[clang] [clang] Only propagate AtStartOfLine when expanding token stream and hit the end of TokenLexer (PR #173052)

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yronglin wrote:

> https://lab.llvm.org/buildbot/#/builders/144

The failure and current PR is not the same issue. This PR fixes extra whitespace before token. I think I have found the root cause of the crash.

https://github.com/llvm/llvm-project/pull/173052