[clang] [Clang][Sema] placement new initializes typedef array with correct size (PR #83124)

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mahtohappy wrote:

> I definitely agree with both of Shafik's comments!
> 
> The fix itself concerns me, the logic in the block that is having its condition inverted is specifically made for 'if no array size was specified' (see comment), so that makes me think this is an incorrect patch. It doesn't seem to follow the suggestion given in the original bug either.
I agree with that but this was simpler solution, and it didn't break any testcase so I pushed this solution. 
I had a other solution where the check for typedef was separate condition and that was working as well. But this looked neat to me and didn't break anything so I pushed this one.

https://github.com/llvm/llvm-project/pull/83124