ffi M5.A.next: checkpoint — pack feature step 1 done (1c.A → 1d.B)
Logs the four commits that closed out step 1 of the variadic heterogeneous type packs feature: - 1c.A: parser-rejection lock-in for `..$args` inside `Closure(...)`. - 1c.B: parser + AST + types.zig `pack_start` representation. - 1d.A: impl-matching concrete-only miss lock-in. - 1d.B: pack-aware impl matching with $args + $R binding through `param_impl_pack_map` and `pack_bindings`. Next step is plan step 2 — runtime `args[$i]` indexing + per-mono mangling — opening the door to body-side pack reflection that step 5 needs to retire the hand-rolled `Into(Block)` impls. Also catches up the 1b entry which the prior session left uncommitted in the working tree.
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@@ -6,8 +6,148 @@ add a test and make it pass — that's two commits).
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## Last completed step
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**M5.A.next.1d.B — variadic heterogeneous type packs: pack-aware impl
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matching** (commit `08feb60`).
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Pack-shaped impls (`impl P(...) for Closure(..$args) -> $R`) now
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match concrete closure sources at xx resolution time. Concrete
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impls retain priority — pack matching only fires when
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`param_impl_map` misses on the concrete key.
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New plumbing in [src/ir/lower.zig](../src/ir/lower.zig):
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- `PackParamImplEntry` carries the pack-shaped source TypeId plus
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the pack-var and ret-var names extracted from the impl AST's
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`target_type_expr`. `registerParamImpl` detects pack-shaped
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sources via `pack_start != null` on the resolved closure type
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and additionally registers in a new `param_impl_pack_map`
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keyed by `"Proto\x00<arg_mangled>"` (no source suffix).
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- `tryUserConversion` re-shapes the lookup so the pack path runs
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on miss. `tryPackImplMatch` walks the pack entries, verifies
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the source's fixed prefix matches the impl's prefix, binds
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the pack-var to the source's tail param TypeIds, binds the
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ret-var (when the impl's return is generic) to the source
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return, and monomorphises the convert method. Mangled name
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stays keyed on the concrete source so distinct call shapes
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monomorphise separately.
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- `pack_bindings: ?StringHashMap([]const TypeId)` is saved /
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restored around monomorphisation, mirroring `type_bindings`.
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- `resolveClosureTypeWithBindings` handles the `closure_type_expr`
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node during type resolution: when the closure carries a
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`pack_name` AND `pack_bindings` has a binding for it, the
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bound TypeIds are appended after the fixed prefix and the
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result is a concrete (non-pack) closure type — so the impl
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body's `self: Closure(..$args) -> $R` substitutes to the
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concrete source closure during monomorphisation.
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`examples/155-pack-impl-match.sx` flips from the
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"no Into(Block) for cl_s32_bool__bool" lock-in diagnostic to
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"pack impl match ok": one user-declared
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`impl Into(Block) for Closure(..$args) -> $R` covers a
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`Closure(s32, bool) -> bool` source that stdlib has no
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hand-rolled impl for. The constructed Block isn't invoked
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(invoke=null) — the test exercises matching + monomorphisation,
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not the trampoline (step 5 of the plan).
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Same-file duplicate pack impls diagnose at registration;
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cross-module pack-impl visibility and multi-pack-impl
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specificity are deferred (matching the concrete path's existing
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TODOs).
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193/193 example tests + `zig build test` green. Step 1 of the
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pack-feature plan ("Parser + type rep + impl matching") is now
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done.
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**Next step** — Step 2 of the plan: runtime indexing
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(`args[$i]`) lowers to positional access; per-mono mangling
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extends with a stable pack-shape hash. Builder fns receive
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`$args` (a comptime `[]Type`) as a regular value parameter.
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Replaces a hand-rolled Into impl in stdlib once step 2 + step
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3 (type-reflection intrinsics) land.
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---
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**M5.A.next.1d.A — pack impl matching: lock in concrete-only miss**
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(commit `ce3c2fe`).
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Pinned today's matching behaviour ahead of 1d.B. A user-declared
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`impl Into(Block) for Closure(..$args) -> $R` registers under a
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pack-shaped source key in `param_impl_map`; the xx site mangles
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the concrete `Closure(s32, bool) -> bool` source and finds
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nothing → the existing focused diagnostic fires ("no `Into(Block)
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for cl_s32_bool__bool` impl — add a per-signature
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`__block_invoke_<sig>` trampoline + Into impl..."). The pack impl
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is reachable in the file but never considered.
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`examples/155-pack-impl-match.sx` captures the rejection at line
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43 column 21 (the `xx cl : *Block` site). 193/193 example tests
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+ `zig build test` green.
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---
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**M5.A.next.1c.B — pack type rep: Closure(..$args) parses + interns**
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(commit `6582449`).
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`parseTypeExpr`'s `Closure(...)` arm now accepts a trailing
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`..$name` (sigil optional) as a variadic-pack marker. Pack must
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be terminal — `)` is the only token accepted after the name.
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`ClosureTypeExpr` AST gains `pack_name: ?[]const u8` carrying
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the identifier so later slices can name the binding.
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`FunctionInfo` / `ClosureInfo` in `src/ir/types.zig` grow a
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`pack_start: ?u32 = null` field. `Closure(..$args) -> R` interns
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as `params = []`, `pack_start = Some(0)` — distinct from any
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concrete `Closure(...) -> R` shape thanks to updated hash/eql
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arms. New constructor pair `closureTypePack` /
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`functionTypePack` keeps the existing single-shape constructors
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unchanged.
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`type_bridge.resolveClosureType` calls `closureTypePack` when
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`pack_name != null`. The pack starts after the fixed prefix,
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so `Closure(Prefix, ..$args)` resolves with `params = [Prefix]`,
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`pack_start = Some(1)`.
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`examples/154-pack-type-rep.sx` flips from rejecting-with-error
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to positive parse smoke. 192/192 example tests + `zig build
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test` green.
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---
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**M5.A.next.1c.A — pack type rep: lock in parser rejection**
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(commit `bb6eca6`).
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Locked in today's `parseTypeExpr` Closure-arm rejection of `..$args`.
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`examples/154-pack-type-rep.sx` uses `..$args` inside a
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`Closure(...)` type expression — the pack-shape spelling used by
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impl headers like `impl Into(Block) for Closure(..$args) -> $R`.
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Today's parser recognized `..$args` only at parameter-list sites
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(1b); the Closure type arm called `parseTypeExpr` per position
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and hit "expected type name" at line 18 column 26.
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---
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**M5.A.next.1b — variadic heterogeneous type packs: parser accepts
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`..$args`** (commit `a51fe26`).
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`parseParams()` in `src/parser.zig:1558` accepts a leading `..`
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before the optional `$` sigil and the parameter name. The old
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`args: ..T` form (variadic marker after the colon) still works —
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both paths set the same `is_variadic` flag. A pack declaration
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`..$args` parses as:
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- `is_variadic = true` (leading `..`)
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- `is_comptime = true` (the `$` sigil)
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- `type_expr = inferred_type` (no `:` annotation)
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`examples/150-pack-parse.sx` flipped from rejecting-with-error to
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positive parse smoke. The no-colon branch of `parseParams`
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propagates `is_variadic` and `is_comptime` onto the Param
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struct, so later slices can read both flags from the parsed AST.
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191/191 example tests + `zig build test` green.
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---
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**M5.A.next.1a — variadic heterogeneous type packs: parse lockin**
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(this commit).
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(`ad82847`).
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First slice of the `..$args` (variadic heterogeneous type pack)
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feature per the plan saved at
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