[clang] Using type deduction to define __SIZE_TYPE__ and __PTRDIFF_TYPE__ (PR #155979)

[via cfe-commits]

YexuanXiao wrote:

> If you want __size_t you should just set it to __size_t. I don't see what the point of this approach is other than risking causing issues due to it not just being a plain specifier qualifier list.

Because __size_t is not a keyword, it cannot be directly accessed through user code.

https://github.com/llvm/llvm-project/pull/155979