zig/test/cases/bugs/1322.zig

const std = @import("std");

const B = union(enum).{
    c: C,
    None,
};

const A = struct.{
    b: B,
};

const C = struct.{};

test "tagged union with all void fields but a meaningful tag" {
    var a: A = A.{ .b = B.{ .c = C.{} } };
    std.debug.assert(@TagType(B)(a.b) == @TagType(B).c);
    a = A.{ .b = B.None };
    std.debug.assert(@TagType(B)(a.b) == @TagType(B).None);
}