non byte-aligned nested packed structs

[xxxbxxx]

Zig Version

0.12.0-dev.29+d1788ecdd

Steps to Reproduce and Observed Behavior

    const S = packed struct {
        bit: u1,
        p: packed struct {
            a: u7,
            b: u8,
        },

        var s: @This() = .{ .bit = 0, .p = .{ .a = 5, .b = 6 } };
    };

    const ptr_p_a = &S.s.p.a;
    const ptr_p_b = &S.s.p.b;
    if (@as(u7,5) != ptr_p_a.*) @panic("boom");
    if (@as(u8,6) != ptr_p_b.*) @panic("boom");     // <<< fails

    if (@intFromPtr(&S.s.p.b) - @intFromPtr(&S.s) != 1) @panic("boom");     // <<<< fails

Expected Behavior

To my understanding of https://ziglang.org/documentation/0.11.0/#packed-struct, the test should pass and ptr_p_b should be a simple *u8.

My guess is that maybe the issue is somewhere around the internal representation of the pointer in Sema.structFieldPtrByIndex():

const val = try mod.intern(.{ .ptr = .{
   .ty = ptr_field_ty.toIntern(),
   .addr = .{ .field = .{
       .base = try struct_ptr_val.intern(struct_ptr_ty, mod),      // <<<< not byte aligned
       .index = field_index,
   } },