label scope errors

✓ Passing This code compiles and runs correctly.

Code

// ============================================================================
// VERIFIED REGRESSION TEST - DO NOT MODIFY WITHOUT DISCUSSION
// ============================================================================
// Test 206: Label scope errors
// Tests that labels are flow-scoped and cannot be accessed across flows
// Expected to fail compilation with "Unknown label 'loop'" error
// ============================================================================

const std = @import("std");

// Simple counter event
~event counter { n: i32 }
| next i32
| done i32

~proc counter {
    std.debug.print("Count: {}\n", .{n});

    if (n < 3) {
        return .{ .next = n + 1 };
    } else {
        return .{ .done = n };
    }
}

// Start event
~event start {}
| ready

~proc start {
    std.debug.print("Starting...\n", .{});
    return .{ .ready = .{} };
}

// Flow 1 with a label
~start()
| ready |> #loop counter(n: 1)
    | next c |> @loop(n: c.value)
    | done |> _

// Flow 2 trying to jump to Flow 1's label (should error!)
~start()
| ready |> @loop(n: 1)  // ERROR: 'loop' is not in scope here
input.kz

Error Verification

Expected Error Pattern

Label Scope Validation Test

This test MUST FAIL to verify that labels are flow-scoped.

Expected behavior:
- Flow 1 defines label 'loop'
- Flow 2 tries to jump to 'loop' which is out of scope
- Shape checker should reject this with "Unknown label 'loop'"

This validates that label scope checking is working correctly in the backend.

Actual Compiler Output

error[KORU041]: unknown label '@loop'
  --> structural_check:44:0

❌ Compiler coordination error: Unknown label referenced
error: CompilerCoordinationFailed
/Users/larsde/src/koru/tests/regression/000_CORE_LANGUAGE/040_CONTROL_FLOW/206_label_scope_errors/backend.zig:9475:17: 0x100d924af in emit (backend)
                return error.CompilerCoordinationFailed;
                ^
/Users/larsde/src/koru/tests/regression/000_CORE_LANGUAGE/040_CONTROL_FLOW/206_label_scope_errors/backend.zig:9559:28: 0x100d932b7 in main (backend)
    const generated_code = try RuntimeEmitter.emit(compile_allocator, final_ast);
                           ^

Test Configuration

MUST_FAIL