Comment 2 for bug 137917

Confirmed. I don't think it's a bug that this happens by default, since ':help c.vim' documents ':let c_no_c99=1' as a way to permit C99 standard items and compound literals are new in C99. However, setting c_no_c99 is not sufficient to remove the error highlighting on the braces here, and it should be.

As a workaround, you can run ':let c_no_curly_error=1' before setting the syntax (or in .vimrc).