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fix(0126): array args bind []$T generic params; uninferrable type params diagnose at the call

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extractTypeParam's slice arm only extracted from slice-typed args, so
first(a) with a : [3]s64 at first :: (xs: []$T) -> T left T unbound
and the mono body reached LLVM emission carrying the .unresolved
sentinel (panic). The arm now also extracts from array args via the
array's element type — mirroring the array→slice promotion concrete
slice params already perform; the existing arg coercion handles the
rest.

lowerGenericCall additionally diagnoses any still-uninferrable TYPE
param at the call site instead of monomorphizing unbound — the
deliberate string-at-[]$T gap used to hit the same sentinel panic and
now errors with a source-located message. Comptime value params
($N: u32) and ..$Ts packs bind through their own dispatch and stay
exempt.

Regressions: examples/0212-generics-array-arg-slice-param.sx (scalar /
u8 / struct elements + the slice spelling) and
examples/1168-diagnostics-generic-param-uninferrable.sx (string arg
diagnostic) — both failed pre-fix.
This commit is contained in:
agra
2026-06-12 08:31:45 +03:00
parent b625b74046
commit 309f48e1b5
11 changed files with 118 additions and 2 deletions
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21
issues/0126-array-arg-slice-generic-param-unbound.md
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@@ -1,4 +1,23 @@
# 0126 — array arg at a `[]$T` param leaves T unbound → LLVM emission panic
# RESOLVED — 0126: array arg at a `[]$T` param leaves T unbound → LLVM emission panic
> **RESOLVED** (2026-06-12). Root cause: `extractTypeParam`'s
> `.slice_type_expr` arm (src/ir/lower/generic.zig) only extracted from
> `.slice`-typed args, so an array arg left `T` unbound and
> `monomorphizeFunction` stamped `.unresolved` through the body — no
> diagnostic before the emitter's sentinel panic. Fix: (1) the arm also
> extracts from `.array` args via the array's element type, mirroring
> the array→slice promotion concrete slice params perform (the existing
> coercion then handles the lowered arg); (2) `lowerGenericCall`
> (src/ir/lower/call.zig) diagnoses any still-uninferrable TYPE param
> at the call site ("cannot infer generic type parameter ...") instead
> of monomorphizing unbound — covers the deliberate string-at-`[]$T`
> gap, which used to hit the same panic. Comptime value params and
> `..$Ts` packs stay exempt. Regression tests:
> `examples/0212-generics-array-arg-slice-param.sx` (scalar/u8/struct
> elements + slice spelling; panicked or mis-typed pre-fix) and
> `examples/1168-diagnostics-generic-param-uninferrable.sx` (string
> arg; panicked pre-fix). Gates: zig build test 426/426, suite 594/594,
> distribution repo 14/14.
## Symptom