language/runtime: align global object, declaration instantiation, and var hoisting semantics

[andrewtdiz]

Summary

Global this, duplicate function declarations, global property updates, and var hoisting initialize and mutate values according to ECMAScript.

Affected Test262 rows

• Web Streams API: implement ReadableStream + blob.stream() / response.body #237 language/global-code/S10.1.7_A1_T1.js (runtime-fail: Uncaught exception: Support custom menu bar items #1: The this value associated with an executioncontext is immutable. Actual: this was deleted)
• fix(fetch): #234 real Blob with arrayBuffer/text/bytes/slice instance methods #238 language/global-code/decl-func-dup.js (compile-fail: Error compiling module 'case.js' (case.js) with --backend llvm: clang -c failed (status=exit status: 1).)
• fix(async): #256 spec-compliant microtask ordering for plain async functions #262 language/punctuators/S7.7_A1.js (runtime-fail: TypeError: Cannot read properties of undefined (reading 'nan'))
• feat(ui): Phase 2 v3.3 — iOS toast + setText #327 language/types/boolean/S8.3_A1_T1.js (runtime-fail: Uncaught exception: #0 x !== undefined, but actual is 0)

Perry actual behavior from report

• 1 x compile-fail: Error compiling module 'case.js' (case.js) with --backend llvm: clang -c failed (status=exit status: 1).
• 1 x runtime-fail: TypeError: Cannot read properties of undefined (reading 'nan')
• 1 x runtime-fail: Uncaught exception: #0 x !== undefined, but actual is 0
• 1 x runtime-fail: Uncaught exception: Support custom menu bar items #1: The this value associated with an executioncontext is immutable. Actual: this was deleted

Node / ECMAScript expected behavior

Global this, duplicate function declarations, global property updates, and var hoisting initialize and mutate values according to ECMAScript.

Likely subsystem

global environment record / codegen globals / unary/update expression lowering

Acceptance criteria

• delete this and global this.nan update rows match Node/Test262.
• Duplicate global function declarations leave the last declaration callable.
• var declarations are hoisted to undefined, not initialized as numeric zero.

Validation

Run the Test262 differential against the affected area and confirm these rows leave the gap report:

scripts/test262_subset.py --root vendor/test262 --dir language/global-code language/punctuators language/types/boolean --sample-cap 99999 --report /tmp/SCOPE_GLOBALS.json

This is Perry language/runtime semantics triage, not a Node core API compatibility issue.

[andrewtdiz]

Validated this against current origin/main (c4ba7a765) and the issue appears stale-open now.

Checks run on 2026-06-03 UTC:

• Script-style Node oracle via npm exec --yes --package=node@26 -- node < tmp_probe_3575_script.ts
• Perry via PERRY_NO_AUTO_OPTIMIZE=1 PERRY_ALLOW_UNIMPLEMENTED=1 target/release/perry tmp_probe_3575_script.ts -o /tmp/perry_probe_3575_script && /tmp/perry_probe_3575_script
• Existing regression: test-files/test_issue_3585_bindings.ts under both Node 26 and Perry

The focused probe covered the acceptance criteria here: duplicate function declarations resolve to the last body, var reads before initialization are undefined, delete this returns true without removing the global this, and this.nan assignment/update remains NaN. Node and Perry produced matching output. The existing test_issue_3585_bindings.ts regression also passes and covers the related binding/globalThis behavior.

I do not have permission to close the issue, but I would treat this one as resolved on current main.