[clang] [Clang] Ensure the instantiation of array initializers for decltype/_typeof operator (PR #133575)

[Younan Zhang via cfe-commits]

zyn0217 wrote:

> I find myself wanting a `RequireCompleteType` (or just `CompletesType` - maybe with asserts that check that the resulting types is indeed complete) overload that does not take a diagnostic. `getCompletedType` does not make it clear what it does. And comments would help

Humm, I didn't use RequireCompleteType because it is allowed to be incomplete:

https://godbolt.org/z/5s6s7hn7e

https://github.com/llvm/llvm-project/pull/133575