[clang] [Clang][Sema] Mark decomposition decl invalid for explicit array type (PR #210964)

[Shengxin Pei via cfe-commits]

TPPPP72 wrote:

@cor3ntin So, I just tested it, and it turns out this introduces a regression; it seems that certain error-reporting mechanisms rely on `D` not being set to an invalid type. Therefore, adding a check for array appears to be the best solution for now.

https://github.com/llvm/llvm-project/pull/210964