GC-ness now comes from the inference pass, not only the annotation. A class is
traced if the structural SCC put it in `syms.traced`, OR (temporary bridge
until demand-promotion lands) it still carries `@gc`.
- Types.symbols gains a `traced : StringSet.t`; is_gc_class reads it (union'd
with the surviving @gc annotation). All symbols literals + both merges carry
the field.
- typecheck_all injects the classification once (Gcinfer.classify -> traced)
into the merged table AND every module table, before typecheck/owner/emit.
- emit.ml routes the class gc-flag and the union/drop decision through
is_gc_class instead of the raw `.is_gc`, so structurally-inferred gc classes
get the runtime flag. Field-kind derivation already routed through is_gc_class.
- gcinfer.traced_names exposes the traced set for injection.
Effect: docs/examples/gc-cycle now COMPILES with no annotation (the WO-E301
use-after-move at the ring-closing store is gone) — traced classes alias
freely. Bytecode is byte-identical to writing `@gc class Node`.
Verified: woc-test 566/0 (goldens unchanged — every current @gc class stays gc
via the annotation branch, and no golden has a structural-gc-non-annotated
class); oop-e2e 79/0 (gc corpus green).
Not in this slice: demand-promotion (the acyclic-aliased PriceCache case still
needs the @gc bridge) and @gc-in-source-as-error (Phase 2b); the ring RUNNING
(the RC runtime doesn't implement nullable-gcref `?Node` fields — Phase 3).
WO-W201 still fires on gc-cycle (retired in Phase 4).
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Design-first deliverable for iteration 7b (no runtime/compiler code yet).
docs/examples/gc-cycle explains, by example, how pointers flow through the heap
and the collector's mark-sweep logic:
- types.wo: Node (self-referential ?Node -> inferred `gc`/traced) vs Segment
(acyclic -> `owned`, deterministically dropped)
- main.wo: ring_demo builds a->b->c->a and abandons it; owned_demo shows the
drop path with no collector
- README.md: the model (ownership frees the 99%, tracing only the cyclic/
aliased residue, inference decides), the 16-byte header rewrite (retire
rc+borrow -> 8-byte sweep-list link, colors in flag bits), where a traced
pointer lives (root via pc gc-mask / GCREF field / container), and the
tri-color incremental algorithm with the Yuasa deletion barrier. Two mermaid
step diagrams (heap+roots, collector cycle) + the owned contrast.
Grounded in the approved spec (2026-08-11-inferred-gc-mark-sweep-design.md) and
the real runtime structures (obj.h/wob.h: wo_hdr, WO_K_GCREF, arena, wo_obj_size).
Run status: honest — the sample does NOT build today; woc reports WO-E301
(use-after-move at the ring-closing store), which is exactly the aliasing that
"traced classes alias freely" unblocks under 7b. README records this.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
