subflow invalid branch

// ============================================================================
// Test 305: Subflow with Invalid Branch Reference
// ============================================================================
// Tests that the shape checker validates subflow continuations
// A subflow that references a non-existent branch should fail shape checking
// ============================================================================

const std = @import("std");

// Event with only ONE branch
~event double { value: i32 }
| doubled { value: i32 }

~proc double {
    return .{ .doubled = .{ .value = value * 2 } };
}

// Event to test
~event process { input: i32 }
| final { output: i32 }

// INVALID subflow: references 'tripled' branch but double event has no such branch!
// This should fail shape checking with "Event 'double' has no branch 'tripled'"
~process = double(value: input)
| doubled d |> final { output: d.value }
| tripled t |> final { output: t.value }  // ERROR: 'tripled' doesn't exist!