[Bug c/105510] New: [12] error: initializer element is not constant

[570070308 at qq dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105510

            Bug ID: 105510
           Summary: [12] error: initializer element is not constant
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: 570070308 at qq dot com
  Target Milestone: ---

clang can success compile it but gcc can't. MSVC can't too, I'm not sure this
is a bug.
test.c
```
struct Test2
{
    long int x;
    long int y;
};

struct Test
{
    long int x;
    struct Test2 t;
};

struct Test t=(struct Test){1, (struct Test2){3, 4}};
```
gcc version: gcc-11.3 or gcc-12.0.1