perry-stdlib symbols_tests::thread_exit_releases_the_threads_symbol_side_table_entries fails on main since #11682/#11683

[proggeramlug]

perry-stdlib's runtime_thread_exit_tests::symbols_tests::thread_exit_releases_the_threads_symbol_side_table_entries fails on a pristine main 23d563404. The command is RUST_TEST_THREADS=1 cargo test --release -p perry-stdlib -- symbols_tests on perrymaster, Linux x86_64, codegen-units 16:

panicked at crates/perry-stdlib/src/runtime_thread_exit_tests/symbols_tests.rs:135:5:
assertion `left == right` failed: every entry must exist while its thread lives
  left: [false, false, false, true]
 right: [true, true, true, true]

All three entries on the ordinary object are missing while their thread is still alive: the SYMBOL_PROPERTIES value, the SYMBOL_PROPERTY_ATTRS attribute and the SYMBOL_ACCESSOR_PROPERTIES accessor. Only the class-static entry is present. So the probe no longer finds an ordinary object's symbol properties in the address-keyed tables. They most likely live on the object now, and the test's premise (or its probes) needs updating.

The failure is not present at 7fa094cb4: main's run 36633236189 cargo-test failed only on the unrelated issue_10058_push_spread_scaling. So it arrived with #11682 or #11683 ("honest handles").

Found while triaging #11676. That PR's branch fails identically.

[proggeramlug]

Bisected on perrymaster (release, codegen-units 16, RUST_TEST_THREADS=1 cargo test --release -p perry-stdlib -- symbols_tests):

• 7fa094cb4 (parent of honest handles: EventTarget family are real objects; built-in constructor statics read the constructor #11682): 10/10 pass.
• b67ad0005 (honest handles: EventTarget family are real objects; built-in constructor statics read the constructor #11682, "honest handles: EventTarget family are real objects"): this test fails with left: [false, false, false, true].

So the culprit is #11682, not #11683. #11682 adds object/shaped_symbols.rs, so ordinary objects' symbol properties no longer go into the address-keyed SYMBOL_PROPERTIES / SYMBOL_PROPERTY_ATTRS / SYMBOL_ACCESSOR_PROPERTIES tables that the test probes. #11682's own PR CI already showed cargo-test red.

[proggeramlug]

Fixed by #11702.