opaqueTypeAssumeCapacity

fn opaqueTypeAssumeCapacity(self: *Builder, name: String) Type {
    const Adapter = struct {
        builder: *const Builder,
        pub fn hash(_: @This(), key: String) u32 {
            return @truncate(std.hash.Wyhash.hash(
                comptime std.hash.int(@backingInt(Type.Tag.named_structure)),
                std.mem.asBytes(&key),
            ));
        }
        pub fn eql(ctx: @This(), lhs_key: String, _: void, rhs_index: usize) bool {
            const rhs_data = ctx.builder.type_items.items[rhs_index];
            return rhs_data.tag == .named_structure and
                lhs_key == ctx.builder.typeExtraData(Type.NamedStructure, rhs_data.data).id;
        }
    };
    var id = name;
    if (name == .empty) {
        id = self.next_unnamed_type;
        assert(id != .none);
        self.next_unnamed_type = @fromBackingInt(@backingInt(id) + 1);
    } else assert(!name.isAnon());
    while (true) {
        const type_gop = self.types.getOrPutAssumeCapacity(id);
        if (!type_gop.found_existing) {
            const gop = self.type_map.getOrPutAssumeCapacityAdapted(id, Adapter{ .builder = self });
            assert(!gop.found_existing);
            gop.key_ptr.* = {};
            gop.value_ptr.* = {};
            self.type_items.appendAssumeCapacity(.{
                .tag = .named_structure,
                .data = self.addTypeExtraAssumeCapacity(Type.NamedStructure{
                    .id = id,
                    .body = .none,
                }),
            });
            const result: Type = @fromBackingInt(@intCast(gop.index));
            type_gop.value_ptr.* = result;
            return result;
        }

        const unique_gop = self.next_unique_type_id.getOrPutAssumeCapacity(name);
        if (!unique_gop.found_existing) unique_gop.value_ptr.* = 2;
        id = self.fmtAssumeCapacity("{s}.{d}", .{ name.slice(self).?, unique_gop.value_ptr.* });
        unique_gop.value_ptr.* += 1;
    }
}