one that's very likely to succeed.

That does seem acceptable for the tests we're using it for, but maybe not for everything. I think we should document that it's using a heuristic in the doc comment and help text, just so people know about it before they take on a dependency.

@bors delegate+
r=tmandry when done

[bors]

✌️ @richkadel can now approve this pull request

[richkadel]

I'll make the additional changes before submitting to bors. Thanks!

[richkadel]

@bors r=tmandry

[bors]

📌 Commit 796e6ac has been approved by tmandry

[bors]

⌛ Testing commit 796e6ac with merge 9a74fb7...

[bors]

☀️ Test successful - checks-actions, checks-azure
Approved by: tmandry
Pushing 9a74fb7 to master...