release blocker: #9169 regresses 4 gap tests (built-in iterator/prototype dispatch)

[proggeramlug]

Release blocker

main is red on 4 gap tests that are expected to pass (none is listed in test-parity/gap_snapshot.json). This blocks the v0.5.1519 release: any candidate refreshed from current main inherits these failures.

• test_gap_iterator_helpers_2874
• test_gap_language_types_object_part_a
• test_gap_object_string_wrappers
• test_gap_5592_class_expr_rebind_computed_accessor

Attribution — single-commit bisect, verified good endpoint

test	a722b4cca2 (parent)	89cde4ff14 (#9169)
test_gap_iterator_helpers_2874	PASS	FAIL
test_gap_language_types_object_part_a	PASS	FAIL
test_gap_object_string_wrappers	PASS	FAIL
test_gap_5592_class_expr_rebind_computed_accessor	PASS	FAIL

The good endpoint was run before being used as a baseline: all four pass at a722b4cca2.

Also verified these are NOT caused by PR #9242 (which CI blamed): with #9242's codegen change fully reverted on top of 89cde4ff14, all four still fail. #9242's only effect on this set is turning test_issue_945_scalar_method_guards from FAIL to PASS.

Why it reached main

gap-suite-build on #9169 did not complete (The operation was canceled), so every dependent gap shard was skipped. Nothing evaluated these tests before the merge.

Reproduction

cargo build --profile perry-dev -p perry -p perry-runtime-static -p perry-stdlib-static
PERRY_SKIP_BUILD=1 PERRY_BIN="$PWD/target/perry-dev/perry" \
PERRY_RUNTIME_DIR="$PWD/target/perry-dev" PERRY_NO_AUTO_OPTIMIZE=1 \
./run_parity_tests.sh --filter test_gap_iterator_helpers_2874

Observed for test_gap_iterator_helpers_2874 — Perry stops after the third line:

function
function
[ 1, 2, 3 ]
TypeError: undefined is not iterable

Node continues with [ 2, 4, 6 ], [ 2, 3 ], … The failing expression is [...gen().map((x) => x * 2)]: an iterator-helper method on a generator's prototype chain returns undefined.

Suspected surface

#9169 changed exactly the dispatch surfaces these tests exercise:

• object/iterator_prototypes.rs — attach_iterator_prototype/chain_to switched off object_set_static_prototype so OBJECT_META_FLAG_PROTO_OVERRIDE is no longer set on array/Map/Set/String iterator prototypes
• object/field_get_set/prototype_override.rs (new), get_field_by_name_tail.rs
• object/native_call_method.rs, object/class_registry.rs

The gen().map(...) failure is consistent with a built-in iterator prototype no longer being reachable by the lookup path that resolves helper methods.

Acceptance criteria

• All four tests pass, and A prototype method replaced after class registration is not seen by newly constructed instances #9239's own regression (issue_9131_prototype_method_replacement) still passes.
• gap-suite shards actually RUN and are green before merge — a cancelled gap-suite-build must not be read as a pass.