Pack-shaped impls (`impl P(...) for Closure(..$args) -> $R`) now
match concrete closure sources at xx resolution time. Concrete
impls keep their priority — pack matching only fires on a
concrete-key miss in `param_impl_map`.
New plumbing in src/ir/lower.zig:
- `PackParamImplEntry` carries the pack-shaped source TypeId plus
the pack-var and ret-var names extracted from the impl AST's
`target_type_expr`. `registerParamImpl` detects pack-shaped
sources via `pack_start != null` on the resolved closure type
and additionally registers in a new `param_impl_pack_map`
keyed by `"Proto\x00<arg_mangled>"` (no source suffix).
- `tryUserConversion` re-shapes the concrete lookup so the pack
path runs on miss. `tryPackImplMatch` walks the pack entries,
verifies the source's fixed prefix matches the impl's prefix,
binds the pack-var to the source's tail param TypeIds, binds
the ret-var (when the impl's return is generic) to the source
return, and monomorphises the convert method. Mangled name
stays keyed on the concrete source so distinct call shapes
monomorphise separately.
- `pack_bindings: ?StringHashMap([]const TypeId)` is saved/
restored around monomorphisation, mirroring `type_bindings`.
- `resolveClosureTypeWithBindings` handles the closure_type_expr
node during type resolution: when the closure carries a
`pack_name` AND `pack_bindings` has a binding for it, the
bound TypeIds are appended after the fixed prefix and the
result is a concrete (non-pack) closure type — so the impl
body's `self: Closure(..$args) -> $R` substitutes to the
concrete source closure during monomorphisation. Without an
active binding, the pack shape is preserved.
`examples/155-pack-impl-match.sx` flips from the
"no Into(Block) for cl_s32_bool__bool" lock-in diagnostic to
"pack impl match ok": one user-declared
`impl Into(Block) for Closure(..$args) -> $R` covers a
`Closure(s32, bool) -> bool` source that stdlib has no
hand-rolled impl for. Constructed Block isn't invoked
(invoke=null) — the test exercises only the matching +
monomorphisation, not the trampoline (step 5 of the plan).
Existing concrete-impl paths unchanged: 95-objc-block-noop,
96-objc-block-multi-arg, and stdlib's hand-rolled
`Into(Block) for Closure(bool) -> void` continue to pass through
the concrete map first. Same-file duplicate pack impls
diagnose at registration; cross-module visibility and
multi-pack-impl specificity stay TODOs (matching the deferred
Phase 5 work on the concrete path).
193/193 example tests + `zig build test` green.
Step 1d lock-in test pinning today's matching behaviour.
`registerParamImpl` records every impl in `param_impl_map` keyed
by `"Proto\x00<arg_mangled>\x00<src_mangled>"`. For a pack impl
`Into(Block) for Closure(..$args) -> $R` the key contains the
pack-shaped closure's mangle (interns with `pack_start = Some(0)`
after 1c.B). At the `xx cl : *Block` site the lookup mangles the
concrete `Closure(s32, bool) -> bool` source and finds nothing —
the existing focused diagnostic fires:
no `Into(Block) for cl_s32_bool__bool` impl — add a per-signature
`__block_invoke_<sig>` trampoline + Into impl alongside the
existing ones in modules/std/objc_block.sx, or declare it in
your own code
The pack impl is reachable in the file but never considered.
Next commit (1d.B):
- New `param_impl_pack_map` keyed by `"Proto\x00<arg_mangled>"`
(no src) — populated by `registerParamImpl` when the source
is pack-shaped.
- `tryUserConversion` walks the pack map on concrete-key miss.
Pack shape matches when the impl's fixed prefix equals the
source's matching prefix; the remainder binds to `$args` and
the source's return type binds to `$R`. Concrete impls win
over pack impls (specificity).
- `resolveTypeWithBindings` learns the closure_type_expr path
so the impl body's `self: Closure(..$args) -> $R` substitutes
to the concrete source closure during monomorphisation.
The `Closure(s32, bool) -> bool` shape is not covered by stdlib
or 96-block-multi-arg's hand-rolled impls, so the pack impl is
the only candidate post-1d.B.
193/193 example tests + `zig build test` green.
