const Allocator = @import("std").mem.Allocator;

pub const Inner = struct {
  allocator: Allocator,
  inner_field: i32,
};

pub const Outer = struct {
  inner: Inner,
  outer_field: i32,

  pub fn init() Outer {
    return Outer{
      .inner = Inner{
        .allocator = Allocator{
          .allocFn = alloc,
          .reallocFn = realloc,
          .freeFn = free,
        },
        .inner_field = 200,
      },
      .outer_field = 100,
    };
  }

  fn alloc(allocator: *Allocator, n: usize, alignment: u29) ![]u8 {
    const inner = @fieldParentPtr(Inner, "allocator", allocator);
    const outer = @fieldParentPtr(Outer, "inner", inner);

    etc...