hasUniqueRepresentation incorrectly returns false for packed structs

[matklad]

Zig Version

0.11.0

Steps to Reproduce and Observed Behavior

const std = @import("std");
const assert = std.debug.assert;

const S = packed struct(u8) {
    @"0": bool,
    @"1": bool,
    @"2": bool,
    @"3": bool,
    @"4": bool,
    @"5": bool,
    @"6": bool,
    @"7": bool,
};

comptime {
    // This fails, but it should pass, `S` is an `u8` in disguise.
    assert(std.meta.trait.hasUniqueRepresentation(S));
}

Expected Behavior

hasUniqueRepresentation returns true for S.

It seems that packed structs should be specially handled over here:

zig/lib/std/meta/trait.zig

Lines 563 to 573 in aeadcb3

	.Struct => |info| {
	var sum_size = @as(usize, 0);
	inline for (info.fields) |field| {
	const FieldType = field.type;
	if (comptime !hasUniqueRepresentation(FieldType)) return false;
	sum_size += @sizeOf(FieldType);
	}
	return @sizeOf(T) == sum_size;
	},