129 call in produce expression

✓ Passing This code compiles and runs correctly.

Code

input.k

Frontend must reject with:

CONTAINS error[KORU104
CONTAINS nested call
CONTAINS chain

Error Verification

Expected Error Pattern

A call inside a PRODUCE (->) expression is illegal — calls are not
expressions; the idiom is bind-first (`g(a: 4): x -> 1 + x`).

Guarded by the KORU104 expression-admission wall (flow_checker, Stage A).
Bare-return impls parse as `immediate_impl` items (not flows) with the
produce text in value.plain_value — the wall walks those items explicitly.
Previously the call leaked verbatim into emitted Zig (raw Stage-D error).

Actual Compiler Output

error[KORU104]: nested call in a produce (`->`) expression — calls are not expressions; use event chaining: bind the result first
  --> tests/regression/320_CONTROL_FLOW/320_129_call_in_produce_expression/input.k:17:0
    |
 17 | 
    | ^
  hint: rewrite as `event(args): x |> ...` and use `x` here

Flows

flow ~outer click a branch to expand · @labels scroll to their anchor
outer

Test Configuration

MUST_FAIL