Syntax error with #if and designated initializer

From the forum: https://sourceforge.net/p/cppcheck/discussion/general/thread/2cc604d687
~~~
struct S { int i; };
struct S s = {
#if 1
            .i = 1,
#endif
};
~~~
~~~
bar.cpp:3:0: error: Syntax error in #if [preprocessorErrorDirective]
#if 1
^
~~~
The tokens `1` and `.` are combined.