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sx/tests/expected/159-pack-generic-ret.txt
agra c917f92509 ffi M5.A.next.2b.fu2.B: generic pack-fn return — infer ret_ty from body
Fix for follow-up #2 from step 2b. When a pack-fn declares
`(..\$args) -> \$R` (return type a generic name), the mono now
infers ret_ty from the body's first explicit `return X;` or
falls back to the tail expression of an arrow-form body.

Plumbing in src/ir/lower.zig:

- `inferPackBodyReturnType(body)` walks the body via the
  existing `findReturnValueType` helper (return stmts) and
  falls through to `inferExprType` on the tail expression for
  arrow-form / tail-expr bodies.
- `monomorphizePackFn` now pre-installs `pack_arg_nodes` and
  `pack_param_count` BEFORE resolving the return type so the
  inference can substitute `args[<lit>]` to call-site arg
  AST nodes during type lookup.
- Generic-ret detection: `fd.return_type` AST node is a
  `type_expr` with `is_generic = true`. Concrete returns stay
  on the standard `resolveReturnType` path.

`examples/159-pack-generic-ret.sx` flips from `0 0` (silent-
zero coercion through opaque struct ret_ty) to `42 99`.

198/198 example tests + `zig build test` green.
2026-05-27 16:28:52 +03:00

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