fix(runtime): promise reactions must not clobber the single handler slot (combinators + .finally)

CHANGELOG.md

@@ -1,3 +1,7 @@
+## v0.5.1216 — promise reactions must not clobber the single handler slot (#5867)
+
+A promise carries one inline reaction slot (`on_fulfilled`/`on_rejected`/`next`); `js_promise_then` diverted 2nd+ reactions to the overflow table, but two other attach paths stored unconditionally: `js_promise_attach_handlers` (Promise.all/allSettled/race/any via `promise_resolve_for_combinator`, stream adapters) destroyed any earlier reaction — `p.then(cb); Promise.all([p])` lost `cb`, and two combinators sharing one pending input destroyed each other's forwarder so the loser's remaining-count never reached zero (permanent hang; the shared webpack/Turbopack chunk-promise shape, #5437 family) — and `js_promise_finally` on a PENDING promise overwrote the slot and nulled `promise.next`. All three occupancy checks (including `js_promise_then` itself) now treat a non-null `next` as occupied too: a degenerate no-arg `p.then()` parks with both closures null and only `next` set, and the spec combinators attach per-element reactions through `js_promise_then` via `invoke_then`, so `const c = p.then(); Promise.all([p])` stranded `c`'s chain. Also carries the #5437-branch fix: `.finally()` on a SETTLED promise dispatches its own wrapper exactly once via `Task::Inline` (previously N settled finallys ran the last wrapper N times — Turbopack `loadChunkAsync` / Next.js CacheSignal), and settled `.finally` now captures the attach-time async context. e2e: `crates/perry/tests/promise_reaction_slot_overflow.rs` (7 scenarios byte-for-byte vs `node --experimental-strip-types`). `promise/then.rs` (2008 lines) is allowlisted 8-over the file-size gate; the topical split of its #1545 value-read-thunk tail is a tracked follow-up.
+
 ## v0.5.1215 — boxing analysis descends into labeled blocks (#5871)
 
 Five walkers in perry-codegen's `boxed_vars.rs` had no `Stmt::Labeled` arm (while `collect_write_ids_in_stmt` did), so a captured variable reassigned — or captured — inside a labeled block was never boxed: closures kept a creation-time snapshot and never observed later writes. Signature: a captured array read `.length === 0` through the closure while `JSON.stringify` in the same scope printed all four elements — previously seen only inside large minified webpack bundles, which emit labeled early-exit blocks (`e: { … break e; }`) pervasively (#5869). Adds the `Stmt::Labeled { body, .. }` recursion arm to `collect_self_recursive_closure_ids`, `collect_for_init_ids`, `collect_closure_refs_and_writes_in_stmt`, `collect_outer_writes_in_stmt`, and `collect_let_types_in_stmts`. The closure-created-INSIDE-the-label variant remains open on #5869 (perry-hir lowers it with `mutable_captures: []` under the `Labeled{DoWhile(false)}` wrapper); its regression test ships `#[ignore]`d in `crates/perry/tests/issue_5869_labeled_block_capture_boxing.rs`.

CLAUDE.md

@@ -8,7 +8,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 Perry is a native TypeScript compiler written in Rust that compiles TypeScript source code directly to native executables. It uses SWC for TypeScript parsing and LLVM for code generation.
 
-**Current Version:** 0.5.1215
+**Current Version:** 0.5.1216
 
 
 ## TypeScript Parity Status