fix eval delete bindings

[Monti-27]

Fixes #5333.

Direct eval-created local var and function bindings were not treated as deletable at runtime, so delete left them visible and later var initialization could recreate them.

This tracks deleted eval-created local bindings in function environments and avoids recreating them after deletion.

Tests:

• cargo test -p boa_engine env -- --nocapture
• cargo test -p boa_engine unary_delete -- --nocapture
• cargo clippy -p boa_engine --all-features --all-targets -- -D warnings
• cargo make run-ci

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	53,125	53,125	0
Passed	51,051	51,071	+20
Ignored	1,482	1,482	0
Failed	592	572	-20
Panics	0	0	0
Conformance	96.10%	96.13%	+0.04%

Fixed tests (20):

test/staging/sm/Function/function-name-assignment.js (previously Failed)
test/staging/sm/strict/15.4.4.8.js (previously Failed)
test/staging/sm/strict/15.5.5.1.js (previously Failed)
test/staging/sm/strict/8.12.5.js (previously Failed)
test/staging/sm/strict/15.4.4.13.js (previously Failed)
test/staging/sm/strict/8.12.7.js (previously Failed)
test/staging/sm/strict/15.4.4.9.js (previously Failed)
test/staging/sm/strict/15.10.7.js (previously Failed)
test/staging/sm/strict/15.4.4.12.js (previously Failed)
test/staging/sm/async-functions/await-in-arrow-parameters.js (previously Failed)
test/staging/sm/async-functions/await-in-parameters-of-async-func.js (previously Failed)
test/staging/sm/expressions/nested-delete-name-in-evalcode.js (previously Failed)
test/staging/sm/expressions/destructuring-array-default-yield.js (previously Failed)
test/staging/sm/expressions/short-circuit-compound-assignment.js (previously Failed)
test/staging/sm/eval/exhaustive-fun-normalcaller-direct-normalcode.js (previously Failed)
test/staging/sm/PrivateName/lexical-presence.js (previously Failed)
test/staging/sm/extensions/for-loop-with-lexical-declaration-and-nested-function-statement.js (previously Failed)
test/staging/sm/extensions/nested-delete-name-in-evalcode.js (previously Failed)
test/language/eval-code/direct/var-env-func-init-local-new-delete.js (previously Failed)
test/language/eval-code/direct/var-env-var-init-local-new-delete.js (previously Failed)

Tested main commit: 3ce87f0fa03c5c037fb667f7f21a4996abbbc714
Tested PR commit: 15de044293e4c8f94052331b448e0f68356a4c7f
Compare commits: 3ce87f0...15de044

[codecov]

Codecov Report

❌ Patch coverage is 90.24390% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.05%. Comparing base (6ddc2b4) to head (15de044).
⚠️ Report is 965 commits behind head on main.

Files with missing lines	Patch %	Lines
core/engine/src/bytecompiler/mod.rs	40.00%	3 Missing ⚠️
core/engine/src/environments/runtime/mod.rs	90.32%	3 Missing ⚠️
core/engine/src/vm/code_block.rs	0.00%	3 Missing ⚠️
...e/src/environments/runtime/declarative/function.rs	94.59%	2 Missing ⚠️
...engine/src/environments/runtime/declarative/mod.rs	94.44%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #5344       +/-   ##
===========================================
+ Coverage   47.24%   60.05%   +12.81%     
===========================================
  Files         476      566       +90     
  Lines       46892    63024    +16132     
===========================================
+ Hits        22154    37851    +15697     
- Misses      24738    25173      +435     

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[zhuzhu81998]

i am not familiar with this part of the codebase, but this feels, kinda hacky?

are you sure this is not something that happens because of incompliance with spec somewhere?

[Monti-27]

i am not familiar with this part of the codebase, but this feels, kinda hacky?

are you sure this is not something that happens because of incompliance with spec somewhere?

Yeah, fair point. the current approach is not clean enough. The Test262 report also caught a regression around eval("var x=delete(x)") so I’ll rework this instead of trying to patch around it

[hansl]

Let us know when this is ready to review, or close it and re-open a new PR :)

[Monti-27]

this new changes moves deletability into the function environment itself, marks newly extended eval bindings as deletable, and re resolves stale deleted locators before assignment. this matches the EvalDeclarationInstantiation / CreateMutableBinding(name, true) behavior more directly

[Monti-27]

Updated this now. The fix keeps deleted eval-created bindings in the function environment and uses a separate eval declaration var path, so normal var statements do not recreate deleted bindings.

Tests:

• cargo test -p boa_engine tests::env --lib
• cargo clippy -p boa_engine -- -D warnings
• cargo make run-ci from the pre-push hook
• targeted Test262 eval delete cases

[Monti-27]

@hansl its ready for review !!