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REIFY Phase 1.1 (Phase 1 complete). instantiateTypeFunction detects a type-fn body that returns reify(...) (findReturnReifyCall) and routes it to reifyType under the instantiation's name — mangled for inline use, the alias name for `Foo :: Box(i64)` — with the type-arg bindings active so reify payloads (`payload = T`) resolve against the instantiation args. Placed before the general case, whose resolveTypeWithBindings would route the reify call to the inline-position loud bail. Registering under the mangled name lets the top-of-instantiation cache return the SAME TypeId on a second instantiation, so Box(i64) resolved at two independent sites is ONE type (Contract 1). examples/0615 green (build()->consume() cross-site + `b : Box(i64) = .none`). Suite green (671 examples, 447 unit).
115 lines
6.9 KiB
Markdown
115 lines
6.9 KiB
Markdown
# CHECKPOINT-REIFY — comptime `type_info` / `reify` (async-first foundation, step 3)
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Companion to [PLAN-REIFY.md](PLAN-REIFY.md). Update after every step (one step at a
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time, per the cadence rule).
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## Last completed step
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**Phase 1 (type-fn → reify identity) — COMPLETE.** A type-fn body that returns
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`reify(...)` now mints the enum under the instantiation's name:
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`instantiateTypeFunction` (`lower/generic.zig`) detects a reify-returning body
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(`findReturnReifyCall`) and routes it to `reifyType(<mangled-or-alias name>,
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reify_call)` with the type-arg bindings active (so `payload = T` resolves to the
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bound arg) — placed BEFORE the general case, which would otherwise route the
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reify call to the inline-position loud bail. Registering under the mangled name
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lets the fn's top-of-instantiation cache return the SAME `TypeId` on the second
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instantiation → `Box(i64)` at two independent sites is ONE type (**Contract 1**).
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`examples/0615` green (`build()`→`consume()` cross-site, plus `b : Box(i64) =
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.none`); full suite green (671 examples, 447 unit). Cadence: 1.0 xfail (empty
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marker, RED) → 1.1 green (this commit).
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### (prior) Phase 0.2 (green) — Phase 0 COMPLETE. Implemented `reify(.enum(...))`:
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`Lowering.reifyType` (in `lower/nominal.zig`) reads the flat-enum `TypeInfo`
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literal off the AST, synthesizes an `ast.EnumDecl`, and feeds it through the
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SAME `type_bridge.buildEnumInfo` path source enums use → the minted type is
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byte-identical to a hand-written `enum { value: i64; closed; }` and flows
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through enum codegen unmodified (**Contract 2 confirmed** — a source enum
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exhibits the exact same construct/match behavior, verified by probe). Wired at
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the `E :: reify(...)` const-decl hook in `lower/decl.zig`. `examples/0614`
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green (`value 3` / `closed`, exit 0); snapshots captured; full suite green
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(670 examples, 447 unit). Unsupported reify shapes bail loudly via
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`reifyBail` (never a silent default).
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Also landed (user-directed, separate commit `feat(parser):`): reserved keyword
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as a member name after `.` (`.enum`, `case .enum:`, `x.enum`) — so the reify
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example reads `reify(.enum(...))` without a backtick. readme updated.
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### Two earlier Phase-0 commits
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- **0.1 (xfail).** Added `examples/0614` + empty `.exit` marker → RED.
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- **0.0 (lock).** Added the comptime type-metaprogramming surface as the
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on-demand module `library/modules/std/meta.sx` (NOT the prelude — see decision
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below): `EnumVariant`/`EnumInfo`/`TypeInfo` data types + bodyless `#builtin`
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decls `reify` / `type_info` / `field_type`. Each builtin bails LOUDLY when
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reached unimplemented (no silent default). Unit test `src/parser.test.zig`
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(registered in `src/root.zig`) locks that the decls parse. `zig build test`
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green (447/447 unit, 669/669 examples).
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## Current state
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- `modules/std/meta.sx` declares the surface; the variant uses the backtick raw
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escape `` `enum `` (reads as the keyword, not a mangled `enum_`).
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- **Loud bails wired (unimplemented → diagnostic, never a silent type):**
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- `reify(...)` in a `::` type-alias position → `decl.zig` (the `.call`
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const-decl branch) emits "reify is not yet implemented (REIFY Phase 0.2)"
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and poisons the alias to `.unresolved`. This is also where Phase 0.2 will
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hook the real construction.
