DeclEnum

pub fn DeclEnum(comptime T: type) type {
    const fieldInfos = std.meta.declarations(T);
    var enumDecls: [fieldInfos.len]std.builtin.Type.EnumField = undefined;
    var decls = [_]std.builtin.Type.Declaration{};
    inline for (fieldInfos, 0..) |field, i| {
        enumDecls[i] = .{ .name = field.name, .value = i };
    }
    return @Type(.{
        .@"enum" = .{
            .tag_type = std.math.IntFittingRange(0, if (fieldInfos.len == 0) 0 else fieldInfos.len - 1),
            .fields = &enumDecls,
            .decls = &decls,
            .is_exhaustive = true,
        },
    });
}