Union

    pub const Union = struct {
        layout: ContainerLayout,
        tag_type: ?type,
        /// Always `null` if `layout != .@"packed"`.
        backing_integer: ?type,

        field_names: []const [:0]const u8,
        /// Guaranteed to have the same length as `field_names`.
        field_types: []const type,
        /// Guaranteed to have the same length as `field_names`.
        field_attrs: []const FieldAttributes,

        decl_names: []const [:0]const u8,

        pub const FieldAttributes = struct {
            /// `null` means the field alignment is not explicitly specified. The field will still
            /// be aligned to at least `@alignOf` the field type.
            @"align": ?usize = null,
        };
    }