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- `reify` / `field_type` in any other type position →
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`generic.zig:resolveTypeCallWithBindings` (defense-in-depth).
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- `type_info(...)` in expression position →
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`call.zig:tryLowerReflectionCall`.
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- No interpreter-side construction yet — `reify` mints nothing.
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## Decision (0.0)
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**Meta lives in `modules/std/meta.sx`, not the prelude (`core.sx`).** Declaring
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the data types in the always-loaded prelude interns them into every module's
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type table and shifts every `.ir` snapshot (broke 37 examples in a trial). An
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on-demand import keeps the prelude clean; reify users `#import
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"modules/std/meta.sx"`. (User-directed.)
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## Next step
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**Phase 2 (`type_info` + `field_type`).** Reflect a struct/tuple → read variant /
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field names + **types** (`field_type($T, i) -> Type`, `type_info($T) -> TypeInfo`).
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xfail → green by implementing both over the type table (reuse the
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`field_count`/`field_name` reflection path; both currently bail loudly —
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`type_info` in `call.zig:tryLowerReflectionCall`, `field_type` in
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`generic.zig:resolveTypeCallWithBindings`). NOTE: `reifyType` still reads a LITERAL
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`TypeInfo` off the AST (works for the inline-literal and type-fn-over-literal cases
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Phases 0–1 use); a `type_info`-derived (computed, non-literal) `TypeInfo` fed back
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into `reify` would need the reader generalized (or interp evaluation) — call that out
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when Phase 2 enables round-tripping.
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SELF-REFERENCE = Phase 4, API DECIDED (user-directed): explicit **`declare()` →
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`define(h, info)`** (the declaration-vs-definition split; NOT a `reify_rec((self)=>…)`
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closure). `declare()` returns a forward nominal `Type` handle (named from the `::`
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LHS) usable freely in any later `TypeInfo` — `*List`, `[]List`, and across types for
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MUTUAL recursion the one-`self` closure couldn't express; `define(handle, info)` fills
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the body. `reify(info)` stays as the one-shot sugar. Maps onto existing machinery:
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declare = empty nominal slot (`reserveShadowEnumSlot`-style), define = `buildEnumInfo`
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+ `updatePreservingKey`, struct-stub→tagged_union re-key already handled
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(`internNamedTypeDecl`'s `adoptsForwardStructStub`). Loud invariants: never-defined
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declare = hard error; by-value self-inclusion rejected (infinite size). Full write-up
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in PLAN-REIFY Phase 4.
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## Known issues
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None yet.
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## Log
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- **1.1 (green) — Phase 1 done.** Type-fn body `return reify(...)` routes through
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`reifyType` under the instantiation name (`findReturnReifyCall` +
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mangled-name registration); `Box(i64)` at two sites = one type (Contract 1);
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`0615` green.
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- **1.0 (xfail).** `0615` + empty `.exit` marker → RED (reify bailed in type-fn body).
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- **0.2 (green) — Phase 0 done.** `reifyType` mints a flat enum from a literal
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`TypeInfo` via the shared `buildEnumInfo` path; `0614` green; Contract 2 confirmed
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(reify'd enum == source enum, same construct/match). Payload-less variant idiom in
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the example is `c : E = .closed;` (enum-literal target), same as a source enum.
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- **parser (user-directed).** Keyword as member name after `.` — see `feat(parser)`.
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- **0.1 (xfail).** `0614` + empty `.exit` marker → RED.
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- **0.0 (lock).** Meta surface in `modules/std/meta.sx` (data types + 3 bodyless
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`#builtin` decls), loud bails at all three reach points, `src/parser.test.zig`
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parse-lock. Two user-directed refinements folded in: variant uses `` `enum ``
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raw escape; surface moved out of the prelude into its own module to avoid
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type-table / `.ir`-snapshot churn. `zig build test` green.
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- **Stream carved.** Selected as the first async-first foundation: `reify` gates both
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channel result types (`RecvResult($T)`) and `race`'s synthesized union, is fully
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validated (3 reviewers), and is a self-contained compiler/type-system feature
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testable in isolation (`06xx` comptime). Generic-enum syntax dropped in its favor.
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