040 undisposed nested obligation

// Library module: fs with nested obligations
// Tests that nested obligations are tracked correctly

const std = @import("std");

const File = struct { handle: i32 };
const Data = struct { content: []const u8 };

// Open a file - returns opened! state
~pub tor open { path: string } -> *File<opened!>

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

// Read - requires an opened file, returns data! state (nested obligation).
// Input is a STATE REQUIREMENT (<opened>), never an issue: `<opened!>` on an
// input parameter is illegal polarity (KORU033, pinned by 330_110) — only
// outputs issue obligations.
~pub tor read { file: *File<opened> } -> { file: *File<opened!>, content: *Data<data!> }

~proc read|zig {
    const d = std.heap.page_allocator.create(Data) catch unreachable;
    d.* = Data{ .content = "test content" };
    return .{ .file = file, .content = d };
}

// Close file - consumes opened!
~pub tor close { file: *File<!opened> }

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

// Free data - consumes data!
~pub tor free { content: *Data<!data> }

~proc free|zig {
    std.heap.page_allocator.destroy(content);
}