From 6dcb620b48ef73cb3f46d91d863fa5fbed1a35ef Mon Sep 17 00:00:00 2001
From: agra <alex@swipelab.co>
Date: Fri, 26 Jun 2026 13:41:42 +0300
Subject: [PATCH] =?UTF-8?q?docs:=20PLAN-RACE=20=E2=80=94=20composition=20g?=
 =?UTF-8?q?ap=20fixed,=20synthesis=20proven;=20next=20is=20the=20race=20ru?=
 =?UTF-8?q?ntime=20in=20sched.sx?=
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Content-Type: text/plain; charset=UTF-8
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---
 current/PLAN-RACE.md | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/current/PLAN-RACE.md b/current/PLAN-RACE.md
index 100d4b8e..5471ce28 100644
--- a/current/PLAN-RACE.md
+++ b/current/PLAN-RACE.md
@@ -75,14 +75,19 @@ Prereqs DONE (each committed + adversarially reviewed + suite-green):
   `($T) -> Type` builder can `inline for 0..field_count(T)` and size `[field_count(T)]EnumVariant`.
   Verified: the variable-arity loop + array dim now work inside `RaceResult`.
 
-**NEXT BLOCKER (step 2, not yet resolved): nested comptime-type-call composition.** Building each
-variant payload needs `*Task(A) → A`, i.e. `field_type(pointee(field_type(T, i)), 0)`. Today:
-- passing a `field_type(...)` RESULT as the type-arg to a generic (`TaskResult(field_type(T, i))`) →
-  *"cannot infer generic type parameter 'P'"*;
-- the same nested inline (`field_type(pointee(field_type(T, i)), 0)`) → *"cannot infer 'T' for
-  field_type"*;
-- a `::` alias bound to a comptime-type-call result (`P0 :: field_type(NT, 0)`) → *"unresolved type
-  'P0'"* (kin to issue 0196).
-So a comptime-type-call's Type result isn't usable as a generic type-arg / `::` alias / nested
-type-call arg. This composition gap is the next thing to fix (or design around) before the variable-
-arity `RaceResult` payloads can be built. Everything up to the payload projection works.
+- **comptime type-call composition** fixed (`eb18bbc6`) — a `field_type(...)`/`pointee(...)` result is
+  now usable as a `Type`-typed struct-field value, a generic `$P: Type` arg, and a nested type-call
+  arg (incl. with an `inline for` loop-var index). The **variable-arity `RaceResult` synthesis works
+  end-to-end** (proven by `examples/comptime/0649-comptime-typecall-composition.sx`: reflect a named
+  tuple of `*Box(..)` handles → mint a tagged-union with the tuple's labels, projecting `*Box(A)`→`A`).
+
+**All comptime prerequisites are now in place — the rest is pure-sx library work in sched.sx.**
+
+**NEXT (step 2–4): the actual `race` in `library/modules/std/sched.sx`.**
+- `RaceResult :: ($T) -> Type` over `*Task(..)` (the 0649 shape, with `Task` instead of `Box`).
+- `race :: ufcs (self: *Scheduler, tasks: $T) -> RaceResult(T)`: suspend the caller until the FIRST
+  task is `.ready`; build the winner variant (construct the minted union by the winning index/label —
+  watch for a possible variant-construction-by-dynamic-index gap); then `cancel` + `wait`-join every
+  loser before returning (structured). Reuses `suspend_self`/`wake` + `Task.cancel`/`wait`.
+- Lock with a 2/3-task example (deterministic winner via `sleep` ordering, asserting losers cancelled).
+- Validate byte-identical on aarch64-macOS host AND aarch64-linux container; full `zig build test`.