045 transform optional terminal noop banned

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

Code

// RULING 1 (KORU054) under a transform head — the terminal half of 220_043.
//
// A no-op `_` body on an OPTIONAL terminal branch is illegal even when the
// arm rides a comptime transform: `run` borrows `step`'s arm vocabulary, so
// `done`'s optionality is declared on the sibling decl in the same module.

~pub tor step {}
! ?tick i64
| ?done

~proc step|zig { return .{ .done = .{} }; }

~[comptime|transform]pub tor run { expr: Expression, item: *const std/compiler:Item, program: *const std/compiler:Program } -> SiteResult

~proc run|zig {
    const ast = @import("ast");
    const allocator = @import("std").heap.page_allocator;
    const flow = if (item.* == .flow) &item.flow else return .{};
    return .{ .replacement = ast.Item{ .inline_code = .{ .code = "// run ran", .location = flow.location, .module = allocator.dupe(u8, flow.module) catch return .{} } } };
}

~run()
| done _ |> _

input.kz

Actual compiler output

error[KORU054]: no-op `_` body on optional terminal branch 'done' — arming an optional outcome only to discard it is pure noise
  --> tests/regression/200_COMPILER_FEATURES/220_FLOW_CHECKER/220_045_transform_optional_terminal_noop_banned/input.kz:23:0
    |
 23 | | done _ |> _
    | ^
  hint: omit the arm entirely — an unarmed optional branch already discards the outcome. A no-op is also a hazard: if 'done' is later promoted to REQUIRED, this arm would silently swallow it instead of surfacing the must-handle error. To act, replace `_` with a real step; to intentionally handle-and-ignore, the branch must be REQUIRED (drop the `?`), not optional.

Must fail at frontend compile:

Parsing or type-checking must reject the program.

Error output must contain

KORU054

Flows

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

run

Test Configuration

MUST_ERROR

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