013 residual does not cover required

✓ Passing Passing: the compiler rejects this program as expected.

Code

// Test 355_013: MUST_ERROR — a `|*` residual does not cover a REQUIRED
//                          branch.
//
// Pins the boundary the rest of the 355 cluster already assumes: `|*`
// routes OPTIONAL branches (355_001/002/005/010 name every required
// branch). A required branch left to the residual is missing coverage,
// not generic routing — the emitter never wires required arms into `|*`,
// so a checker that lets it count passes a program codegen cannot build.
// The refusal is KORU022 at the frontend, not a Zig switch-exhaustiveness
// crash two layers down.

~tor process { value: u32 }
| success u32
| failure string

~proc process|zig {
    if (value > 5) return .{ .success = value };
    return .{ .failure = "small" };
}

~pub tor observe { name: string }
~proc observe|zig {
    _ = name;
}

// 'failure' is required and unnamed — |* cannot stand in for it.
~process(value: 10)
| success _ |> observe(name: "ok")
|* |> observe(name: "residual")

input.kz

Actual compiler output

error[KORU022]: branch 'failure' must be handled but no continuation found
  --> tests/regression/300_ADVANCED_FEATURES/355_OPTIONAL_BRANCHES/355_013_residual_does_not_cover_required/input.kz:27:0

❌ Compiler coordination error: Incomplete branch coverage
   (set KORU_BACKEND_TRACE=1 for the backend return trace)

Error output must contain

branch 'failure' must be handled

Flows

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

process (value: 10)

Test Configuration

MUST_ERROR

← 012 declined panic branch inside an arm 014 panic arm survives residual →