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 { value: i32 }
| done { final: i32 }

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

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

[PHASE 2.4] Calling run_pass for transforms\n[PHASE 2.5] Executing comptime_main() - running comptime flows
[PHASE 2.5] Comptime flows complete (33 items)
[PHASE 2.6] Rescanning transformed AST (33 items)
[PHASE 2.6] Rescan complete: 25 comptime events found
  [0] std.compiler:requires
  [1] std.compiler:flag.declare
  [2] std.compiler:command.declare
  [3] std.compiler:coordinate
  [4] std.compiler:context_create
  [5] std.testing:test
  [6] std.testing:validate_mocks
  [7] std.testing:test.with_harness
  [8] std.testing:test.harness
  [9] std.testing:assert
  [10] std.testing:test.property.equivalent
  [11] std.deps:deps
  [12] std.deps:requires.system
  [13] std.deps:requires.zig
  [14] std.control:if
  [15] std.control:for
  [16] std.control:capture
  [17] std.control:const
  [18] std.build:requires
  [19] std.build:variants
  [20] std.build:config
  [21] std.build:command.sh
  [22] std.build:command.zig
  [23] std.build:step
  [24] std.template:define
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:9469:17: 0x1020ee433 in emit (backend)
                return error.CompilerCoordinationFailed;
                ^
/Users/larsde/src/koru/tests/regression/000_CORE_LANGUAGE/040_CONTROL_FLOW/206_label_scope_errors/backend.zig:9553:28: 0x1020ef1bf in main (backend)
    const generated_code = try RuntimeEmitter.emit(compile_allocator, final_ast);
                           ^

Test Configuration

MUST_FAIL
← nested labels arbitrary label jumps →