028 ambiguous without default

// TEST: Multiple disposal options without [!] should error
//
// When multiple events can discharge an obligation and NONE have [!],
// the compiler must error - it can't guess which one to use.

~import "$std/io"

const std = @import("std");

const File = struct { handle: i32 };

~event open { path: []const u8 }
| opened { file: *File[opened!] }

~proc open {
    const f = std.heap.page_allocator.create(File) catch unreachable;
    f.* = File{ .handle = 42 };
    return .{ .opened = .{ .file = f } };
}

// Two discharge options - NEITHER has [!] = ambiguous!
~event close { file: *File[!opened] }

~proc close {
    std.heap.page_allocator.destroy(file);
}

~event flush_close { file: *File[!opened] }

~proc flush_close {
    std.heap.page_allocator.destroy(file);
}

// This should FAIL - auto-discharge can't choose
~open(path: "test.txt")
| opened _ |> _