Fix issue #34101

[pnkfelix]

Fix issue #34101: do not track subcontent of type with dtor nor gather flags for untracked content.

(Includes a regression test, which needed to go into compile-fail/
due to weaknesses when combining #[deny(warnings)] with
tcx.sess.span_warn(..))

[rust-highfive]

r? @jroesch

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[pnkfelix]

r? @arielb1

[pnkfelix]

This patch was meant to be a somewhat minimal change to the code in question, at the potential cost of wasting compilation time evaluating lvalue_is_tracked on each call to path_needs_drop.

I am assuming that the recursive chain there almost never gets terribly long in most (human-generated) code. But its worth keeping an eye on, and I'm open to alternative suggestions.

[arielb1]

@pnkfelix

I would rather have that logic inside is_terminal rather than path_needs_drop. That's what I added it for.

Maybe also add a soft assertion that all non-DropAndReplace drops are of tracked data?

r+ modulo that

[arielb1]

*differs from

[pnkfelix]

@arielb1 oh good: I think moving the logic into fn is_terminal_path allows me to avoid adding the recursive walk up the parent chain that I was concerned about.

[pnkfelix]

@bors r=arielb1

[bors]

📌 Commit 4b6a68e has been approved by arielb1

[pnkfelix]

hmm actually I think this patch might break -Z orbit

[pnkfelix]

In particular:

run-pass/issue-4401.rs regresses (when compiled without -O):

% rustc -Z orbit ../src/test/run-pass/issue-4401.rs
% ./issue-4401 999999
% ./x86_64-apple-darwin/stage1/bin/rustc -Z orbit ../src/test/run-pass/issue-4401.rs
% ./issue-4401 thread 'main' has overflowed its stack
fatal runtime error: stack overflow
Abort trap: 6
% 

(I also saw a failure associated with run-pass/issue-28950.rs, but that seems to also segfault without this PR under -Z orbit, so I'm ignoring it for now...)

[pnkfelix]

ah, problem appears fixed when I rebase atop PR #34128 ; crisis averted, thanks @eddyb !

[bors]

⌛ Testing commit 4b6a68e with merge 33c8992...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-32cross-opt, auto-linux-64-cargotest, auto-linux-64-cross-armhf, auto-linux-64-cross-armsf, auto-linux-64-cross-freebsd, auto-linux-64-cross-netbsd, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-mir, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-mac-64-opt-rustbuild, auto-mac-cross-ios-opt, auto-win-gnu-32-nopt-t, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-nopt-t, auto-win-gnu-64-opt, auto-win-msvc-32-cross-opt, auto-win-msvc-32-opt, auto-win-msvc-64-cargotest, auto-win-msvc-64-opt, auto-win-msvc-64-opt-mir, auto-win-msvc-64-opt-rustbuild